ALBERT

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Description: A novel planar multilayered epsilon-near-zero (ENZ) tunnel sensor based on fully laminated surface integrated waveguide (SIW) technology is proposed for the microwave measurement of dispersive materials. The proposed sensor is designed and optimized using parametric analysis to obtain the multilayered ENZ tunnel dimensions. It is observed that the width of the upper tunnel of the designed two-tunnel sensor should be at least half of the SIW width of the actual SIW structure for the multiband operation. The complex permittivity measurement using the proposed sensor is possible at two frequencies with a single set of measurement data. The proposed method is based on perturbation of the squeezed electric field having constant magnitude and high intensity inside the multilayered ENZ tunnel, which eventually increases the sensitivity of the proposed sensor. The sensitivity and accuracy of the proposed sensor are tested using both the simulated and the experimented data. It is found that the proposed sensor is highly sensitive, and typically demonstrates 6% error under ideal conditions, thus making it a good candidate for the microwave measurement of dispersive materials.

Description: This paper presents a new approach for the definition and identification of a transistor model suitable for low-noise amplifier (LNA) design. The resulting model is very robust to layout modifications (i.e., source degeneration) providing accurate predictions of device noise-performance and small-signal parameters. Moreover, the described procedure is very robust since it does not require any numerical optimization, with possibly related problems like local minima and unphysical model parameters. The adopted model topology is based on a lumped element parasitic network and a black-box intrinsic device, which are both identified on the basis of full-wave electromagnetic simulations, as well as noise and ${ S}$ -parameter measurements. The procedure has been applied to three GaN HEMTs having different peripheries and a Ku-band LNA has been designed, demonstrating a very good agreement between measurements and predicted results.

Description: Novel design of a shielded vertically stacked ring resonator (VSRR) is presented in this paper. The use of a shielded VSRR with a layer of the low-loss liquid that fills the partial space between the fed patch and the parasitic patch have been investigated. Dependencies of the resonating frequency and input impedance of the shielded VSRR on structure size and material properties of the test liquid layer are discussed. The method, of finding the complex permittivity (CP), particularly of petroleum liquids, is verified using electromagnetic modeling with full wave simulation software ANSYS HFSS-15 and confirmed experimentally. The proposed new design of the resonator will improve the sensitivity of single ring boxed resonator in terms of the quality factor, and in turn, increase the CP measurement sensitivity.

Description: This paper proposes a design scheme for extending the bandwidth of a three-stage Doherty power amplifier (DPA) based on symmetric devices for broadband applications. The proposed bandwidth enhancement scheme provides an optimized solution for the load combiner parameters while operating the auxiliary power amplifier (PA) at lower current values as compared to the main PA at saturation. The proposed scheme promises 30.3% fractional bandwidth in terms of efficiency enhancement up to 9.54-dB back-off. The proposed design methodology is validated with the design of a broadband three-stage DPA using three 10-W packaged GaN HEMT devices. Measurement results show more than 51.6% drain efficiency at 6-dB output power back-off (OPBO) over the entire frequency range from 700 to 950 MHz. At 9.54-dB OPBO, the drain efficiency is better than 50.2% over this 250-MHz band. The peak drain efficiency at saturation is better than 60.04% over the entire band of operation. Measurement with 5-MHz WCDMA modulated signal shows the average drain efficiency of about 57.6% at 33.97-dBm average output power at the center frequency of operation. The corresponding adjacent channel power ratio is better than ${-}{hbox{45.6}}$ dBc after applying digital predistortion. The circuit is realized with microstrip technology, which can be easily fabricated using conventional printed circuit processes.

Description: In this work, the design of an inductorless, high-isolation, and high conversion gain fully differential subharmonic down-conversion mixer for 2.4-GHz wireless application is presented. A complementary current-reuse technique is adopted between the transconductance and the local oscillator (LO) switching stage to boost the conversion gain without additional power consumption in the concept of reusing the dc current of the LO switching stage. The LO switching transistors are driven by a 25% duty cycle input to further enhance the conversion gain and improve the noise-figure performance. An active balun is integrated in the design for single-balanced to differential conversion or vice-versa, along with an RC poly phase filter to generate quadrature LO signals from a differential input signal. The subharmonic mixer is fabricated in a 0.13- $mu{hbox{m}}$ standard CMOS technology with a core chip dimension of 313 $mu{hbox{m}}times,$ 372 $mu{hbox{m}}$ and a power consumption of 5.82 mW from a supply voltage of 1.2 V. Experimental results show a conversion gain of 13.61 dB, an input-referred third-order intercept point of $-{hbox{4.46 dBm}}$ , a noise figure of 20 dB, and an isolation greater than 50 dB between the LO, RF, and IF ports. The proposed inductorless subharmonic mixer has a competitive performance in size with high isolation performance and highest conversion gain in comparison to other published works.

Description: This paper presents a novel method to design filtering rat-race hybrids with wide-stopband bandpass responses. Four ${pm} K$ -inverters with bandpass functions are utilized to replace the one or three quarter-wavelength transmission lines in the conventional rat-race hybrid. The ${pm} K$ -inverters consist of transmission lines and capacitors, which can reduce the area occupied and suppress the high-order harmonics. Furthermore, the isolation performance is enhanced by embedding the ${pm} K$ -inverters. Theoretical analysis is carried out and design equations are derived. For demonstration, a filtering rat-race hybrid with bandpass responses is implemented. The center frequency is located at 470 MHz with the insertion loss of 1.2 dB. Good in-phase and out-of-phase characteristics are observed. Comparisons between the measured and simulated results are also presented to verify the theoretical analysis. The overall size is only 4.6% of the conventional hybrid and stopband is extended to $5f_{0}$ .

Description: An approach that can be used for exploiting the sensing capabilities of RF identification (RFID) is presented and formulated. In this approach, sensor information is carried through the modulation frequency of RFID. The aim of this work is to investigate the sensor concept and to characterize the sensor performance both theoretically and experimentally. Furthermore, the operation of the sensor RF parts and oscillator are described analytically, and the equations are verified by simulations and measurements. The concept is experimentally demonstrated at a single carrier frequency to test its suitability for ultra-high-frequency RFID applications, and shown to be feasible for implementing sensors that can be read across distances up to 14 m.

Description: Based on advanced industrial fabrication processes and on specialized design strategies, a new class of ferroelectric metal–insulator–metal (MIM) capacitors with high tunability and high quality factor ( $Q$ -factor) is here presented. Modeled by means of lumped element equivalent circuits and experimentally validated up to 67 GHz, a maximum tunability of 81% (0–20-V bias), and a $Q$ -factor improvement up to 30% (at 0 V) could be demonstrated at 1 GHz. These varactors have been exploited in the design of reconfigurable filters, with a center frequency at around 1 GHz that can be tuned up to 112%, and a figure of merit (FoM) per applied bias better than ${hbox{31.5}}~{hbox{dB}}^{-1} /{hbox{kV}}$ . Owing to their promising features, these materials have been exploited to design small-size capacitors suitable for millimeter-wave frequencies. The results demonstrate tunabilities and FoMs superior to the state-of-the-art. Based on this, two 60-GHz tunable phase shifters are proposed. They represent the first example of such devices based on MIM $({hbox{Ba,Sr}}){hbox{TiO}}_{3}$ (BST) capacitors. In terms of insertion loss, size, FoM, and FoM per bias they show a remarkable improvement with respect to the state-of-the-art of ferroelectric-based devices, thus proving that the BST represents a promising candidate to operate into the millimeter frequency band.

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Description: The development of thin microwave absorber coatings that operates for a wide range of frequencies is still a challenging task. This work presents a technique of blending a fractal frequency selective surface (FSS) with single- and double-layer coatings. These coatings are comprised of well-optimized micrometer-sized (80–90 $mu{hbox{m}}$ ) and nano-sized (20–30 nm) Ti particles based ${hbox{Fe}}_{3} {hbox{O}}_{4}$ (80–100 nm) composites. The main objective of this study is to achieve good absorption with wide bandwidth corresponding to ${hbox{reflection loss (RL)}}~ le 10~{hbox{dB}}$ for less coating thickness ( $le {hbox{1.5 mm}}$ ). Waveguide measurements are carried out to obtain the effective complex dielectric permittivity ( $varepsilon_{ r} =varepsilon_{ r}^{prime}-{ j}varepsilon_{ r}^{prime prime}$ ) and effective complex magnetic permeability ( $mu _{ r} =mu_{ r}^{prime}-{ j} mu_{ r}^{prime prime}$ ) values of ${hbox{Fe}}_{3} {hbox{O}}_{4}$ -Ti based heterogeneous composites. The measured $varepsilon_{ r}^{prime}$ , $varepsilon_{ r}^{prime prime}$ , $mu_{ r}^{prime}$ , and $mu_{ r}^{prime prime}$ values are used for the designing of double-layer composite absorbers, where the suitable composite se- ection, layer preferences, as well as thickness of layers are optimized using a genetic algorithm. The fractal geometry based FSSs have been designed using an iterated function system, which are embedded with single- and double-layer composite absorbers to examine their effect on absorption. A double-layer composite coating with a Sierpinski gasket fractal FSS shows a strong RL of 35.57 dB at 9.5 GHz with broad bandwidth of 4.2 GHz in the range from 8.2 to 12.4 GHz. The total coating thickness is only 1.4 mm. Findings provide an effective and feasible way to develop thin and broadband absorber coatings for various practical applications.

Description: In this paper, an alternative perspective on the transmission line modeling (TLM) method concepts to unify previous work is presented. The procedure begins by discretizing Maxwell’s equations and proposing TLM equivalent models. Node voltage and mesh current definitions are provided in terms of link line contributions, compatible with stub currents and voltages. They allow obtaining an expression that relates incident and reflected pulses with no other condition required. With this unified approach, modeling of other situations is straightforward. 2-D cases, source implementation, and anisotropic media are described and numerically tested.

Description: Gyrotrons are the only RF sources providing significantly high output powers at continuous-wave operation in the sub-terahertz frequency range. A prerequisite for a proper study of gyrotron behavior is the accurate time-dependent self-consistent simulation of the interaction between the electron beam and the RF wave inside the interaction region (cavity). That requires an accurate description of the RF fields at the boundaries of the interaction region. In this work, an improved broadband boundary condition is proposed. Based on polynomial series expansion of the load impedance and of the wavenumber, this boundary condition not only features a significantly improved broadband matching, but also allows a customizable frequency-dependent reflection coefficient at the boundaries. The boundary condition has a general formulation, i.e., it does not rely on a special numerical method. For the case of perfect matching, the new formulation is validated through comparing the numerically calculated reflection coefficients with those obtained by the state-of-the-art matched gyrotron broadband boundary condition, whereas the validation in the case of a given frequency-dependent reflection is done by comparing the numerically calculated reflection with the prescribed one. Although this concept is initially intended for the simulation of gyrotron cavities, it can be easily extended to any other open-cavity resonators, for which proper definition of the boundary conditions is required.

Description: A semi-analytical approach, relying on the mode-matching method and the resonator technique, is proposed. It is conceived to evaluate the performance of mode filters, based on corrugations partially filled with an absorbing material, in the case of oversized rectangular waveguides. The mathematical formulation allows an accurate and fast computation of the scattering parameters, through closed-form expression of the surface integrals and some matrix algebra. The theoretical model is implemented in a code that is benchmarked against a finite-element method to elucidate its advantages with respect to volumetric solvers. After giving an insight on the physical mechanisms ruling the performance of these devices, the modal method is used to run the particle swarm optimization algorithm for different types of devices, taking advantage of the reduced computation time of the developed tool.

Description: This paper presents the design and fabrication of a broadband microstrip attenuator, operating at 1–20 GHz, based on few layer graphene flakes. The RF performance of the attenuator has been analyzed in depth. In particular, the use of graphene as a variable resistor is discussed and experimentally characterized at microwave frequencies. The structure of the graphene-based attenuator integrates a micrometric layer of graphene flakes deposited on an air gap in a microstrip line. As highlighted in the experiments, the graphene film can range from being a discrete conductor to a highly resistive material, depending on the externally applied voltage. As experimental evidence, it is verified that the application of a proper voltage through two bias tees changes the surface resistivity of graphene, and induces a significant change of insertion loss of the microstrip attenuator.

Description: A tunable highly integrated bandpass–bandstop filter (BSF) cascade that is capable of dynamically relocating its transmission zeros arbitrarily close to its passband without causing parasitic resonances and additional mismatch loss is demonstrated in this paper. An arbitrary phase BSF that enables a compact cascade topology and an extension of the classical coupling matrix synthesis for filters terminated with a complex impedance are the key advantages of the proposed bandpass–BSF cascade. Independent and simultaneous tuning of the passband center frequency, bandwidth, and transmission zeros are possible in this topology. The proposed cascade synthesis approach is experimentally validated using commercially available lumped elements. In these implementations the transmission zeros can be placed on the skirt of the bandpass filter and can be used to create high isolation (50-dB notch 4.7% away from the passband edge), increase the selectivity of the passband, and tune the fractional bandwidth from 3% to 9% without additional mismatch loss.

Description: In this paper, a balanced-to-unbalanced microstrip power divider based on branch lines with several stubs and one resistor is proposed. The functions of power dividing, frequency selectivity, isolation between output ports, and common-mode suppression can be realized at the same time. The even–odd-mode equivalent circuits combining with the standard S-parameters and the mixed-mode S-parameters are adopted to derive the analytical equations at the center frequency. One or two transmission zeros can be achieved to enhance the out-of-band suppression. The center frequency, bandwidth, isolation, common-mode suppression, and the frequencies of transmission zeros can be controlled by the design procedure. To verify the theoretical prediction, two fabricated prototypes are designed and compared. One gets 7.7% 1-dB bandwidth with 0.6-dB insertion loss and one transmission zero. The other gets 1-dB bandwidth of 5% with 0.7-dB insertion loss and two transmission zeros. The isolation and common-mode suppression for both prototypes are better than 15 and 20 dB within the whole passband, respectively.

Description: The pulse-modulated polar transmitter (PMPT) uses the envelope information to pulse modulate the phase information to implement a highly linear and highly efficient polar transmitter. The bandwidth of the PMPT is primarily determined by the pulsewidth modulation sampling frequency of the envelope information. For wide bandwidth applications such as long-term evolution (LTE), finite rise and fall times of the RF pulses distort the envelope information. In this paper, the nonideal RF pulses are analyzed and an envelope correction method is proposed to reduce the distortion in wide bandwidth applications using the PMPT architecture. For validation, a cellular-band prototype transmitter system was constructed using commercially available components. Using a 20-MHz bandwidth 16-QAM LTE signal at 836.5 MHz, the prototype transmitter achieved an output power of 22.7 dBm and drain efficiency of 33% while passing the spectral requirements of the LTE standard.

Description: In this paper, a new topology using the common-source amplifier, which is a unilateral component and the directional coupler, is proposed to realize an isolator without ferrite. The theory and the design procedures are presented. The performance of this isolator is comparable to those of the ferrite isolators, except for the bandwidth. The 1-dB compression point of output power $({rm OP}_{1{rm dB}})$ of the insertion loss is high due to the passive nature of the directional coupler, but the reverse isolation deteriorates with the increasing input power. The proposed 24-GHz monolithic microwave integrated circuit isolator is developed in TSMC 180-nm CMOS. Based on the proposed isolators, a quasi-circulator is designed and fabricated. Both the isolator and quasi-circulator have better ${rm OP}_{1{rm dB}}$ of the insertion loss than reported active isolators and quasi-circulators.

Description: This paper presents a fully integrated W-band 4-GHz bandwidth (BW) pseudo-noise (PN)-coded pulse compression radar transmitter (TX) in a CMOS technology. The PN-coded pulse compression scheme is adopted to obtain high spectral density and to lower the TX leakage using a 63-bit PN code generator based on linear feedback shift registers. We propose a sub-harmonic pumped pulse former and a pulsed power amplifier for high TX efficiency with the suppression of local oscillator (LO)/2LO leakage. A frequency synthesizer including a frequency divider chain generates a sub-harmonic LO signal, as well as a 5-GHz digital clock. Digital blocks with the PN-code generator are synchronized with the clock signal, which makes all pulses start with the same phase. The proposed TX achieves 14.5-dBm maximum output power with the tuning range of 75–81.5 GHz, and the phase noise is ${-}{hbox{95.2}}$ dBc/Hz at a 1-MHz offset in the range of LO frequencies. In pulse mode, it generates a 4-GHz BW RF pulse signal, which corresponds to a range resolution of 7.5 cm, and the average dc power dissipation is 160 mW.

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Description: In the above paper, the author presents the theoretical analysis of a single-ended Class ${hbox{E}}/{hbox{F}}_{n}$ mode with explicit derivation of the idealized optimum voltage and current waveforms and load-network parameters with their verification by time- and frequency-domain simulations for a particular case of Class ${hbox{E}}/{hbox{F}}_{3}$ mode with a 50% duty cycle. However, some errors have been found which may affect the readers understanding, and they will be clarified in this letter.

Description: In this study, the finite-element method is applied to reconstruct the electrical properties (conductivity and permittivity) maps of media with 1-D, 2-D, and 3-D inhomogeneities based on the RF magnetic field distributions in a magnetic resonance imaging (MRI) system. The proposed method handles the discontinuity of electrical properties well. It therefore shows high accuracy at the boundary compared to retrieval methods in the literature. The method has successfully been validated using both analytical and numerical data. Moreover, the noise sensitivity of the proposed method is studied. Good accuracy of retrievals can be obtained when proper coils are chosen (e.g., transverse electromagnetic coils). It is an effective approach showing one step further towards accurate electrical property mapping based on MRI data. It helps to pave the way to accurate calculations of specific absorption rate distributions and temperature distributions of human body under MRI scans, which are crucial for the evaluation of the safety of MRI systems. Moreover, the increased accuracy of the electrical property maps of human body show their potential to be a diagnostic tool for tumors and cancers, especially at their early stages. Following-up research is expected to make the proposed method robust and practical for clinical applications.

Description: A new methodology for the design of single/multi-band power amplifiers (PAs) with dynamic load modulation (DLM) is presented. First, the topology for the output matching network (OMN) including the control varactor is selected. A comprehensive optimization of the OMN parameters is then developed by which varactor and transistor losses are considered to ensure maximum efficiency enhancement at each frequency. To verify the method, a dual-band PA with DLM is realized. Drain efficiencies of 75% and 60% at 685 MHz and 1.84 GHz, respectively, are measured at peak output power. At 10-dB output power back-off efficiencies of 43.5% and 49.5%, respectively, are obtained. Linearized modulated measurements with a 6.5-dB peak-to-average power ratio WCDMA signal show average drain efficiencies of 56% and 54% at 685 MHz and 1.84 GHz, respectively, at an adjacent channel leakage ratio of $-{hbox{49}}$ and $- {hbox{47.5 dBc}}$ , respectively. The proposed method shows the effectiveness of applying an optimization process for the design of single- or multi-band DLM PAs. The results demonstrate that near-optimum performance may be obtained in terms of efficiency enhancement for a given transistor and varactor-based OMN, thus making DLM competitive against other load modulation techniques.

Description: This paper presents an envelope tracking (ET) transmitter architecture based on the combination of a novel 3-bit $(N = 3)$ supply modulator and digital predistortion (DPD). The proposed power converter is based on a direct digital-to-analog conversion architecture that implements the binary-coded sum of $N$ isolated dc voltages, allowing the synthesis of an output waveform with $L = 2^{N}$ voltage levels, with a binary distribution in the range $Delta V = V_{M} - V_{O}$ (maximum voltage $V_{M}$ , offset voltage $Vo$ ). This solution provides a better voltage resolution $V_{S} = Delta V/(2^{N}-1)$ with respect to typical multilevel switched-sources topologies $(V_{S} = Delta V/N)$ . The improved voltage resolution enables the correction of the residual discretization error in the ET transmitter by means of DPD of the RF signal without the need of an auxiliary linear envelope amplifier. The proposed ET solution has been tested with an L-band 30-W lateral-diffused MOS RF high power amplifier (RF HPA) with 1.4- and 10-MHz long-term-evolution signals. In these conditions the converter demonstrated 92% and 83% efficiency, respectively, whereas the congregate efficiency of the transmitter are 38.3% and 23.9% at 5.5 and 1.9 W of average RF output power, respectively. These performances correspond to an improvement of 17.2 and 17.9 points for the power-added efficiency of the RF HPA and to 13.4 and 13 points of improvement for the efficiency of the enti- e transmitter with respect to fixed bias operation.

Description: In this paper, a novel 8-phase-shift-keying (8-PSK) carrier recovery and demodulation method using a comparator and frequency divider is proposed. A proof-of-concept 8-PSK demodulator for high-data-rate millimeter-wave communication systems is designed and tested, which can support 8-PSK transmission up to 15 Gb/s with a bit error rate less than ${hbox{10}}^{-7}$ .

Description: This paper presents a CMOS broadband programmable gain active balun (PGAB) that demonstrates seven digitally controlled gains with 0.5-dB gain steps separately for plus and minus output ports. The PGAB was designed and fabricated in a 130-nm RFCMOS process. For the maximum gain state, the measured gains of the plus and minus ports are 0.0 and 1.1 dB at 2 GHz. The operating frequency range is from 1.0 to 8.0 GHz by 0.3-dB gain step error, and it is from 1 to 13.0 GHz by 3-dB gain attenuation. For the maximum gain state, the measured amplitude imbalance and phase imbalance from 1 to 16 GHz are less than 1.4 dB and 4.1 $^{circ}$ , respectively. The measured input return losses are better than 13.5 dB, and the output return losses are better than 18.5 dB for all controlled gain states from 1 to 16 GHz. The measured IP1dB at 7 GHz is 6.1 dBm. The measured noise figures for the plus and minus ports from 2 to 14 GHz are less than 11.2 and 10.2 dB, respectively. The supply voltages are 3.0 and 1.5 V, and the measured power consumption is 93 mW. The core area of the fabricated integrated circuit is 0.38 mm $,times,$ 0.36 mm.

Description: This paper presents the design and analysis of a single-compound complementary split-ring resonator (SC-CSRR) that induces two resonance frequencies for simultaneously measuring the thickness and permittivity of dual-layer dielectric structures. Two resonance frequencies were generated using two distinct embedded resonator current lengths in a single complementary split-ring resonator. These two resonance frequency responses were combined to determine the thickness and permittivity of a dual-layer dielectric sample. Methods proposed in this paper were used to analyze the equivalent permittivity relationship, and thus, determine the thickness and permittivity of the material under test. The proposed simple low-cost SC-CSRR measurement method for assessing the permittivity of materials in a compact area was experimentally analyzed and verified in experiments. The experimental results indicated that the average thickness and permittivity measurement errors were 6.26% and 4.63%, respectively, for single-layer samples, and 5.26% and 6.48%, respectively, for dual-layer samples.

Description: Pulsed electric fields of sufficient magnitude and duration trigger functional responses and modifications in biological cells. Transient nanometer-sized pores are believed to form within nanoseconds in cell membranes exposed to high-intensity (MV/m) nanosecond pulsed electric fields (nsPEFs), and while it is clear that polar water molecules play a key role in electroporation, no signature for pore initiation has yet been identified. To address this, we combine molecular dynamics simulations and quasi-static 3-D finite-difference analysis to investigate the electrostatic interactions that drive pore formation in homogenous lipid bilayers exposed to intense nsPEFs. The developed methodology uniquely enables the extraction of 3-D spatiotemporal profiles of electric potentials, electric fields, and electric field gradients in biological membranes with atomistic detail and sub-nanosecond resolution. As a result, this study captures and elucidates several dynamic phenomena observed experimentally and provides a fundamental framework for further development.

Description: A new compact low-loss fast phase-shift high-power microwave (HPM) phase shifter (PS) is proposed, designed, and cold and high-power tested. Firstly, based on solving the scattering matrix and eigenvectors, we design a novel HPM dual circular polarizer, and then a dumbbell-like metal plug driven by a high-speed servomotor is used to slide a short circuit along the dual circular polarized port to adjust the output RF phase, which varies 180 $^{circ}$ by moving the plug with a quarter of the guided wavelength. The X-band PS has a total length of 9.5 cm and a power capacity achieved 300 MW at 30-ns HPM pulse. A fast phase shift of 310 $^{circ}$ was achieved within 0.1 s in test, a high precision of phase shift 1 $^{circ}$ can be realized, and the tested insertion loss was $〈$ 0.15 dB.

Description: This paper presents a novel tunable dual-band bandstop filter based on doubly tuned RF transformers. This design results in two distinct notch frequencies in a single resonator using silicon varactor diodes. The 2-pole tunable dual-band bandstop filters are implemented using printed circuit board (PCB) transformers and air-coil transformers. With PCB transformers, the lower frequency can be tuned at 513–845 MHz while the higher frequency can be tuned at 715–1151 MHz with a ${hbox{notch level}} 〉 16~{hbox{dB}}$ . With air-coil transformers, a single-band 2-pole notch filter with wide rejection bandwidth is achieved. The design results in 604–982 MHz tuning with a 20-dB rejection bandwidth of 27–45 MHz. Also, by implementing a series varactor in a transformer, the separation between two coupled frequencies can be changed. The topology can be easily extended to higher order filters and design equations are presented.

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Description: This paper reports on an ultra-low phase-noise oscillator based on a GaN HEMT monolithic microwave integrated circuit reflection amplifier and an aluminum cavity resonator. It is experimentally investigated how the oscillator’s phase noise depends on the cavity coupling factor, phase matching, and bias condition of the reflection amplifier. For the optimum bias and cavity position phase noise of $-{hbox{145}}$ dBc/Hz and ${-{hbox{160}}}$ dBc/Hz at offsets of 100 and 400 kHz, respectively, from a 9.9-GHz carrier frequency is reached. This is, to the best of the authors’ knowledge, a record in reported performance for any oscillator based on a GaN HEMT device. The optimum performance at 400-kHz offset corresponds to a power normalized figure of merit of 227 and compensating for finite efficiency in the reflection amplifier, the achieved result is within 7 dB from the theoretical noise floor, assuming a linear theory.

Description: The dual wavelength linearization (DWL) technique using two lasers with different wavelengths is for the first time comprehensively studied theoretically and experimentally to improve output signal power and suppress second- and third-order nonlinearities in radio-over-fiber (RoF) systems using an electro-absorption modulator (EAM). Spurious-free dynamic ranges (SFDRs) are calculated and measured. Both the calculation and experiments show that not only the RF signal power is significantly increased, but also both the second- and third-, as well as fifth-order nonlinearities are suppressed. For our considered EAM, when the second-order nonlinearity is suppressed maximally, the SFDRs with respect to second-order harmonic distortion and second-order intermodulation distortion are improved by 11.5 and 8.5 dB, respectively. In the mean time, the SFDRs with respect to third-order harmonic distortion (HD3) and third-order intermodulation distortion (IMD3) are improved by 1.8 and 1.3 dB, respectively. When the third order is suppressed maximally, the SFDRs with respect to HD3 and IMD3 are improved by 8.1 and 20.4 dB, respectively. The fifth-order intermodulation distortion is also suppressed at the same time. The RoF transmissions for WiFi signals are also verified. As a result, 3.5 dB at 2.4-GHz improvement and 2.8 dB at 5-GHz improvement of error vector magnitude are obtained for an RoF system by using the DWL technique.

Description: In this paper, we propose a self-directed adaptive phased array control method using the low-frequency part of the signal for a millimeter-wave wireless personal area network, which can reduce the hardware requirement and power consumption compared with those of the conventional digital beamforming method. The signal from each element antenna of the antenna array is phase shifted and down converted to the baseband and then divided into two paths. The first paths are low-pass filtered to extract the low-frequency part of the signals for beamforming control. The second paths from all antennas are combined in-phase in an analog domain and then sampled by two high-speed A/D converters for demodulation. A beamforming algorithm using the sampled low-frequency part of the signal is also proposed. The beamforming calculation time is established as a function of the signal-to-noise ratio, the bandwidth of the low-frequency part, and the required phase control accuracy. The calculated values match the measured results. Using the IEEE 802.15.3c specifications with an eight-element array antenna, the calculation time is less than ${hbox{5}}~mu{hbox{s}}$ for initial beam establishment and less than ${hbox{30}}~mu{hbox{s}}$ for beam tracking. Therefore, high-speed beamforming is possible while reducing the power consumption.

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Description: A novel realization of a broadband $8 times 8$ Butler matrix having phase progressions 0°, ±45°, ±90°, ±135°, and 180° has been proposed. The presented network is composed of coupled-line 3-dB/90° directional couplers and Schiffman phase shifters that ensure its broadband amplitude and phase characteristics. The proposed solution allows for a fully planar realization without any interlayer connections, which has been achieved by both rearrangement of the matrix layout and realization of the selected crossovers as tandem connections of quadrature directional couplers. The proposed concept has been verified experimentally by the design of a Butler matrix operating within 2.5–3.5 GHz and applied in a multibeam antenna array with broadside beam.

Description: This paper expands our previous work on planar tunable capacitive coupling structures in substrate-integrated cavities using lumped components. We demonstrate both frequency and bandwidth tunable filters with adjustable transmission zeros (TZs). By the appropriate choice of the absolute and relative strength of magnetic and electric coupling coefficients, we demonstrate: 1) tunable bandwidth and the ability to maintain either a constant absolute bandwidth or a constant fractional bandwidth; 2) adjustable TZ location at a prescribed bandwidth; and 3) the ability to switch OFF the filter with high isolation. Filter design methodologies based on a dispersive coupling structure are presented using lumped circuit models, coupling matrix, and full-wave simulations. With this planar capacitive coupling, it is also convenient to realize cross-coupling in higher order filters to produce additional TZs for rejecting spurious resonances or interferes. Fabricated two-pole filters with one or two TZs and four-pole filters with three or four TZs validate the filter design. A two-pole filter with tunable center frequency and tunable bandwidth along with a four-pole filter with tunable center frequency and tunable TZs are also demonstrated.

Description: A fully integrated transformer-based quasi-Doherty power amplifier (DPA) with an adaptive power divider (APD) is presented in this paper. A novel folded combining transformer is designed for power combining, which has smaller insertion loss than a conventional one. An APD adaptively controls the power delivered to carrier and peaking amplifiers by altering the input impedance of the peaking amplifier, which has a variable resonance frequency that changes according to the input power. Most of the power is delivered to the carrier amplifier at low incoming power, and it is divided between the carrier and the peaking amplifiers at high incoming power. With continuous wave signal at 1850 MHz, the quasi-DPA implemented with an SOI CMOS process achieves 39.8% and 44.4% power-added efficiencies (PAEs) at the first and the second peak, respectively. With wideband code division multiple access signal, it has 29.2-dBm average linear output power and a 40.47% PAE with a −33-dBc adjacent channel leakage ratio 1. With long-term evolution (LTE) signal, it delivers 27.2-dBm average linear output power and a 37.7% PAE, satisfying linearity requirements for the LTE.

Description: This paper presents a compact high-temperature superconducting (HTS) diplexer using single-resonance and dual-resonance spiral resonators. The single-resonance spiral resonators (SSRs) are used separately in each individual channel of the diplexer, and the dual-resonance spiral resonators (DSRs) are used as common resonators of both channels. DSRs are designed using a modified stub-loaded resonator, which can produce two resonant frequencies for both the channels of the diplexer. Because the SSRs and the DSRs are dissimilar resonators, their different spurious frequencies result in a wide stopband. Moreover, resonators are connected by a novel coupling diagram to ensure both high performance and compact size. The size of the diplexer can be greatly reduced while the isolation is kept well. Based on the method, a diplexer is designed for 1.8-GHz mobile and 2.4-GHz wireless area networks systems. The diplexer is fabricated on a YBa2Cu3Oy polished MgO substrate wafer, which has a compact size of $0.12~lambda g times 0.073~lambda g$ . The measured frequency responses agree well with the simulated results. The isolations in both channels are larger than 39 dB, and the measured insertion losses of both channels are less than 0.41 dB.

Description: For a highly efficient ON–OFF keying (OOK) transmitter, a microwatt-level ultralow-power (ULP) driver and power amplifier (PA) are designed. For efficient amplification with very high optimum impedance in the ULP application, a class-C topology is implemented and loadpull simulations are carried out to show that the proposed PA can achieve good efficiency at high optimum load impedance without any harmonic tuning. In addition, a voltage-shaping driver is optimized together with the PA for an efficient drive. The proposed driver shapes the PA input voltage into a waveform having a small conduction angle. The shaped input voltage drives the PA to a saturated operation for good efficiency even if the supply voltage is low in the drive stage. The developed driver and PA are implemented in a CMOS 65-nm process and support a 1-Mb/s OOK modulated signal. The implemented PA achieves a drain efficiency of 50.8% at the −6.8-dBm output power and 49.8% at the −10-dBm output power when transmitting continuous 1 signal.

Description: This paper introduces a one-port method for estimating model parameters of vector network analyzer calibration standards. The method involves measuring the standards through an asymmetrical passive network connected in direct mode and then in reverse mode, and using these measurements to compute the S-parameters of the network. The free parameters of the calibration standards are estimated by minimizing a figure of merit based on the expected equality of the S-parameters of the network when used in direct and reverse modes. The capabilities of the method are demonstrated through simulations, and real measurements are used to estimate the actual offset delay of a 50- ${Omega }$ calibration load that is assigned zero delay by the manufacturer. The estimated delay is 38.8 ps with a $1sigma $ uncertainty of 2.1 ps for this particular load. This result is verified through measurements of a terminated airline. The measurements agree better with theoretical models of the airline when the reference plane is calibrated using the new estimate for the load delay.

Description: This paper reports a new measurement method for wideband radiofrequency power amplifier (PA) characterization and digital predistortion. The proposed measurement procedure significantly relaxes the sampling rate requirement on the analog-to-digital converters of the feedback path. Successful PA linearizations were achieved in the presence of 20, 40, and 60-MHz LTE-A signals using a vector signal analyzer with sampling speeds equal to only 24, 40.96, and 61.44 Ms/s, respectively. Despite these very low sampling rates, a quasiperfect cancellation of the PA distortions was achieved (more than 50 dBc in terms of ACLR), in all tests, over bandwidths including up to fifth-order intermodulation distortions. Such a correction bandwidth is much wider than the observation bandwidths associated with the receiver sampling rates.

Description: This paper presents two W-band waveguide bandpass filters, one fabricated using laser micromachining and the other 3-D printing. Both filters are based on coupled resonators and are designed to have a Chebyshev response. The first filter is for laser micromachining and it is designed to have a compact structure allowing the whole filter to be made from a single metal workpiece. This eliminates the need to split the filter into several layers and therefore yields an enhanced performance in terms of low insertion loss and good durability. The second filter is produced from polymer resin using a stereolithography 3-D printing technique and the whole filter is plated with copper. To facilitate the plating process, the waveguide filter consists of slots on both the broadside and narrow side walls. Such slots also reduce the weight of the filter while still retaining the filter’s performance in terms of insertion loss. Both filters are fabricated and tested and have good agreement between measurements and simulations.

Description: The first reported full-system 60-GHz wireless power transfer (WPT) solution that can power batteryless and charge coil-free compact WPT devices is presented. The system is fabricated in a 40-nm digital CMOS process and an inexpensive packaging material. In the rectenna (RX), a grid antenna is integrated with a complementary cross-coupled oscillator-like rectifier. At a 4-cm spacing from the transmitter (TX), the RX harvests energy at a rate of 1.22 mW with a 32.8% efficiency, which is significantly higher than the prior state of the art. A novel theoretical analysis of the rectifier operation is presented that formulates all key specifications. The TX is equipped with a quad-core PA that produces a saturated output power ( $P_{mathrm{ sat}}$ ) of 24.6 dBm, which is the highest power delivery in digital CMOS at millimeter-wave bands. The TX peak power-added efficiency is 9.4%. In the TX, a $4 ,, times ,, 8$ -way differential power combining and a binary-tree architecture are implemented. The designed $2 times 2$ grid array antenna helps the TX produce 35.3-dBm peak equivalent isotropically radiated power. The results of the performance characterizations of the full-system and all individually fabricated blocks are reported. The quad-core PA supports power control and beam steering. A four-port TX antenna is designed that shows a 70° steering range in simulations.

Description: Multiterm Debye models, working well in the frequency and time domains, are established to describe the frequency-dependent behavior of complex dielectric properties of dry and wet human skin. The forearm data measured from 10 Hz to 100 GHz, accompanied by the genetic algorithm, are used to find the best multiterm Debye parameters for the models. These broadband models are very helpful and straightforward to investigate the interaction of transient signals such as Gaussian pulses with human skin as a dispersive medium in the time domain. The direct finite difference time domain formulation is used to propagate a Gaussian pulse through each of these media. According to this time domain analysis, the optimized perfectly matched layer and skin depth versus frequency are calculated for every skin model. Good agreement is observed between the calculated and measurement data of skin depths.

Description: Two 122-GHz phase-locked loops (PLLs) have been developed based on a 65-nm Si CMOS technology, and their performances are compared. For the first PLL, a voltage-controlled oscillator (VCO) with a frequency doubler embedded in the oscillator core was employed (PLL1), while the second PLL employs a push-push VCO (PLL2). The output powers of PLL1 and PLL2 were −8.6 and −21.9 dBm near 122 GHz, obtained from dc power dissipation of 82.9 and 87.7 mW, respectively. The respective locking ranges were measured to be 121.9–122.2 and 122.7–122.9 GHz for PLL1 and PLL2. The in-band phase noises were −59.2 and −60.1 dBc/Hz at 10-kHz offset, and the out-band phase noises were −102.4 and −99.5 dBc/Hz at 10-MHz offset for PLL1 and PLL2, respectively. The chip sizes were $1000 times 760 ~mu text{m}^{2}$ (PLL1) and $1300 times 840 ~mu text{m}^{2}$ (PLL2) including probing pads.

Description: In this paper, the design of pulse characteristics to achieve the desired image resolution for near-field synthetic aperture radar is presented. Gaussian and chirp pulses, which are the most commonly used pulses for ultra-wideband (UWB) radar applications, are considered in this paper. The effect of the pulse shape, bandwidth, integration angle, and signal-to-noise ratio (SNR) of the received pulse on the image resolution is comprehensively studied. To enhance the image resolution, preprocessing of the received pulses with envelope detection or match filtering are also studied. The range and cross-range resolutions achieved by Gaussian and chirp pulses with the same center frequency and bandwidth at various SNR values are compared. This paper shows that the Gaussian pulse with envelope detection provides better image resolution, whereas the chirp pulse with match filtering provides more resistance to noise. Closed-form equations and design guidelines are developed to design the input pulse characteristics to achieve the desired image resolution. The antennas’ effect on UWB pulses and the developed equation for cross-range resolution, are both validated using full-wave simulations and measurements.

Description: The methods of optimizing and designing compact circular coils for a higher quality factor ( $Q$ -factor) and effective wireless power transfer (WPT) for an application of a WPT system in the megahertz frequency range to implantable medical devices are presented. For an optimal design, the ohmic resistance and inductance of the coils, including skin and proximity effects, are calculated by applying the volume filament model (VFM). In a calculation using the VFM, a circular coil is regarded as a concentric multiloop coil, and then, the resistance and inductance of the coil are derived by calculating the voltages of each loop obtained from the VFM. According to the results, the $Q$ -factors of the coils are derived and analyzed. In addition, compact Rx and Tx coils for higher power transfer efficiency are properly designed at 6.78 MHz. For verification, theoretical calculation and analysis results are compared with the simulation and previous results. Coils properly designed are fabricated, and their resistance, inductance, $Q$ -factor, and efficiency are measured. Measurement results have good agreement with the calculation. The fabricated system is compared with the previous results designed at a lower frequency from the viewpoint of size and efficiency.

Description: Electromagnetics lay the foundation of electronic, electrical, and computer science technology. Without it, we would not have electric power, cars, radios, cellular phones, computers, and many more technologies that we take for granted; our world would be totally different and our professions in electrical and computer engineering would not exist. Human beings have long known about electromagnetism and early devices include the compass and signaling fire lights. A beautiful theory of the electromagnetic field was put forward by James Clerk Maxwell and later reformulated by Oliver Heaviside and Heinrich Hertz, all of them being among the 19th century greatest physicists and mathematicians. Today, when we deal with electromagnetic problems that embody power, radio, microwave, terahertz, and optical applications, we have to solve Maxwell’s equations, although approximate models of Maxwell’s equations, circuits and lump elements, are often used, especially at low frequencies.

Description: This paper presents the development and the validation of a scheme for modeling a lumped element in the finite-difference time-domain (FDTD) method that uses the scattered-field formulation. The proposed scheme is an adaptation of the scheme for modeling a lumped element in the FDTD method that uses the total-field formulation. The proposed scheme is presented in two different versions, one that uses a semi-implicit scheme and another one that uses a fully explicit scheme. The numerical experiments show the semi-implicit scheme to be slightly more accurate than the fully-explicit scheme, based on comparing the values of the plane-wave scattering coefficients obtained numerically with those obtained analytically. The proposed scheme is both accurate and stable in treating both dielectric and perfect electrical conductor, in the presence of a lumped source and/or an incident field.

Description: This paper describes the generalized 2.5-D finite-element method (FEM), a powerful method to analyze a class of waveguide components. The method is based on 2-D FEM in combination with a sinusoidal variation of the field in the third dimension. We discuss the application of the method to an $E$ -plane branched ortho-mode transducer, a septum polarizer, and a waffle-iron low-pass filter.

Description: We develop a new matrix-free time-domain method, which requires no matrix solution, in unstructured meshes for general 3-D electromagnetic analysis. The method handles arbitrary unstructured meshes with the same ease as a finite-element method. Meanwhile, it is free of matrix solutions manifested by a naturally diagonal mass matrix, just like a finite-difference time-domain method. Different from our previous formulation where traditional curl-conforming vector bases are employed, modified vector bases are developed in this paper to directly connect the unknown coefficients of the vector basis functions employed to represent E (or H) with the unknowns obtained from the curl of H (or E), without any need for transformation. The proposed method employs only a single mesh. It does not require any interpolation and projection to obtain one field unknown from the other. Its accuracy and stability are guaranteed theoretically. Numerous experiments on unstructured triangular prism and tetrahedral meshes, involving both homogeneous and inhomogeneous and lossy materials, demonstrate the generality, accuracy, stability, and computational efficiency of the proposed method. The modified higher order vector bases developed in this paper can also be used in any other method that employs higher order bases to obtain an explicit relationship between unknown fields and unknown coefficients of vector bases.

Description: In this paper, a nonintrusive polynomial chaos (PC) approach for the fast multidimensional uncertainty quantification of microwave/RF networks is presented. The key feature of this paper is the development of a linear regression methodology based on sparse D-optimal design of experiments to accurately evaluate the PC coefficients of the network responses. A greedy search algorithm to identify the sparse set of D-optimal design of experiments from within a multidimensional random space has been presented. Additional numerical approaches to further accelerate the search algorithm for high-dimensional random spaces have also been developed.

Description: Loewner matrix (LM) interpolation-based macromodeling methods can generate an accurate macromodel for large and complex structures. However, there is less flexibility in the choice of the macromodel order due to the need to ensure passivity. In this paper, an algorithm is proposed to obtain a reduced order model based on LM interpolation while still maintaining the passivity of the macromodel. This is achieved by first relaxing the passivity requirement during the order selection process; then a new passivity enforcement scheme with significantly improved speed and convergence properties is applied. The proposed approach results in a significantly reduced macromodel size while maintaining accuracy and passivity conditions. The efficiency of the new approach is shown in the examples.

Description: The mode-matching technique (MMT) is employed to analyze and design the transition from substrate integrated waveguides (SIWs) to substrate mounted waveguides (SMWs) that are mounted on top and/or at the bottom of the substrate. Coupling between the layers is facilitated by apertures of the thickness of the substrate’s metallization. By appropriately segmenting the transition, a simple and fast MMT routine is developed. The results obtained for a single waveguide resonator mounted on the substrate agree well with simulations in CST and HFSS and, thus, validate the MMT code. Furthermore, the routine is extended to accommodate the design of more complex structures. A five-resonator SMW filter with additional SIW resonators to add transmission zeros and a diplexer are presented and prototyped. All the measured results are in good agreement with the MMT and the CST simulation results, thus validating the design procedure.

Description: In this paper, a new concept of matrix-inversion-less derived physically expressive circuit method of model order reduction for large-scale high-speed/microwave circuit problems is proposed. It is the first model that is derived based on the mesh information of partial element equivalent circuit modeling. This new proposed method absorbs insignificant nodes and parallel branches while retaining the physical meaning of all the inductive and capacitive elements. This method does not involve any matrix inversions or decompositions and its computational overhead is dominated by outer products that can be simply accelerated by the massive GPU acceleration technique. The resultant order-reduced circuit is very useful for not only speeding up the analysis of a large-scale high-speed/microwave circuit but also interpreting the physical insight of the circuit layout from the circuit domain point of view. Three numerical examples are given, demonstrating the versatility, scalability, accuracy, and simplicity of the method.

Description: It has been observed that some surface finish like nickel–gold plating has exhibited significantly higher losses than expected on high-speed interconnects like printed circuit board (PCB) trace and packaging. The investigation has revealed that this extra loss results from the ferromagnetic characteristics of nickel material with large resistivity and nonunit frequency-dependent relative permeability. As a result, a high-speed PCB design must take into account the board surface finish effect, solder-mask coating, and the physical geometry deformation of copper related to the etching process when modeling the PCB trace, which can be accomplished by using 3-D electromagnetic field simulation tools. Simulation results are correlated with vector network analyzer (VNA) measurements on several test cases and also on the actual application boards. In our experimental studies on PCB test structures with electroless nickel/immersion-gold (ENIG) and electroplated nickel–gold plating, there is no observation of resonating anomalies in the insertion loss and group delay related to nickel permeability. Both simulation and measurement results have demonstrated that PCB board with ENIG and solder mask over bare copper finish has less signal loss than that with ENIG or hard-gold finish.

Description: In this paper, the use of a reference rotating around the axis of magnetization, with the resonance frequency $gamma {H} _{0}$ ( $gamma $ is the gyromagnetic ratio and ${H} _{0}$ is the applied magnetic field), allows reducing the number of equations and fields needed for the time-domain analysis of magnetized ferrites compared with the usual case, where a fixed reference is used. The finite-difference time-domain method is used to implement the obtained equations for the analysis of some guiding structures. Numerical results show good agreement with those obtained using the equations of the fixed reference, with an improvement in the efficiency of the simulation.

Description: In the traditional microwave heating partial differential equation (PDE) model, one of the main characteristics is the infinite-dimensional nature, which does not allow to readily design and implement a controller. Motivated by this obstruction, this paper proposes a microwave heating finite-dimensional ordinary differential equation (ODE) model, which can not only describe the thermodynamics field with nonhomogeneous boundary conditions but also be coupled with the variation of electromagnetic field in temperature-dependent dielectric media. Initially, the equivalent PDE model with a homogeneous boundary condition is derived by constructing an auxiliary function in order to directly derive the eigenspectrum of the spatial differential operator. With the help of model-reduction techniques, the dominant dynamics of temperature distribution are subsequently captured with a reasonable Galerkin truncation. The simulation results on microwave heating a water prototype show that the temporal and the spatial evolution of the temperature profile can be described by solving the temperature-dependent electromagnetic field and the finite-dimensional ODE model. Moreover, the effectiveness of the model is verified by comparing with the numerical results from the traditional COMSOL model. A further development of this ODE model may provide a useful numerical tool for the design and synthesis of microwave heaters to avoid thermal runaway phenomena.

Description: A novel microwave imaging approach to reconstruct the dielectric properties of targets hosted in partially known, noncanonical, scenarios is proposed and assessed. The method takes joint advantage of the recently introduced virtual experiments paradigm and exploits a new linear approximation developed within such a framework. Such an approximation implicitly depends on the unknown targets and, therefore, has a broader applicability as compared with the traditional distorted Born approximation. Being noniterative, the resulting distorted-wave inversion method is capable of quasi-real-time imaging and successfully images nonweak perturbations. The performances of the novel imaging method have been assessed with simulated data and validated experimentally against some of Fresnel data sets.

Description: In this paper, a methodology for fast multiobjective optimization of the miniaturized microwave passives has been presented. Our approach is applicable to circuits that can be decomposed into individual cells [e.g., compact microstrip resonant cells (CMRCs)]. The structures are individually modeled using their corresponding equivalent circuits and aligned with their accurate, EM simulated representations, by means of implicit space mapping (ISM). The ISM-corrected cells are then assembled into the entire structures and their Pareto-optimal solutions (here, representing the best possible tradeoffs between the structure size and electrical performance) are obtained using evolutionary methods. The refinement is then carried out for the selected structure realizations using, again, SM. The latter stage is necessary, because the cell-based equivalent circuit models do not account for EM cross-couplings between the cells. The proposed methodology allows for rapid identification of compromise geometries concerning size-performance tradeoffs and, more importantly, permits quality comparison of particular CMRC realizations from the point of view of their suitability for a given compact circuit implementation. Our approach is demonstrated using several variations of the three-section wideband impedance matching transformers consisting of two types of CMRC structures. Numerical validation of the results is provided.

Description: Due to manufacturing requirements, surface finishes have become a necessity in printed circuit board design. These finishes have significant effects on the RF performance of the transmission lines. In this paper, a filament modeling approach is used to model skin, proximity, and surface roughness effects in transmission lines with surface finishes up to 70 GHz. The approach shows a high accuracy compared with measurements. The model also gives an insight into how the current distributes itself by showing the frequency dependent proportion of the current that flows in each surface finish layer. In the case of NiP–Au or Ni–Au surface finishes, current migrates increasingly into gold at high frequencies and reaches a maximum in the Ni or NiP at around 3.5 GHz, and then declines. The distribution of the current in different materials can also be explained as the decay of an electromagnetic wave at the surface of the conductor. This approach shows that the evanescent wave in the cross section of the conductor can be analyzed as analog to a transmission–reflection problem, what we will call the surface finish effect. This effect brings into question the accuracy of the traditional skin-depth value, $delta $ , and the models that depend on it, such as most surface roughness correction factors, for structures where different metals are layered in thicknesses that are not much larger than $delta $ .

Description: In this paper, a new qualitative inverse scattering method for microwave imaging is proposed. The presented method is inspired by the previously introduced orthogonality sampling method (OSM) and direct sampling method (DSM), which aim to recover the reduced scattered fields . Both the OSM and the DSM are classified as backpropagation-based methods, and they are linked with the point source method and the linear sampling method. Although 3-D formulations of the OSM and the DSM exist for electromagnetic inverse scattering problems, the extension of these methods to near-field measurements is an open problem. The main contribution of this paper is introducing two novel linear operators to connect the reduced scattered fields and the tangential component of the scattered electric field measured on a circle for 2-D transverse electric (2-D-TE) and transverse magnetic (2-D-TM) inverse problems with the near-field measurements. To derive the kernel of these linear transformations, an integral equation is defined for each of the 2-D-TM and 2-D-TE problems. These equations are analytically solved, and the solutions are shown to be computable without any regularization. In addition to these theoretical contributions, the accuracy of the proposed approaches is shown with both numerical and experimental data. The constraints of the method are the measurement circle has to encover the scatterers and the targets have to be bounded in size and weak in contrast. The obtained results show that the developed approaches can be very useful in real-world applications, such as nondestructive testing and biomedical imaging.

Description: This paper presents a systematic investigation of quarter-mode filters in substrate integrated waveguide (SIW) technology. This class of filters is particularly convenient because it combines the features of SIW structures with the improvement of size reduction. After a thorough analysis of the quarter-mode SIW cavity, this paper presents different coupling mechanisms and feeding techniques for the design of quarter-mode SIW filters: side coupling and corner coupling are considered, highlighting the advantages and disadvantages of the two techniques. Novel filter topologies are introduced, with the design and experimental verification of simple filters and their extension to higher order filter structures. Techniques to introduce transmission zeros are described and demonstrated. Moreover, the combination of quarter-mode SIW cavities and coplanar waveguide resonators leads to increasing the filter order to higher order and allows the implementation of quasi-elliptic filters.

Description: A design approach for substrate-integrated waveguide (SIW) to rectangular waveguide (RWG) transitions based on the synthesis of antipodal finline tapers is proposed. The taper is designed using a reflection-based impedance definition as no suitable model is available for antipodal finlines. The characteristics of the finline are determined from full-wave simulation. To demonstrate the proposed method, two SIW-to-RWG transitions are designed and characterized at the $K$ -band. The measured back-to-back transitions exhibit a return loss above 15 dB and an insertion loss below 1 dB between 16.7 and 20.5 GHz and between 21.1 and more than 31 GHz, respectively. A good agreement between the synthesis model and full-wave simulation of the taper on one hand and between simulation and measurements of back-to-back transitions on the other hand is demonstrated.

Description: This paper presents novel ultracompact waveguide bandpass filters that exhibit pseudoelliptic responses with the ability to place transmission zeros on both sides of the passband to form sharp rolloffs. The filters contain $E$ -plane extracted pole sections (EPSs) cascaded with cross-coupled filtering blocks. Compactness is achieved by the use of evanescent mode sections and closer arranged resonators modified to shrink in size. The filters containing nonresonating nodes are designed by means of the generalized coupling coefficients’ extraction procedure for the cross-coupled filtering blocks and EPSs. We illustrate the performance of the proposed structures through the design examples of third- and fourth-order filters with center frequencies of 9.2 and 10 GHz, respectively. The sizes of the proposed structures suitable for fabricating using the low-cost ${E}$ -plane waveguide technology are 38% smaller than ones of the ${E}$ -plane extracted pole filter of the same order.

Description: A design and analysis approach that enables extracting the full filtering potential of triple-mode filters while greatly simplifying the construction and hence reducing the filter cost is presented. The presented way views multimode resonators of cavity filters as resonators coupled in parallel, with every mode within the structure completely orthogonal; hence, there are no interresonator couplings. Each resonator then independently sees the interfacing input and output while the strength and phase of the coupling, along with the resonator frequencies, dictate the transmission zero placement. Thus, a completely general frequency response can be attained with as many arbitrarily placed zeros as there are multimode resonators. The absence of intracavity couplings allows using a simple rectangular cuboid while the input-to-output coupling via a single printed circuit board interface manages three controllable transmission zeros per cuboid. To verify the proposed approach, multiple designs operating at the DCS-1800 Band-3 are presented.

Description: A complete solution from parameter extraction to large-signal electrothermal model generation for gallium nitride (GaN) HEMTs is presented in this paper with the consideration of trapping deduced gate and drain lag effects. The extrinsic parasitic parameters are extracted by multibias hot-FET optimization using artificial bee colony algorithm. New terminal charge ( $Q_{mathrm {gs}}$ , $Q_{mathrm {gd}}$ , and $Q_{mathrm {ds}})$ models with temperature dependence are proposed to better characterize the GaN devices. Physical mechanisms of the electrothermal and trapping effects have been investigated, and the artificial neural network (ANN) is exploited to construct the drain current based on pulsed $I$ – $V$ (PIV) measurements. Besides the instantaneous terminal voltages, additional three auxiliary variables are employed to describe the memory effects of GaN HEMT: channel temperature, gate trapping state, and drain trapping state. These variables are identified from PIVs to compose the input layer of the ANN, while in the simulator, they are captured by the thermal and two envelop tracking subcircuits. These physical auxiliary variables together with the ANN technology enable unlimited fitting sets of PIVs with satisfying accuracy. Single-tone and two-tone on-wafer measurements are conducted for the verification, and a good agreement has been achieved between the measurements and simulations.

Description: A new reconfigurable bandstop filter class is proposed, which has the unique property of possessing multiple insertion loss states with a common group delay state. These filters switch between a low-insertion-loss allpass state and a high-rejection bandstop state. The theory, synthesis, and design of these filters are presented. As a demonstration of the concept, a fourth-order constant-group-delay switched bandstop filter microstrip prototype was designed, built, and tested. The prototype has a measured bandstop-state center frequency of 1000 MHz, a 3-dB bandwidth of 119.15 MHz, a stopband rejection of 32.52 dB, a maximum allpass-state insertion loss of 4.08 dB, and a negligible group delay variation between the two states.

Description: We present an unconditionally stable weighted Laguerre polynomials (WLPs)-based finite-difference time-domain (FDTD) algorithm for modeling wave propagation in isotropic cold plasma. The plasma effects contributed by electrons and collisions are modeled by current density vectors collocated with the electric field components. The factorization-splitting scheme is employed to translate the large sparse matrix equation in the conventional WLP-FDTD algorithm into two and six tri-diagonal ones for 2-D and 3-D problems, respectively. This procedure significantly improves the efficiency of the WLP-FDTD algorithm in terms of computational expenses. The stretched-coordinate perfectly matched layer with a complex-frequency-shifted factor is implemented as the absorbing boundary condition. The accuracy and efficiency of the proposed algorithm are validated by numerical examples.

Description: To simulate lumped elements (LEs) more accurately in metamaterial absorber (MA) designs, a finite-volume LE (FVLE) model based on the time-domain finite-integral theorem (TDFIT) is proposed in this paper. In MA designs, lumped resistors and capacitors play an important role in dissipating electromagnetic (EM) fields, controlling resonant frequencies, and achieving an impedance matching. Through a rigorous mathematical derivation, we successfully prove that an arbitrary lumped resistor or capacitor can be modeled more accurately by modifying the conductivity or permittivity of a finite-volume model in TDFIT method. Compared with existing traditional zero-volume LE (ZVLE) solutions, the coupling effect between the circuit part and the EM part can be considered much better in the proposed FVLE model. For this reason, the numerical results of the FVLE model match the measured results much better. In addition, a result comparison is given to validate that the challenges of grid dispersion error and frequency response error in the classic ZVLE solution can be greatly overcome by the proposed FVLE model.

Description: Integrated antennas have become the attractive solution as the electromagnetic (EM) interface for mm-Wave and terahertz ICs. However, on-chip antennas lying at the interface between two different dielectrics (such as air and substrate) can channel most of its power into multiple nonradiative surface-wave modes, reducing efficiency drastically. In this paper, we consider the following problem: given a dielectric substrate, what is the theoretical optimal 2-D surface-current configuration that collectively suppresses surface waves and maximizes radiation efficiency with the desirable radiation pattern? This paper also discusses demonstrative examples of a circuit-EM codesign approach to realize the approximation of such current configurations. Measurement results of radiating arrays in CMOS at mm-Wave frequencies (250–300 GHz) are presented and compared with theoretical predictions.

Description: In this paper, a class of balanced wideband and dual-band bandpass filters (BPFs) is proposed and designed on a hybrid multimode resonator. This resonator is composed of two distinctive kinds of transmission lines, i.e., microstrip line and slotline, so it is called a hybrid resonator. On one hand, the resonator itself has the common-mode (CM) rejection as an inherent property by virtue of the hybrid structure; on the other hand, the microstrip/slotline transitions for feeding are avoided because normal microstrip feeding schemes are valid via microstrip lines inside this resonator. As such, the proposed hybrid resonator is largely different from those in the existing balanced BPFs with intrinsic CM rejection. In the traditional one, the resonator is formed by a slotline and it is connected with microstrip/slotline transitions for differential-mode (DM) transmission and CM rejection. What is more valuable, the hybrid resonator can be easily constructed by replacing a portion of then microstrip line in the traditional microstrip resonator with the slotline. Thus, the diversity of the balanced wideband BPFs with intrinsic CM rejection can be extremely enhanced and the balanced dual-mode dual-band BPF can be successfully designed. Two different balanced BPFs under wideband and dual-band operations are finally designed and fabricated to support our theory.

Description: This paper proposes a novel concept of an integrated duplex antenna for realizing a compact multifunction RF front end by integrating a duplexer and a dual-band patch antenna. First, an all-resonator-based duplexer is designed. It is composed of two sets of split-ring resonators as channel filters, which are joined by a dual-mode stub-loaded resonator as the junction resonator. Then, a novel dual-band patch antenna is achieved by coupling a patch with a hairpin resonator through a slot in the ground. Uniform radiation characteristics have been achieved across the two bands. Finally, the duplexer is integrated with the dual-band patch antenna to form a highly integrated duplex antenna by coupling the hairpin resonator to the junction resonator of the duplexer directly. In this process, the 50- $Omega $ interface and matching network between them are removed, contributing to a compact footprint. The details of codesign approach have been discussed in this paper. Compared with the traditional cascaded duplexer and antennas, this paper is much more compact and integrated but with an improved frequency response. A prototype of an integrated duplex antenna at S-band is fabricated and measured, showing two operation channels of 2.52–2.65 GHz for transmitting and 2.82–2.94 GHz for receiving with an isolation of over 32 dB. The measured results agree well with the simulation results.

Description: This paper presents a high-efficiency gallium nitride Doherty power amplifier (DPA) using an integrated compensating reactance (CR) for broadband operation. With an additional quarter-wavelength transmission line integrated in the peaking amplifier output, a CR is generated to compensate the load impedance of the carrier amplifier in the low-power region and thus enhance the back-off efficiency over a wide frequency range without affecting the Doherty load modulation at saturation. For this purpose, a peaking output matching network (OMN) is employed to convert the output impedance of the peaking device into quasi-short circuit when it is off and achieve proper impedance matching when it is on. A two-point matching technique using the transmission ( $ABCD$ ) matrix is employed to design such desired OMN. Measurement results show that the DPA has a 6-dB back-off efficiency of 50%–55% and a saturated efficiency of 57%–71% over the frequency band of 1.7–2.8 GHz (49% fractional bandwidth). When driven by a 20-MHz long term evolution modulated signal at 6.5-dB back-off power, the DPA can achieve an average efficiency of more than 50% with high linearity after linearization over the design frequency band.

Description: Design and implementation of high-efficiency microwave and mm-wave CMOS silicon-on-insulator (SOI) power amplifiers (PAs) based on a stacked cell approach is presented. Two stacked cell PAs have been implemented in GlobalFoundries 45-nm CMOS SOI technology. The first PA operating at K-band (24–28 GHz) is designed with three stacked triple Cascode cells. Each cell uses three standard transistors with separate layout. At 24 GHz, the K-band PA biased under a supply voltage of 10.8 V measures a maximum linear power gain of 13 dB, a saturated output power $P _{mathrm {SAT}}$ of 25.3 dBm, a −1-dB output power $P _{1mathrm {dB}}$ of 23.8 dBm, and a peak power-added efficiency (PAE) of 20%. The second PA targeted at U-band frequencies is designed with two stacked triple Cascode cells. Transistors in each cell have a combined layout that reduces parasitic capacitances, leading to significant improvement in the PAE at mm-wave frequencies. The U-band PA operates from 42 to 54 GHz. At 46 GHz, and under a supply voltage of 6 V, it measures a saturated output power ( $P _{mathrm {SAT}}$ ) of 22.4 dBm, a linear gain of 17.4 dB, and an unprecedented peak PAE of 42%.

Description: This paper presents a fully integrated 16-way power-combining amplifier for 67–92-GHz applications in an advanced 90-nm silicon germanium HBT technology. The 16-way amplifier is implemented using three-stage common-emitter single-ended power amplifiers (PAs) as building blocks, and reactive $lambda $ /4 impedance transformation networks are used for power combining. The three-stage single PA breakout has a small-signal gain of 22 dB at 74 GHz, and saturation output power ( $P_{mathrm{ sat}}$ ) of 14.3–16.4 dBm at 68–99 GHz. The power-combining PA achieves a small-signal gain of 19.3 dB at 74 GHz, and $P_{mathrm{ sat}}$ of 25.3–27.3 dBm at 68–88 GHz with a maximum power added efficiency of 12.4%. The 16-way amplifier occupies 6.48 mm 2 (including pads) and consumes a maximum current of 2.1 A from a 1.8 V supply. To the best of our knowledge, this is the highest power silicon-based $E$ -band amplifier to date.

Description: In this paper, a miniaturized evanescent mode waveguide filter using rectangular ring resonators (RRRs) is presented. The evanescent mode waveguide resonator cell (EWRC), composed of a section of evanescent mode waveguide loaded with a pair of RRRs, is designed and analyzed. Quality factors of the EWRC are simulated and calculated. The resonant mechanism and the values of the equivalent lumped elements of EWRCs are given for further design and application of this kind of filter. A miniaturized waveguide filter is designed and fabricated to operate at Ka -band, using the ${W}$ -band standard waveguide (WR-10) with a cross-sectional size of $2.54~text {mm} times 1.27$ mm. The proposed filter can realize a large size reduction compared with the conventional waveguide filter, especially leading to a cross-sectional size reduction of 87.2%. Despite a slight frequency shift, good agreement has been achieved between the simulation and measurement results. The proposed filter has large out-of-band rejection, wide stopband, and high selectivity. In addition, a compact diplexer with high isolation is presented.

Description: A dual-loop feedback broadband low-noise amplifier (LNA) employing second-order inter-modulation distortion (IMD2) cancellation is implemented in an 0.18- $mu {text {m}}$ silicon-on-insulator (SOI) CMOS technology. The dual-loop feedback configuration stabilizes an input return loss ( $S _{11}$ ) of the LNA at the VHF low band around 50 MHz with small dc blocking capacitors. In order to achieve a second-order output-referred intercept point (OIP2) of greater than +50 dBm with reasonably low power consumption, all of the building blocks of the proposed LNA are designed to have a complementary configuration while the body-bias control technique is applied to the inverter-based resistive feedback amplifier. In addition, the peaking inductor is placed inside the feedback loop at the gate of the input transistor to enhance the bandwidth of the LNA. The designed LNA achieves a measured power gain ( $S _{21}$ ) of 10.1 dB, a noise figure (NF) of less than 4 dB, and an input return loss ( $S _{11}$ ) of greater than 10 dB over frequencies ranging from 50 MHz to 3 GHz. The measurements show a third-order output-referred intercept point (OIP3) of +17.8 dBm and an OIP2 of +53 dBm at 1 GHz.

Description: A systematic design procedure for highly linear and reliable amplifiers is proposed. The procedure deals with nonlinear modeling, junction temperature prediction methods, and circuit design techniques. A wideband linear monolithic microwave integrated circuit power amplifier based on a space-qualified GaAs process for $C$ -band and extended $C$ -band multicarrier satellite transponder is reported and described. The amplifier uses a bus-bar combiner in the power stage reaching an output power of 26.7 dBm at 1-dB compression point, with a small signal gain above 25 dB in the operation band between 3 and 6 GHz. The output third-order intercept point reaches levels above 40 dBm. The design ensures high reliability keeping the junction temperature below 112 °C.

Description: This paper presents the implementation of a broadband quasi-circulator through a cascading distributed balun using a 90-nm CMOS process. The isolation, $vert text{S}31vert $ , of the proposed three-port quasi-circulator can be acquired through the phase cancelation technique, by connecting an additional distributed amplifier in parallel between ports 1 and 3. The thorough analysis based on an eight-port chain matrix and scattering matrix is presented for refining the circuit parameters in the initial design. Measured results show that the proposed quasi-circulator attains a broad operation bandwidth ranging from 10 to 67 GHz. Moreover, the quasi-circulator also has good insertion gain of 0.5 to 4.8 dB, as well as isolation $vert text{S}31vert $ , which is better than 23 dB. Consequently, the proposed quasi-circulator delivers wide bandwidth performance, good port-to-port isolations, good insertion gain, and high linearity based on the cascading distributed balun with phase cancelation technique.

Description: This paper presents an integrated four-way power-combining multiplier for 200–230-GHz applications in an advanced 90-nm silicon germanium HBT technology. The active multiplier is implemented using balanced transistor pairs driven by pseudodifferential power amplifiers (PAs) at 100–120 GHz and the outputs at 200–240 GHz are power combined using reactive $lambda $ /4 impedance transformation networks. A single multiplier breakout results in an output power of 1.8 dBm at 245 GHz with a peak conversion gain of −15.5 dB. The power-combining multiplier achieves an output power of 8 dBm at 215 GHz and >5 dBm at 200–230 GHz. A peak conversion gain of 1.6 dB is achieved at an output power of $sim 0$ dBm at 215 GHz. The four-way combined multiplier occupies 3.63 mm 2 , including pads, and consumes 1.2 A from a 1.8 V supply mainly due to the differential 100–120-GHz PAs. To the best of our knowledge, this is the highest output power achieved in multipliers and amplifiers among all silicon-based technology to-date at frequencies above 200 GHz and with a record wide bandwidth.

Description: A CMOS vector-sum phase shifter covering the full 360° range is presented in this paper. Broadband operational transconductance amplifiers with variable transconductance provide coarse scaling of the quadrature vector amplitudes. Fine scaling of the amplitudes is accomplished using a passive resistive network. Expressions are derived to predict the maximum bit resolution of the phase shifter from the scaling factor of the coarse and fine vector-scaling stages. The phase shifter was designed and fabricated using the standard 130-nm CMOS process and was tested on-wafer over the frequency range of 4.9–5.9 GHz. The phase shifter delivers root mean square (rms) phase and amplitude errors of 1.25° and 0.7 dB, respectively, at the midband frequency of 5.4 GHz. The input and output return losses are both below 17 dB over the band, and the insertion loss is better than 4 dB over the band. The circuit uses an area of 0.303 mm 2 excluding bonding pads and draws 28 mW from a 1.2 V supply.

Description: There are many techniques that have been developed to reduce peak to average power ratio (PAPR) in communication systems, but very few that can be implemented without any increase in the hardware complexity of a given system. This paper presents a method of PAPR that does not require any increase in hardware complexity as it achieves its effect through modification of the already existing transmit and receive pulse shaping filters. Furthermore, this paper presents the effect that this PAPR method has on the communications system as a whole by presenting the results on linear power increase and channel capacity with and without the PAPR method.

Description: This paper presents new circuit topologies and design techniques for low-phase-noise (PN) complementary metal–oxide–semiconductor (CMOS) millimeter-wave quadrature voltage-controlled oscillator (QVCO) and VCOs. A transformer-coupled QVCO topology with extra phase shift is proposed to replace the coupling transistors, which eliminates coupling transistors’ noise, decouples the tradeoff between PN and phase error, and improves the PN performance. This technique is demonstrated in a millimeter-wave QVCO with a measured PN of −119.2 dBc/Hz at 10-MHz offset of a 56.2-GHz carrier and a tuning range of 9.1%. In addition, an inductive-divider-feedback technique is proposed in an $LC$ VCO design to improve the transconductance linearity, resulting in a larger signal swing and lower PN compared with the conventional $LC$ VCOs. The effectiveness of this approach is demonstrated in a 76- and a 90-GHz VCO design, both fabricated in a 65-nm CMOS process, with an FOM $_{{mathrm {T}}}$ of 173.6 and 173.1 dBc/Hz, respectively.

Description: Estimating the amount of harvestable ambient RF and microwave power from the omnipresent electromagnetic sources is of vital importance when designing a wireless device that makes use of ambient microwave power harvesting (AMPH) as a power source. This paper studies and looks into the underlying RF and microwave rectification mechanism at low input ambient power levels, specifically −30 dBm and below. A fundamental theory is formulated and developed, which is able to correctly predict the efficiency of a rectifier including the effects of matching network insertion losses through an easy-to-understand analytical model. The suggested model provides a direct design guideline in determining and choosing the optimal diode for a predetermined application. Based on the developed theoretical framework, the diode characteristics that have a direct impact on the microwave power conversion efficiency are discussed in detail. Three different Schottky diode rectifiers were designed on the basis of the tools described in this paper, thereby validating the proposed model and highlighting the influence of critical diode parameters on its performances. The measured results are then compared with those predicted by the proposed model and state-of-the-art microwave power rectifiers, showing a good model accuracy and also a 10% improvement in the rectifying efficiency for the low input power levels of interest.

Description: This paper presents a very low noise suspended micro-bolometer with an in-situ vacuum micro-package so as to prevent thermal loss to the surrounding area and minimize the thermal conductivity of the ambient. Bolometer thermal models with respect to vacuum pressure are developed and verified by finite-element method (FEM) simulations. It is found that with the vacuum micro-package, a micro-scale (and not a nano-scale) size bolometer can achieve a noise equivalent power (NEP) close to the theoretical limit. Vacuum packaged Ni micro-bolometers with a sheet resistance of 6.2– $6.5~Omega /{text {sq}}$ , widths of 1.3 and $2.3~ mu {text {m}}$ , and a micro-vacuum ambient of 1 torr are fabricated using advanced micro-machining techniques. The measured responsivity (RESP) of a room-temperature micro-bolometer with $w _{b} =1.3~ mu {text {m}}$ is 922 V/W ( $beta =1.54~{ text {M}}Omega /{text {W}}$ ) for $R _{b} =275 ~Omega $ and $I _{b} =0.6 ~{text {mA}}$ . The measured best NEP is 7.2 pW/Hz 0.5 at 3-kHz modulation frequency for $w _{b} =1.3~ mu {text {m}}$ , $l _{b} =40 ~mu {text {m}}$ , and $R _{b} =230~ Omega $ , and is the first demonstration resulting in <10 pW/Hz 0.5 performance among uncooled micro-bolometers without any nano-patterning methods. The application are- s are in low-cost THz imaging systems and wideband THz detectors.

Description: This paper presents a dual-mode intermediate frequency (IF) signal processing circuit for pulse compression radar (PCR) and symbol recovery. A half-duplex architecture is proposed to support modulation and demodulation of PCR signals. For data communication, the modulator and the demodulator support up to 3-Gb/s QPSK signal. For range sensing, the proposed IF correlation technique supports 1.5-GHz bandwidth (BW) and 3/5/7-b Barker codes for 10-cm range resolution. The circuit includes a high-linearity switch, a modulator, a reconfigurable demodulator/correlator, and an in-phase and quadrature clock signal generator. This proposed system is fabricated with 90-nm CMOS, and each channel can be configured to operate from 200 Mb/s to 1.5 Gb/s with different Barker codes. The maximum power consumption is 54 mW with 1.5-GHz BW (10 cm) in range sensing mode and 49 mW at a rate of 3 Gb/s in data communication mode.

Description: Magnetic nanoparticle (MNP)-assisted microwave hyperthermia using an active integrated heat applicator is presented in this paper. The effect of MNPs on microwave hyperthermia has been analyzed by coupled electromagnetic–thermal analysis considering the frequency- and temperature-dependent properties of biological tissues. For enhanced heating efficiency and material sensitivity, the optimum microwave frequency for hyperthermia has been identified using the presented analysis and confirmed with experiments. In order to demonstrate MNP-assisted hyperthermia, an active integrated applicator is developed. A microwave signal generation module, which has a voltage-controlled oscillator and a power amplifier, has been fabricated in monolithic microwave integrated circuits and integrated on the microwave heat applicator based on a spiral radiator. A dual-channel logarithmic power detector and a directional coupler have been also employed to monitor power levels during hyperthermia, which allows understanding of the heating mechanism. In vitro heating experiments on phantoms, pork muscles, and tumors with and without MNPs show a large difference in temperature rises, which demonstrates the effectiveness of MNPs for low-power and material-specific hyperthermia. Combined with MNP targeting on the cancer cells, MNP-assisted microwave hyperthermia can be a promising method for a low-power and cancer-specific treatment with minimal collateral damage.

Description: A new optical technique for suppression of electronic interference is detailed theoretically and experimentally. The method is based on operating an angle-modulated photonic link in its nonlinear regime, where Bessel functions govern the response. This novel signal-processing technique is analyzed for optical intensity and phase modulation. Experimental results demonstrate suppression of continuous-wave, pulsed, and chirped signals at levels ranging from at least 30 dB to upwards of 70 dB relative to small-signal conditions.