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Beschreibung: This installment of Computer's series highlighting the work published in IEEE Computer Society journals comes from IEEE Transactions on Visualization and Computer Graphics. The Web extra at http://youtu.be/E1PVTitj7h0 is a video demonstration of a novel solution to multivariate data visualization that helps users interactively explore data by combining standard presentations, from detailed views to high-level overviews.

Beschreibung: The data rearrangement engine (DRE) performs in-memory data restructuring to accelerate irregular, data-intensive applications. An emulation on a field-programmable gate array shows how the DRE could improve speedup, memory bandwidth, and energy consumption on three representative benchmarks.

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Beschreibung: The major activity during speech production is glottal activity and is earlier detected using strength of excitation (SoE). This work uses the normalized autocorrelation peak strength (NAPS) and higher order statistics (HOS) as additional features for detecting glottal activity. The three features, namely, SoE, NAPS, and HOS, are, respectively indicators of different attributes of glottal activity, namely, energy, periodicity, and asymmetrical nature of the resulting source signal. The effectiveness of these features is analyzed using the differential electroglottograph signal, zero-frequency filtered signal, and integrated linear prediction residual, as representatives of source signal. The combination of glottal activity information from the three features outperforms any single of them, demonstrating different information represented by each of these features.

Beschreibung: This letter addresses the texture classification problem through a pixel-based local binary pattern (LBP) statistics aggregation mechanism. Real-world texture images often present challenges for classification algorithms in terms of intra-class variability due, among others, to variable illumination. The LBP operator, a state-of-the-art texture descriptor, possesses key properties for tackling real-world texture images: discriminative power and invariance against monotonic gray level changes. We propose a novel texture classification approach that increases the robustness of LBP-based methods with respect to any type of intra-class variations. The method locally characterizes each pixel with an LBP code histogram and globally computes the label of a textured image by aggregating pixel labels through a voting process. Our approach can be in principle applied to any LBP version, as it focuses on how statistics are computed from LBP codes. We show that the proposed pixel-based approach improves upon traditional LBP block-based approaches in terms of classification accuracy by up to 5.1 p.p. on the public Outex database for the classic LBP with various neighborhoods as well as for various LBP extensions.

Beschreibung: We present a new trigonometric basis function that is capable of perfectly reproducing circles, spheres and ellipsoids while at the same time being interpolatory. Such basis functions have the advantage that they allow to construct shapes through a sequence of control points that lie on their contour (2-D) or surface (3-D) which facilitates user-interaction, especially in 3-D. Our piecewise exponential basis function has finite support, which enables local control for shape modification. We derive and prove all the necessary properties of the kernel to represent shapes that can be smoothly deformed and show how idealized shapes such as ellipses and spheres can be constructed.

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Beschreibung: 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.

Beschreibung: The directivity factor (DF) of a beamformer describes its spatial selectivity and ability to suppress diffuse noise which arrives from all directions. For a given array constellation, it is possible to select beamforming weights which maximize the DF for a particular look-direction, while enforcing nulls for a set of undesired directions. In general, the resulting DF is dependent upon the specific look- and null directions. Using the same array, one may apply a different set of weights designed for any other feasible set of look- and null directions. In this contribution, we show that when the optimal DF is averaged over all look directions, the result equals the number of sensors minus the number of null constraints. This result holds regardless of the positions and spatial responses of the individual sensors and regardless of the null directions. The result generalizes to more complex wave-propagation domains (e.g., reverberation).

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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 $5f_{0}$ .

Beschreibung: 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.

Beschreibung: 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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Beschreibung: License plate recognition is a computer vision method that identifies vehicles from their license plates. The most crucial step of such a system is accurate localization of the plate. The authors propose a system for automatic recognition that has three phases: image capture, plate localization, and license plate number recognition. They tested their methodology on 40 different car models with different types of license plates.

Beschreibung: We consider the problem of angle-robust joint transmit waveform and receive filter design for colocated multiple-input multiple-output (MIMO) radar, in the presence of signal-dependent interferences. The design problem is cast as a max-min optimization problem to maximize the worst-case output signal-to-interference-plus-noise-ratio (SINR) with respect to the unknown angle of the target of interest. Based on rank-one relaxation and semi-definite programming (SDP) representation of a nonnegative trigonometric polynomial, a cyclic optimization algorithm is proposed to tackle this problem. The effectiveness of the proposed method is illustrated via numerical examples.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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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Beschreibung: 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.

Beschreibung: An Empirical Bayes formalization of the regularized covariance estimation problem is proposed for (possibly high-dimensional, low-sample) normal variates. A simple iteration is provided to automatically adjust the shrinkage level, which provably converges to the maximum likelihood hyperparameter estimation for any choice of the starting point. The proposed approach is effective and can outperform both MSE-optimized diagonal loading and the Rao–Blackwell Leidot–Wolf estimator in terms of covariance-matrix-specific metrics.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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 ${hbox{10}}^{-7}$ .

Beschreibung: 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.

Beschreibung: Differential spatial modulation (DSM) is a newly-emerging differential scheme tailored to the spatial modulation technique, which selects only one among a group of antennas for transmission at any time instant. DSM, however, gives rise to prohibitive search complexity when the number of transmit antennas is large. In this letter, a low-complexity suboptimal detector is proposed for DSM. It is designed based on the maximum-likelihood criterion but takes more candidates for the antenna activation orders into account. The detection is performed in two steps: the first step is to confine the number of candidates for the modulated symbols to a small portion by exploiting the symmetry of the signal constellation; the second step is to select the most likely modulated symbols from the output of the first step according to the determined antenna activation order via a Viterbi-like algorithm. Analyses and simulations show that the proposed detector achieves near-optimal performance yet largely reduces the search complexity.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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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Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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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Beschreibung: Nonlocal means is one of the well known and mostly used image denoising methods. The conventional nonlocal means approach uses weighted version of all patches in a search neighbourhood to denoise the center patch. However, this search neighbourhood can include some dissimilar patches. In this letter, we propose a pre-processing hard thresholding algorithm that eliminates those dissimilar patches. Consequently, the method improves the performance of nonlocal means. The threshold is calculated based on the distribution of distances of noisy similar patches. The method denoted by Similarity Validation Based Nonlocal Means (NLM-SVB) shows improvement in terms of PSNR and SSIM of the retrieved image in comparison with nonlocal means and some recent variations of nonlocal means.

Beschreibung: A proposed property-aware name service simultaneously supports what, where, and when properties of each IoT object through unique, text-based, and human-readable identity assignments.

Beschreibung: Since its inception, the Internet has been a complex landscape for developers as well as users to negotiate. The new ISO/IEC/IEEE 23026 standard seeks to improve websites' usability and information content and simplify Web service management and maintenance activities.

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Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: IEEE president-elect candidates address Computer Society concerns.

Beschreibung: Events of interest to Computer Society members.

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Beschreibung: Although you can't see something that isn't there, you can perceive the powerful effects of its nonexistence. The Web extra at http://youtu.be/vahyX-lM9AI is an audio recording of author David Alan Grier expanding on his Errant Hashtag column, in which he talks about the lack of connection that can exist between two people or organizations.

Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: For a proper choice of the analysis window, a short-time Fourier transform is known to be completely characterized by its zeros, which coincide with those of the associated spectrogram. A simplified representation of the time-frequency structure of a signal can therefore be given by the Delaunay triangulation attached to spectrogram zeros. In the case of multicomponent nonstationary signals embedded in white Gaussian noise, it turns out that each time–frequency domain attached to a given component can be viewed as the union of adjacent Delaunay triangles whose edge length is an outlier as compared to the distribution in noise-only regions. Identifying such domains offers a new way of disentangling the different components in the time–frequency plane, as well as of reconstructing the corresponding waveforms.

Beschreibung: In this letter, we propose HOG-Dot, a method for the direct computation of the polar image gradients coordinates from the pixels values. The proposed algorithm, to be used as the first step of the Histogram of Oriented Gradient (HOG) pipeline, approximates the exact gradient with its projection onto a versor chosen among the projection plane set. Instead of non linear computations, the HOG-Dot method exploits linear operations while introducing a bounded approximation error with respect to other HOG approaches, thus resulting a more suitable solution for embedded devices. Concerning the state of the art, it also achieves improved accuracy with the mathematical spatial gradient formulation .

Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: Irregular applications present unpredictable memory-access patterns, data-dependent control flow, and fine-grained data transfers. Only a holistic view spanning all layers of the hardware and software stack can provide effective solutions to address these challenges.

Beschreibung: Computer scientist Anil Jain discusses the evolution of the biometric recognition field. The first Web extra at http://youtu.be/Wb_JbpdFoz4 is a video in which Anil Jain talks with Charles Severance about the evolution of the biometric recognition field. The second Web extra at http://youtu.be/_NdKzKybyQ4 is an audio recording in which author Charles Severance reads his Computing Conversations column that discusses his interview with Anil Jain about the evolution of the biometric recognition field.

Beschreibung: A summary of articles recently published in IEEE Computer Society periodicals.

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Beschreibung: Emerging data-intensive applications attempt to process and provide insight into vast amounts of online data. A new class of linear algebra algorithms can efficiently execute sparse matrix-matrix and matrix-vector multiplications on large-scale, shared memory multiprocessor systems, enabling analysts to more easily discern meaningful data relationships, such as those in social networks.

Beschreibung: Work on human self-awareness is the basis for a framework to develop computational systems that can adaptively manage complex dynamic tradeoffs at runtime. An architectural case study in cloud computing illustrates the framework's potential benefits.

Beschreibung: Executing irregular, data-intensive workloads on multithreaded architectures can result in performance losses and scalability problems. Codesigning algorithms and architectures can realize high performance on irregular applications. A codesign study reveals four key lessons learned from implementing matching algorithms on various platforms

Beschreibung: The acronym TSA could just as well stand for "tactics to suppress accountability." It's an object lesson in the misuse of technology toward ill-defined ends.

Beschreibung: A summary of articles published in Computer 32 and 16 years ago.

Beschreibung: Students at the University of Brasília set out to build a better exercise bike. The Web extra at http://youtu.be/NCSb_sDJL7c is a video demonstration of the Bike-X simulator, a virtual cycling experience designed by engineering students at the University of Brasília's Gama Campus.

Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: The Galois system can automatically parallelize irregular algorithms written in a serial programming model and execute them efficiently on nonuniform memory access (NUMA) machines. Experimental results for five complex irregular algorithms show that the system scales up to 420× on large NUMA systems at 512 threads.

Beschreibung: The authors discuss important factors to consider when migrating software to the cloud and offer recommendations to maximize the chance of success.

Beschreibung: We propose novel algorithms that enhance the performance of recovering unknown continuous-valued frequencies from undersampled signals. Our iterative reweighted frequency recovery algorithms employ the support knowledge gained from earlier steps of our algorithms as block prior information to enhance frequency recovery. Our methods improve the performance of the atomic norm minimization which is a useful heuristic in recovering continuous-valued frequency contents. Numerical results demonstrate that our block iterative reweighted methods provide both better recovery performance and faster speed than other known methods.

Beschreibung: The proliferation of electronic means of communication entails distortion of visual information carried by processed images. Therefore, automatic evaluation of image perceptual quality in a way that is consistent with human perception is important. In this letter, an approach to full-reference image quality assessment (IQA) is proposed. The perceptual quality of the image is evaluated using an aggregated decision of several IQA measures. An optimization problem of designing a decision fusion of 18 IQA measures is defined and solved using a genetic algorithm. Obtained fusion strategies are evaluated on widely used large image benchmarks and compared with 32 state-of-the-art IQA approaches. Results of comparison reveal that the proposed approach outperforms other competing techniques.

Beschreibung: As a metric for amplitude fluctuation of orthogonal frequency division multiplexing (OFDM) signal, cubic metric (CM) has received an increasing attention because it is more closely related to the distortion induced by nonlinear devices than the well-known peak-to-average power ratio (PAPR). In this letter, the properties of CM of OFDM signal is investigated. First, asymptotic distribution of CM is derived. Second, it is verified that 1.7 times oversampling rate is good enough to capture the CM of continuous OFDM signals in terms of mean square error, which is also practically meaningful because the fast Fourier transform size is typically 1.7 times larger than the nominal bandwidth in the long-term evolution (LTE) cellular communication systems.

Beschreibung: We propose a new point matching algorithm in this letter by minimizing a concave geometric matching cost function coming from the objective function of the robust point matching algorithm. Due to concavity of this function, naive optimization strategies such as gradient descent will fail. To address this problem, we use a path following strategy for optimization which works by adding a convex quadratic term to the objective function and then gradually transitioning from the state that there is only weight of the convex term to the state that there is only weight of the concave geometric matching cost term. Extensive experimental results demonstrate strong robustness of the method over several state-of-the-art methods and it also has good computational efficiency.

Beschreibung: John Resig discusses the birth of the JavaScript library jQuery and how it came to play a key role in the browser software ecosystem. The first Web extra at http://youtu.be/B7Aut4OUuvs is a video in which jQuery creator John Resig talks with Charles Severance about the birth of the JavaScript library jQuery and how it came to play a key role in the browser software ecosystem. The second Web extra at http://youtu.be/ZRxcFzSqatE is an audio recording of the Computing Conversations column in which Charles Severance discusses his interview with John Resig about the JavaScript library jQuery and how it came to play a key role in the browser software ecosystem.

Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: Numerical dynamic range analysis combines with architectural simulation to help designers explore algorithmic and architectural tradeoffs that can meet embedded computer vision's demand for precision and high-memory bandwidth.

Beschreibung: Students share their impressions of and experiences working with science fiction prototyping at the California College of the Arts. The Web extra at http://youtu.be/c4uYbiH72sI is an audio interview in which Science Fiction Prototyping editor Brian David Johnson talks with California College of the Arts student Gregory Stock about his experience with science fiction prototyping and how it's like exploring dark caves. The second Web extra at http://youtu.be/6XudNL3Cqwo is an audio interview in which editor Brian David Johnson speaks with Leticia Murray, Alida Draudt, and Julia Rose West about their personal experiences working with science fiction prototyping at California College of the Arts. The third Web extra at http://youtu.be/VoJLDiCzH-o is an audio interview in which Science Fiction Prototyping editor Brian David Johnson speaks with California College of the Arts student Jonjozuf Hadley about how science fiction prototyping can give you the space and permission to explore possible futures. The final Web extra at http://youtu.be/xB3RBNT20LM is an audio interview in which Science Fiction Prototyping editor Brian David Johnson speaks with California College of the Arts student Ryan Hogan about one of the most important parts of science fiction prototyping the science fiction.

Beschreibung: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Beschreibung: Evolving from hybrid clouds to true cloud federations and, ultimately, fog computing will require that cloud platforms allow for--and embrace--local hardware awareness.

Beschreibung: The Lunar Atmosphere Dust Environment Explorer (LADEE) software developers incorporated IEEE and other standards to achieve high reliability while adhering to strict budget and schedule guidelines.

Beschreibung: Although GitHub has become a great tool for studying the software development process, it poses afundamental problem to those who study work. The Web extra at http://youtu.be/z7aiYedJr8w is an audio recording of author David Alan Grier expanding on his Errant Hashtag column, in which he talks about how GitHub has become a great tool for studying the software development process but poses a fundamental problem to those who study work.

Beschreibung: Several intellectual property cases this year raise important patent, copyright, and trademark legal questions--the second part of this two-part series focuses on the trademarkand copyright cases. Part 1 is in the April 2015 issue at 10.1109/MC.2015.112. The Web extra at http://youtu.be/3atq5VwO874 is an audio recording of Brian M. Gaff reading the second installment of a two-part series in his Computing and the Law column, in which he discusses several 2015 intellectual property cases that raise important patent, copyright, and trademark law issues.

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Beschreibung: To expand e-commerce, we shouldn't try to fit computing technology into markets, but instead fit markets into technology. The Web extra at http://youtu.be/siTGPpNabHI is an audio recording of author David Alan Grier expanding on his Errant Hashtag column, in which he talks about the disruptive nature of computing and how expanding e-commerce shouldn't mean trying to fit computing technology into markets but instead fitting markets into technology.

Beschreibung: An online inference engine monitors and extracts usage cues from wearables and identifies whether the user is busy, alone, happy, or stressed. Experiments show 85 percent identification accuracy with negligible energy cost.

Beschreibung: This installment of Computer's series highlighting the work published in IEEE Computer Society journals comes from IEEE Transactions on Mobile Computing.

Beschreibung: A summary of articles recently published in IEEE Computer Society periodicals.

Beschreibung: An exploration of current discrimination law reveals new opportunities for promoting the public use of wearable assistive technologies, which can be a powerful impetus for both wearable advocates and researchers exploring design alternatives.

Beschreibung: Three playful wearable accessories incorporate design principles that promote individuality, natural interaction, ubiquity, and intimacy to encourage spontaneous open-ended social interaction in school-age children. The Web extra at https://youtu.be/LBBe8iDeFrs demonstrates Wearable Sound, an accessory that transforms your movements into sounds. You can play the sound of a bird by moving your arms, the sound of bubbles while walking, or create your personal combination. You only have to wear the sensor, choose a sound, and use all your creativity to play!

Beschreibung: A proposed method evaluates eight popular software reliability growth models and selects the one that can best predict the software's remaining faults, providing practical support for project managers who are considering an open source component.

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Beschreibung: A student team from NC State designed and built a prototype wireless network to monitor the milking and weighing of cows.