ALBERT

Description: Correction of speech signals distorted by reverberation is topical in building communications systems, automatic speech recognition systems, and hearing aids. The late reverberation suppression by the spectral subtraction method or the frequency correction method involves the need of estimating the late reverberation spectrum. Though the procedure of such estimation is generally developed, a number of uncertain items related to its optimization still exist. Recommendations elaborated in this study make it possible to optimize the estimation of late reverberation spectrum in terms of such criteria as the speech signal quality and the accuracy of automatic speech recognition by using computer simulation methods.

Description: In this article we consider the general peculiarities of input impedance characteristics. The analytical expressions for the input impedance characteristics have been obtained for the typical wave barrier structures. We present the dependences of the input impedance on the energy for the quantum-mechanical structures and on the frequency for the case of electromagnetic and acoustic structures. Additional conditions to the known ones of resonance transmission and of resonance wave localization, which occur in barrier structures, have been found.

Description: Results of plasma excess conductivity investigations of gas discharge device under conditions of plasma decay have been presented. This case involves the need of taking into account the recombination of charged particles both on the device electrodes and in its volume. It was established that the volume recombination of charged particles at the stage of plasma excess conductivity materially affects the duration of plasma excess conductivity and modifies the pattern of its decay.

Description: In this paper we present the technique for development and calculation of the load network for the microwave class F power amplifier (PA) with addition of the third and the fifth voltage harmonics. The suggested load network compensates negative influence of parasitic elements of the transistor (of output capacitance and of output inductance) on the operation of class F PA. Also the load network allows one to decrease the negative influence of some real properties of the supply circuit shunt capacitor and the blocking capacitor on the impedances, which are created by the load network at the transistor chip. We have obtained the calculation formula for the transistor load resistance at the specified output power for class F PA with addition of the third and the fifth voltage harmonics.

Description: In this paper we have proposed a FinFET based 6T static random access memory (SRAM) cell. FinFET devices can be used to improve the performance, reduce the leakage current and power dissipation. The purpose of this article is to reduce the leakage current and leakage power of FinFET based 6T SRAM cell using various techniques in 45 nm technology. FinFET based 6T SRAM cell has been designed and analysis has been carried out for leakage current and leakage power. For low power memory design the most important problem is to minimize the sub-threshold leakage current and gate leakage current. This work introduces a technique based on threshold voltage, gate oxide thickness and power supply setting together to minimize sub-threshold and gate leakage current of 6T SRAM cell. These simulation results are carried out using Cadence Virtuoso Tool at 45 nm technology.

Description: The phenomenon of spectral equivalence of component Boolean functions of Nyberg-design S-boxes has been investigated. An effective algorithm for removing the spectral equivalence is proposed based on the introduction of random modifier into each component Boolean function of S -box. The analysis of S -boxes generated on the basis of the proposed algorithm corroborates its efficiency and shows high cryptographic quality of S -boxes.

Description: It is proposed a method for increase of reliability of information transmission in wireless networks, functioning in conditions of influence of deliberate noise. The method is based on additional application of uncertainty factor in case of decision making in the turbo decoder in conditions of non-stationarity of the transmission channel. In a process of adaptive regulation of turbo code decoding iterations amount is modified for each data packet basing on dynamic calculation of uncertainty factor. Simulation results show increase of signal to noise ratio results in decoding iteration decrease, and information transmission reliability increase.

Description: Efficient and rapidly convergent numerical algorithm for the simulation of the scattering of light waves by a finite gratings consisting of thin (thinner than the wavelength in the free space) metal nanostrips is presented. The model is based on the utilization of generalized boundary conditions (GBC), which allow one to exclude from consideration the field inside each strip and to reduce the two-dimensional boundary problem to one-dimensional systems of singular/hypersingular integral equations (IE). The obtained IE are solved numerically using the Nystrom-type method and the quadrature formulas of interpolation type, that provides guarantee convergence and controlled accuracy. The article presents the results of characteristics calculations for optical scattering and absorption by the gratings, which consist of silver nanostrips, as dependences on the width and on the thickness of the strips, and on the grating period. The nature of resonance phenomena has been investigated, namely the article presents the analysis of intensive optical scaterring and absorption in the case of excitation of plasmonic modes (plasmons) and of grating modes, which are induced by the periodicity.

Description: Aformula for computing the optimal values of weight coefficients of coherent integration of reflections has been proposed for minimizing the sidelobe level of amplitude-phase characteristics (APC) of Doppler filters applicable at an arbitrary number of such filters. The AFC plots of Doppler filters were calculated and presented for the case of coherent integrator for 8, 12, 16, 24, 32 and 36 filters. The estimated average sidelobe level indicated the validity of specified proposals.

Description: A new general approach to building the filtering methods has been created on the basis of minimum duration principle.Aclass of filtering methods for noisy fixed signals was developed within the framework of this approach. The specified class depends on three freely adjustable parameters and includes the known methods of averaging, median, myriad, and meridian filtering. The efficiency of the proposed approach is achieved by the adjustment of free parameters to their optimal values that depend on the noise scale (dispersion), magnitude of the weight of tails and distribution law waveforms. The general statement and partial statements of the problem of filtering the noisy fixed signal were formulated for a discrete case. The above statements were presented in the form of appropriate optimization problems. Numerical simulation results for the filtering problem of fixed signal distorted by the Gaussian, Laplace, Cauchy noises and mixtures of these noises were also presented.

Description: Paper presents the simulation of processes of spatial localization of objects using systems of radio-frequency identification (RFID systems). The simulation technique for simulation modeling the measuring data of proximity type, received signal strength (RSS) type, and read rate (RR) type obtained from passive RFID-tags has been developed. The technique allows us to carry out the preliminary comparison of localization accuracy ensured in case of using different algorithms of localization and types of measuring data for arbitrary regions of localization. The testing of this technique indicated that the relative error of simulation results as compared to experimental results amounted on average to 8% and did not exceed 28%.

Description: Analysis of electromagnetic waves propagation of various wavelengths in the cloudy and cloudless atmosphere is presented. Attenuation of 0.8, 3.2, 5.6 and 10.0 cm radio waves in the clouds of various forms, different water content and temperatures is demonstrated. Based on the frequence and intensity of the hazards, zoning of Ukraine territory has been carried out. We have performed the substantiation of utilization of 0.8, 5.6, and 10.0 cm wavelengths for radar sounding of the atmosphere in the context of the climate and synoptic monitoring. The recommendations are given on the placement of radar stations of different frequency bands in order to meet the needs for information product of the civil and departmental aviation.

Description: The problem of electromagnetic wave diffraction by the metal objects has been solved using integral equation technique. The diagrams of backward scattering have been plotted for four different objects. Based on the feature vector, which has been constructed by applying wavelet packet signal decomposition, a neural network has been trained. We have performed the testing of ability of the neural network to recognize the object depending on the noise level. Various methods of the feature vector forming have been considered.

Description: In this paper we propose and investigate a unique compact FR4 based CPW-fed tri-band antenna for wireless applications. The antenna comprises frequency shifting strips and a defected ground structure (formed by combining of metallic strips and cutting of an L-shaped slot from the ground). The proposed antenna provides three different impedance bandwidths of 0.57, 0.98 and 1.59 GHz which are sufficient to cover the frequency band of GSM 1800/1900, WLAN 5.5/5.8 GHz and WiMAX applications. The developed antenna has a size of 17-20 mm and operates over frequency ranges 1.50–2.08, 5.25–6.23 and 9.10–10.69 GHz centered at 1.702, 5.802 and 10.102 GHz, respectively. The antenna was designed and simulated using Ansoft HFSS software. The antenna’s characteristics such as reflection coefficient, radiation pattern, impedance bandwidth and VSWR are presented.

Description: Analytical expressions have been obtained for calculating an optimal waveform of the pulse exciting elements of an ultra-wideband antenna array. The criterion of optimality is the minimum of integral side-lobe level. The proposed approach enables us to take into account the signal duration and spectrum limitations and also the impulse response of antenna elements.

Description: The method of current and charge integral equations [1] is applied to numerical electrodynamic analysis of radiation and impedance matching characteristics of parabolic antennas with reflector diameter from 0.5 to 10λ. As a result as opposed to the current method relying on physical optics approximation the influence of feed on reflector’s radiation pattern, the influence of reflector on feed’s impedance matching and the contribution of feed’s rear radiation into reflector’s radiation pattern are all accounted for. A new model of representing a parabolic surface in the form of its square approximation is suggested, which provides almost uniform partitioning grid and has at least 2.5 times less boundary elements that the common revolution surface representation while having the same sampling coefficient. Dependences of antenna’s directivity on reflector dimensions (0.5–10λ) are calculated for six different focus distance to reflector’s diameter ratios using the developed by the authors crystal_U software package. The calculated results are confirmed by good matching with well-known experimental results.

Description: A dynamic coordinate measurements model for an arbitrary target is synthesized using Doppler measurements from three satellites. The model allows conducting posterior estimation using well-known methods of stochastic filtering theory based on code pseudorange measurements.

Description: The paper considers principles of designing an auto-generator with optical channel in the feedback circuit based on magnetic-optical crystal, in which magnetic-mechanical oscillations take place. A reference design of auto-generator based on yttrium iron garnet is provided along with its experimental research results.

Description: It is presented is the possibility to solve the inverse variation problem based on the determination of a primary functional by the results of minimum mean-square error in optimal linear filtering of the signal theory.

Description: A composite matrix cipher consisting of four partial ciphers and based on perfect binary arrays has been proposed. This cipher possesses an easily controlled level of data protection from unauthorized access and other practically acceptable computational properties.

Description: The strict expression for probability of a false alarm of is maximal likelihood algorithm of detection of rectangular radiopulses with unknown amplitude and duration is found by means of solution of the Fokker-Planck-Kolmogorov equation with division variables method. In contrast to known before solution, the expression is correct for any detection thresholds and arbitrary a priory value of definite interval of durations.

Description: Characteristics of efficient estimates of the range, velocity, and acceleration of a rapidly fluctuating target have been obtained during the probing with a sequence of optical pulses. The losses in estimation accuracy of the range, velocity, and acceleration caused by the presence of non-informative parameters have been also found.

Description: Asymptotic expressions for the characteristics of quasi-likelihood estimation of image area have been obtained by using the local Markov approximation method. It was shown that the accuracy of area estimation is determined by the magnitude of intensity jump over the boundary limiting the area occupied by image.

Description: This paper considers a phase recovery method for the coherent carrier frequency of the signal Revised by a digital receiver using a unit of digital recovery of the coherent carrier phase. The use of digital phase filter makes it possible to do without the application of traditional phase-locked loop frequency control. The paper also presents a technique for deriving a transfer function of the specified digital filter and considers the issue of its robustness in relation to self-excitation. In addition, the paper presents a functional diagram of this filter.

Description: Simplified expressions are obtained for the calculation of the eigenfrequencies of a biconical cavity with large apex angles with the use of two symmetrical points at the boundaries of overlapping partial regions in the form of a spherical sector. Using these expressions, the dependence of the cavity eigenfrequencies on the apex angles of the conical elements is studied, and the results are compared with those obtained by the classical finite-element method. The applicability range of the simplified expressions is identified, and recommendations on their use are given.

Description: Acomparative analysis of the noise immunity and computational complexity of variousGSM signal demodulators in the analyzer of base stations has been carried out, and recommendations were provided for the selection of demodulator depending on the signal environment and acceptable complexity of its implementation.

Description: Two new presentation forms of multilevel de Bruijn sequences (BS) have been introduced as geometric and algebraic structures. The attractive and practical properties of these structures have been found. This formed the basis for proposing a constructive method for the synthesis of generating and complete classes of BS. It has been shown that the application of the found classes of quaternary BS in encryption ensures a two-fold reduction of the memory space required for storing the cryptographic substitution boxes (S-boxes).

Description: Linear programming (LP) decoding is an alternative to iterative algorithms for decoding low density parity check (LDPC) codes. Although the practical performance of LP decoding is comparable to message-passing decoding, a significant advantage is its relative amenability to nonasymptotic analysis. Moreover, there turn out to be a number of important theoretical connections between the LP decoding and standard forms of iterative decoding. These connections allow theoretical insight from the LP decoding perspective to be transferred to iterative decoding algorithms. These advantages encouraged many researchers to work in this recent decoding technique for LDPC codes. In this paper, LP decoding for LDPC code is extensively reviewed and is discussed in different segmented areas.

Description: The paper considers various structureless inertial non-linear models of power amplifiers and methods of their identification. Based on polynomial model with memory and Volterra model the influence of different kinds of input signals, their bandwidth and average power on precision of power amplifier modeling and complexity of model implementation.

Description: Carrier frequency offset (CFO) due to Doppler frequency shift or frequency mismatch between the transmitter’s and receiver’s oscillators can introduce severe inter-symbol and inter-carrier interference into OFDM systems. A simplified OFDM system model is considered to analyze effects of CFO in theory and simulation. The article briefly reviews some traditional CFO estimation algorithms. Relying on relatively good correlation characteristic of pseudo-noise (PN) sequence, the PN preamble based algorithm of CFO estimation is developed. Performance characteristics of traditional and the new improved algorithms are simulated under different conditions. Results indicate that the PN preamble based algorithm of CFO estimation is more accurate, resource-saving and robust even under poor communications channel condition, such as low SNR and big normalized CFO.

Description: Characteristics of quasi-likelihood estimates of the target range, velocity, and acceleration have been obtained during the probing with a sequence of optical pulses. The losses in accuracy of quasi-likelihood estimates as compared with the accuracy of maximum likelihood estimates were also found.

Description: This article presents a numerical solution for radiation from a novel coaxial horn with a partial dielectric loading. The horn is represented as a set of three-layer dielectric loaded coaxial waveguide sections. Characteristic equation has been obtained to calculate phase coefficients for hybrid modes in each section. Applying mode matching technique generalised scattering matrices for each junction between the sections have been obtained, besides that power coupling integrals for each of three different type of junctions have been found in closed-form solutions. Cascading these scattering matrices with transmission matrices of each section yields a generalised scattering matrix of the horn. For the given excitation at the throat of the horn, amplitude and phase of eigenmodes at the aperture of the horn have been determined. Finally, Fourier transform integral of the aperture electric field has been applied to solve radiation problem of the horn. Numerical results on propagation and radiation characteristics of the first four hybrid modes of the horn are presented and it is validated that this solution can be successfully used for full-wave electromagnetic analysis and optimisation of multiband dielectric loaded coaxial feeds.

Description: The absolute maximum of Gaussian Markov’s stationary process is obtained by means of solution of the Fokker-Planck-Kolmogorov equation with method of variables division. It is shown, known results are special cases of obtained solution. The probability of process location in one of half-plane of its values is specified.

Description: A compact ultra wide band pass filter has been proposed in this paper. The band pass operation of the filter has been obtained with the combinations of high pass filter and low pass filter. The low pass filter used in the combined structure is designed using the triangular patch resonators and the high pass filter is designed using shorted stubs. The three different topologies to combine the low pass and high pass filter are compared. The final structure gives a very compact configuration of ultra wide band pass filter. The design methodology of the proposed filter is elaborated. The designed structure is simulated and fabricated. The group delay of the filter gives almost flat for the entire operation band. A good agreement has been seen between simulated and measured values of scattering parameters. The fractional band width has been achieved as 130%.

Description: The results of experimental investigation for determining the effect of different factors (distance between contacts, type of contacts, and the grade of virgin wafers) on the origination of stable oscillations of high amplitude current in long planar-epitaxial structures based on high-impedance semi-isolating n -type gallium arsenide have been presented. It was found out that the distance between the anode and cathode contacts was a key factor determining the emergence of stable oscillations of high amplitude current in such structures.

Description: It is solved a problem of a posteriori estimation of dynamically modified parameters of angular movement of the object by satellite measurements. There are shown advantages of application of the methods of stochastic non-linear dynamic filtration before single-stage measurements. It is represented an example, showing efficiency of proposed approach.

Description: This article presents the results of numerical investigation and optimization of matching and radiation characteristics for a single planar quasi-Yagi antenna and for a planar phased antenna array (PAA) with size 11×11 elements, which is designed based on these radiators. The research has been performed utilizing the finite difference time domain technique. The calculations have taken into account the presence of an additional metal screen behind the radiating curtain and the feeding of each array’s element via the coaxial-to-microstrip transition, that has made the model of an array as close as possible to the real PAA design and to its performance under real conditions. The levels of electromagnetic coupling between adjacent array elements have been investigated, the variations of operating characteristics of elements in its structure have been demonstrated in the case of in-phase excitation and in the scanning mode. It has been found that the possible scanning sector of this screened PAA falls within the range ±45° for the reflection coefficient of any array’s element, which is less than −10 dB in the frequency range not less than 10%, and for the central element of an array the corresponding operation frequency range exceeds 30% for the scanning in E -plane and it is larger than 17% for the scanning in H -plane.

Description: This paper presents a simple end-fire ultrawideband dipole-slot antenna, which consists of a single plate dipole located above the screen and loaded by two slots, that are formed by three metal sheets. The results of numerical investigation of its matching and radiation characteristics using integral equations technique for the current and the charge are demonstrated in the article. An optimized variant of the antenna has a low profile (0.17λ max ) and in the frequency range with bandwidth ratio 3.2:1 it provides VSWR〈2in the case of excitation by the 50Ω feeder, and also it provides almost unalterable shape of the radiation pattern for the wavelengths, which are close to the λ/2 distance to the screen, what cannot be obtained for the dipole antenna above the screen. It has been shown that such an effect is achieved due to the in-phase combining of the radiations emitted by the dipole-slot system and by the screen in the front half-space.

Description: A new technique of implementing dual-bandpass filters built on rectangular dielectric resonators has been proposed. The possibility of simultaneous tuning of two passbands on one structure of coupled dielectric resonators using their intrinsic high-mode oscillations was investigated for the sake of reducing the size of design. The proposed analytical solution was compared with the results of simulation by the finite element method. Coupling coefficients of rectangular resonators were calculated and investigated by a numeric technique for the low dipole TE 01δ and high quadruple TE 02δ magnetic modes depending on the parameters of filter design. The proposed dual-bandpass filter built on dielectric resonators can be used in base stations and wireless access points of communication networks.

Description: It is carried out comparative analysis of the methods of research of photo-electric response on example of scanning of semiconductor structure of laser diode on a basis of AlGaInP in direction, which is perpendicular to p-n junction plane. We discovered and theoretically proved a difference in results obtained by means of phase and differential-phase research methods. It is shown differential-phase research method allows to obtain addition information about optical properties which are not present in results, obtained by phase method.

Description: It is considered a possibility of build of communication system, which can function in conditions of influence of pulse or concentrated interference with enough great level in compare to useful signal. For increase of noise-immunity of such systems we propose an interrupted operating mode, when information is transmitted only in case of signal-to-noise ratio is greater than definite threshold value. It is represented calculation of the system proposed efficiency in compare to known ones.

Description: Peculiarities of the modulation of optical radiation during the excitation of magnetomechanical oscillations in a composite structure consisting of magneto-optical crystal and magneto-passive layer have been studied. Analytical expressions for the amplitude- and phase-frequency characteristics of a magneto-optical light modulator based on the Faraday effect for a low-frequency mode under conditions of magnetomechanical resonance were obtained. The results of theoretical and experimental investigations of a modulator in the form of bilayer composite structure consisting of yttrium iron garnet and quartz glass were presented. The relative change of the amplitude of polarization plane rotation in the region of resonance frequencies at the level of 25% and the phase delay of 22° were obtained experimentally.

Description: We present results of theoretical and experimental investigations of a novel dual band right hand circularly polarized microstrip antenna array with adaptive space-time processing capability for terminal of GPS/GLONASS/GALILEO satellite navigation systems. The array structure is composed from 10 microstrip radiators excited independently via separate coaxial input ports. Two central radiating elements for two frequency bands (L1 and L2) have got circular shapes with slits and are stacked to provide compact sizes and coincidence of their phase centers. Peripheral radiators have got annular ring shapes with slits topology. The main feature of the array is its compact packaging of radiating elements that causes significant levels of electromagnetic mutual coupling. Geometric parameters of the array were selected using high-efficiency multi parametric particle swarm optimization to provide optimum performance of each radiator in the compact array packaging. Moreover, several right hand circularly polarized radiators of the array assembly were rotated around their centers to improve their characteristics and to increase the quality and effectiveness of space-time processing of adaptive antenna system. The novel design of the dual frequency right hand circularly polarized array and somewhat imperfectness of the obtained characteristics are experimentally validated.

Description: The problem of enhancing the effectiveness of spectral analysis of signals observed against the background of noise by the Root-MUSIC method has been considered using the surrogate data technology implemented by adapting the algorithm of phase randomization of the Fourier transform samples of the initial data in relation to the signal-to-noise ratio (SNR). The proposed variant of the surrogate data technology was shown to be effective at low values of SNR and a small number of samples. At large values of SNR an additive variant of the surrogate data technology actually does not cause an emergence of surrogate interference typical for nonadaptive variant. The proposed variant of the technology can be applied in combination with other methods of spectral analysis.

Description: Errors in measuring the electromagnetic field parameters of a five-element antenna system have been analyzed. Analytical relationships for main errors were derived, and maximum values of measurement errors were calculated.

Description: Thepaper considers classification, design concepts and circuit engineering of radiofrequency identification devices. A survey on circuit designs for the readers and passive tags of the system is presented. The survey results indicate the perspectivity of implementation of particular communications protocols and of ultrawideband systems in order to provide multiple access under the collision conditions.

Description: A coherence function characterizing the correlation between harmonic components of two signals that are described by periodically correlated random processes has been proposed. Such function is shown to be invariant with regard to linear transformations of signals.Aformula for coherence function is concretized for the amplitude- and phase-modulated signals.

Description: In this article we investigate the characteristics of a quasi-likelihood estimation of the time of arrival and the repetition period of ultrawideband signal of unknown form, which is received on the background of narrowband interferences with unknown parameters and of Gaussian white noise.

Description: This paper presents three transistors (3T) based Dynamic Random Access Memory (DRAM) cell in which noise, static power, and data retention voltage (DRV) have been reduced. The spesified parameters in the proposed eDRAM gain cell were improved by connecting the source of storage device to the read word line signal instead of supply voltage. As we all know, power consumption plays a vital role in VLSI design and thus, it is enumerated among the top challenges for the semiconductor chip industries. With the intention to maintain the performance of write operation, we diminish DRV and increase the read margin of eDRAM cell with our designed circuit which is introduced as “A Boosted 3T eDRAM gain cell”. It is a kind of eDRAM cell that utilizes a read word line (RWL) via three PMOS transistors instead of NMOS transistors. PMOS devices are preferred as they have radically less gate leakage current, which confer better results for data retention and thus, boost up the read margin of the cell. Simulation results have been obtained by using Cadence Virtuoso Tool at 45 nm technology for the proposed model. Based on simulation results we can conclude that the parameters of the proposed eDRAM gain cell essentially improved as compared with convertional eDRAM gain cell and the achieved parameters are as follows: static power is 0.767 pW, DRV is 142.009 mV and noise is 8.421 nV/Hz 1/2 .

Description: This is the first paper in a series of papers devoted to the peculiarities of estimation of the continuous energy spectra of random processes of different nature, which are defined by their samples at discrete moments of time. In the paper we consider two kinds of the generalized spectrum analyzers (GSA), whose structure fits the majority of classical (nonparametric) and modern noneigenstructured spectral estimation (SE) methods. It has been demonstrated that a number of known superresolution SE methods may be considered as particular cases of parametric GSA based on whitening or inversing filters of the input process. We focus on the autoregressive models of analyzed processes with continuous energy spectrums, for which the whitening or inversing filters are the transversal filters of various structures with proper parameters. The utilized interpretation allows one to modify the well-known superresolution SE methods for the problem of continuous spectrums reconstruction and, what is more important, to establish their new varieties with practically useful properties, that are going to be explored in the following two papers.

Description: Theoretical analysis of the oscillation synchronization under conditions of simultaneous low-frequency and high-frequency external impact on the oscillator has been conducted using an example of the generalized Van der Pol oscillator. It was shown that the interaction of high-frequency and low-frequency oscillations resulted in the appearance of additional regions of synchronization as a result of three-frequency interaction between the frequencies of such interaction and the natural frequency of oscillator. For the case of three-frequency interaction, characteristics of synchronous oscillations were determined and compared with those for the case of primary tone synchronization of oscillator.

Description: Composites provide possibilities to combine the properties of different materials in order to obtain materials with the necessary parameters (low loss, absorbing, reflective materials, etc.). According to their structure, composite materials are conventionally divided into the microtextures and macrotextures. In turn, these materials may be passive or active. The properties of passive composite materials are invariable, and the properties of active ones can be altered using different effects: electric, magnetic, thermal, etc. In this article we present the results of theoretical and experimental investigations of various microwave dielectric-based composite structures. Particular attention is given to high-Q microwave structures with electrical control.

Description: The paper presents research of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10% during tuning due to reduction of dielectric loss in substrate’s medium and ohmic loss in metal electrodes. When total loss in the device is relatively small, loss mechanisms contribute additively, so complex effective permittivity can be used to account loss reduction and frequency tuning.

Description: In this article we have synthesized multilayer contact systems Ti/Ag and Ti/Mo/Ag with nanostructured silver films using two vacuum methods, namely the method of electron-beam evaporation and HF magnetron sputtering. Using the data of atomic force microscopy, X-ray diffraction and mass spectroscopy of the secondary neutrals in the paper we have investigated the influence of the application method and of the annealing conditions on the grain formation processes in silver thin films and mass transfer between the metal layers of the contact system. The decrease of surface resistivity of the developed contacts and, respectively, the increase of short-circuit current of the heterojunction silicon solar cells have been determined.

Description: In this paper we present the method for determination of the specific auscultatory diagnostic signs in patients with chronic obstructive pulmonary disease (COPD), which is based upon the utilization of the polyspectral analysis and the calculation of higher order statistics. The main stages of the method are the calculation and construction of the bicoherence function of the lung sound signal in order to find its maximal value. The visual and numerical estimations of the obtained maximum allow us to conclude the presence or absence in this lung’s audio signal of the artifact, which indicates the pathology. For more accurate results one needs to determine asymmetry coefficient and to perform the estimation of bifrequency corresponding to the maximal value of the bicoherence coefficient. The calculation of skewness and kurtosis coefficients of cross-correlation functions of lung sound signals, which were recorded simultaneously in four channels, allows us to reduce the sensitivity of the method to noise components. Therefore, by analyzing all proposed calculated characteristics and parameters one can conclude the presence or absence of the pathology in this audio signal.

Description: 〈h3〉Abstract〈/h3〉 〈p〉Statistical characterization of ground clutter information for radar systems is a topic that requires a detailed understanding. In this work, we characterize the ground clutter information from data captured by two Frequency Modulation (FM) based passive radar systems placed at different locations in the Czech Republic. Since the target models are statistically defined by the Swerling models, each of which is based on a particular distribution, we attempted to connect the ground clutter with some of the known distributions. The analysis is performed in three steps. The empirical distribution is fitted with some of the well-known distributions. Two different goodness-of-fit tests (named chi-squared test and Kolmogorov-Smirnov test) are performed on the obtained data by comparing the empirical distribution with the fitted distributions to determine which distribution is the best fit. The observations are analyzed and the results are considered in detail.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In the modern age, wireless communication has taken on a wide range of applications in different aspects of a human life. Ever increasing demand for higher data rates led the interest of research in FBMC (Filter Bank Multi-Carrier) as a new transmission system for the next-generation mobile communication system. FBMC is a multicarrier technique which utilized filters at the transmitting and the receiving side of the system. It is considered as one of the most promising waveform for fifth generation mobile communication system (5G). But, high value of Peak Average Power Ratio (PAPR) is considered to be one of the giant problems in FBMC. The PAPR reduction techniques used in OFDM cannot be utilized in FBMC due to its overlapping structure. Hence, new PAPR reduction techniques for FBMC have diverted the attention of researchers. In this work, dispersive selective mapping (DSLM) PAPR reduction technique is proposed. Further, the proposed technique is compared to selected mapping (SLM) and clipping PAPR reduction techniques. The simulation results show that the proposed DSLM technique gives the better performance in terms of bit error rate (BER), PAPR and complexity as compared to the SLM and clipping PAPR reduction techniques.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this article an S-shaped rectangular microstrip patch antenna (RMSA) is investigated for S-band applications using artificial neural network (ANN). The authors have done the parametric study of different radiating structures to obtain S-shaped RMSA. The size of inserted notches on the radiating patch for achieving wideband operation is computed through multilayer perceptron artificial neural network (MLP-ANN) over a desired range of its performance effecting parameters such as frequency, gain, directivity, antenna efficiency, and radiation efficiency. MLP-ANN model is trained and tested with seven different algorithms. The research found that Levenberg-Marquardt (LM) training algorithm takes less computational time with better accuracy for computation of notches size on radiating patch over a priory defined performance parameters. To verify the work, a prototype of S-shaped RMSA is physically fabricated on foam substrate and tested experimentally. The experimental results are in good agreement with the simulated results that are produced with ANN.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Recent advances have demonstrated that multiple-input multiple-output (MIMO) wireless technology can achieve impressive enhancement in overall system performance. It offers spatial multiplexing and spatial diversity without increasing either the total system power nor the bandwidth and thus offering the potential for substantial improvements in channel capacity and spectral efficiency. However, the high dependence of its channel capacity on the correlation between antenna elements represents the main drawback of MIMO systems. Therefore, multi-polarized antennas have been implemented in these systems to reduce the antenna correlation and realize compact devices. This article is intended for the hybrid diversity (space and polarization) performance analysis of MIMO channels in indoor environment under non-line-of-sight (NLOS) condition. It investigates the effect of inter-element spacing on the cross-polar discrimination (XPD) and co-polar ratio (CPR). In this regard, the capacity as well as bit error rate (BER) performance of hybrid MIMO system is analyzed to draw a fair comparison between it and dual polarized along with spatial diversity techniques. The simulation results show that the hybrid diversity has a middle performance between these two scenarios of system implementations. Additionally, the performance of hybrid diversity is clearly enhanced in comparison with the dual polarized condition of operation, as the separation between the antennas increases. Moreover, as a function of the antenna separation, the spatial diversity system performance is varying slower than that of hybrid diversity case.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The article presents the development results of the hybrid-integrated waveguide-planar amplifier circuit for 8-mm wave range with spatial power combining. Affordable and inexpensive low-noise UMS CHA2494-QEC integrated amplifiers are used in the developed circuit. To improve the efficiency of power combining, new longitudinal probe transition designs from a rectangular waveguide to a coplanar strip line (CSL), and to a microstrip line (MSL), whose dimensions do not exceed 0.4λ〈sub〉0〈/sub〉, are proposed. As a result of the amplifier electromagnetic system development, a high efficiency of power combining has been achieved up to η ≈ 85%. The paper presents the experimental results of phase-shift keyed signals transmission through the developed amplifier with a signal level that is slightly lower than the level of 1 dB gain compression. On the basis of the proposed model, the amplifier degradation was also theoretically investigated for various failure modes of one of its active elements.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Equivalent circuit model of a coaxial probe-fed quasi-lumped element resonator antenna is proposed. The proposed resonator is a periodic interdigital lumped element structure whose resonance does not depend on the electrical length but instead on some intrinsic circuit components, with attendant small size as a premium. The derived equivalent circuit components are extracted using the Agilent Advance Design System (ADS) software. The equivalent circuit model of the coaxial-feed probe is derived based on the simplest uniform-current model of a coaxial probe based on assumption that 1) all the higher-order evanescent have been included analytically in the parasitic circuit elements, and 2) only the propagating modes needs to be considered. The entire structure is further investigated using numerical EM solver such as finite integration technique (FIT) method in order to further compare the level of agreement. The derived equivalent circuit model has been validated by analytical formulae, numerical simulations, and measurement-based method.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Thepaper proposes a nonlocal method of additive noise suppression in digital image based on presenting the image in matrix phase space and using nonconventional methods of multivariate statistical analysis, namely, the surrogate data technology that makes it possible to generate a pseudo-ensemble of surrogate images with their subsequent averaging using a single snapshot. This approach is based on properties of the coherent accumulation of signal component of the observation and noncoherent accumulation of its noise component as the size of observation ensemble increases that allows us to partially solve the contradiction between the denoising level and the distortion or loss of small-sized details of image, i.e. reduction of spatial resolution. The simulation modeling of the proposed method of generalized SDT-filtering of noise was conducted using the application software package of MathCad and Matlab. A comparative analysis of the spatial resolution of the proposed and several known methods of denoising has been carried out using the resolution-measurement criterion and the modified Rayleigh criterion. As is shown, the proposed method demonstrates a better spatial resolution as compared to the most common methods of denoising that is confirmed by the results of simulation modeling.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Oscillators with the primary tone synchronization and based on the frequency-divider mode have been considered in this study. The paper proposes a generalized model of injection-locked oscillator using the linear polynomial approximation of nonlinear characteristic of its amplifying element, and a new analysis technique based on peculiarities of the oscillator operation in injection-locked mode. These peculiarities imply that the oscillation amplitude can be considered as steady-state at an arbitrary instantaneous value of phase shift and that the curvature of phase characteristic of the oscillator decreases with the rise of synchronization signal amplitude within certain limits. The development of the new technique involved the use of the linear approximation method of reduced equations of injection-locked oscillator and the small parameter method. The new technique is insensitive to the form of nonlinear terms, and it allows us to obtain analytical solutions of reduced equations having different nonlinear terms that depend on the oscillator operation mode. This technique features small errors and essentially simplifies the investigation of injection-locked oscillators and their systems. The experimental test confirmed its high efficiency.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The article analyzed the possibility of the appearance of an acoustic information leakage channel that is formed by analyzing the video stream on the video record. The authors investigated the possibilities of speech recovery from a low quality recording, determined by the signal-to-noise ratio (SNR), sampling frequency, number of quantization levels, and clipping level, taking into account the features of the leakage channel under study. As a result, the required frame rate of the video image, the minimum SNR, the number of quantization levels, and a sufficient dynamic displacement range of the oscillating object are determined. The authors also investigated the requirements for the leakage channel parameters and possible ways for an attacker to improve its quality. The requirements for the displacement of an object oscillating under the action of acoustic waves in a video were calculated. The article justified the potential of reducing the requirements for the displacement of an object by applying averaging of a large number of different points on the object. The authors performed an assessment of the existing noise reduction software for sound recordings, which is used to increase the intelligibility of the message that is intercepted by the attacker in the considered information leakage channel. Obtained results revealed that there are potential causes for the leakage of acoustic information by analyzing the video stream on the video. The conditions for the emergence of such a channel are not excessive. Therefore, the possibility of its appearance is a security risk and it is necessary to provide the means to protect the object of information activity from it.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The methodology of simulation of high voltage glow discharge electrodes’ systems with anode plasma, formed the profile electron beams with the ring-like focus, is considered in the article. The universality of proposed model is confirmed by the fact, that the slope angle of generatrix line of conic anode surface correspond to the axis of the electrodes system have been chosen as one of model parameters. Such novel solution has led to simulating the different types of electrodes’ systems, which form the profiled electron beams. The position of plasma boundary in considered high voltage glow discharge electrodes’ systems is firstly calculated on the basis of one-dimensional model of discharge gap, and after that recalculated with taking into account the real geometry of electrodes’ system. Such approach allows to significantly simplify the proposed mathematical model and to avoid using the sophisticated iteration numerical methods for defining plasma boundary form and position without decreasing the accuracy of simulation results. The results of simulation of plasma boundary position are compared with obtained experimental data and disagreement between simulation and experimental results is nearly 10–15%. The results of simulation of distribution of electric field in the cathode-fall region as well as results of simulation of distribution of beam current density in the ring-like focus of formed hollow electron beam are presented in the article. The simplicity and universality are the main advantages of the proposed model.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The excitation of short electric monopulses of space charge waves with wide frequency spectrum of terahertz range in nitride films has been theoretically investigated. The excitation of these pulses with duration ≤ 5 ps and high peak values of electric fields is possible in 〈em〉n-〈/em〉GaN or 〈em〉n-〈/em〉InN films of submicron thickness in the presence of negative differential conductivity. The simulation of nonlinear dynamics of pulses was performed with due regard for the nonlocal dependence of the drift electron velocity on the average electron energy. Optimal values of the applied constant electric fields and equilibrium electron concentration for excitation of monopulses are specified. The monopulse dynamics is weakly dependent on the film width and also on the value and waveform of input excitation pulses. Short electric monopulses differ from domains of strong electric field in Gunn diodes built on bulk crystals with negative differential conductivity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this article a ring voltage controlled oscillator (VCO) with four stages consisting of differential delay cells with two control voltages is proposed. This VCO uses the dual-delay loop technique for high operation frequency. Each delay cell of the proposed VCO includes two pairs of PMOS and NMOS cross-coupled load transistors to form a latch. The strength of the added latch and the operation frequency are adjusted with a pair cross-coupled NMOS pass transistors. Furthermore, to adjust the frequency of the proposed VCO in higher frequencies, the effect of the secondary path of this VCO is changed. The proposed VCO is simulated in 65nm TSMC CMOS technology in Cadence software and 1.2 V supply voltage. The wide tuning range of the proposed VCO varies from 4.25 to 21.31 GHz (80.07%), its power is 12.36 mW at 4.25 GHz frequency. The phase noise is −90.47 dBc/Hz at 1 MHz offset frequency and −117.4 dBc/Hz at 10 MHz offset frequency from 4.25 GHz while its area is 535.99 µm〈sup〉2〈/sup〉.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Now there is a tremendous growth in the specific applications positively related to wireless communications, which posses the specific requirement for mixed-signal integrated circuits. When these independent circuits are used in the unique design of ADC and DAC practical applications, the considerable complexity of the testing increases. BIST is a precisely conventional technique which typically reduces this considerable complexity and prevents functional dependence on high-cost test equipment ATE. Moreover, in Built-In-self-Test (BIST), the output response analyzer (ORA) is the most significant component of architecture of continuous time (CT) sigma-delta analog-to-digital converter (ADC). There are numerous techniques of ORA used for accurate determining the design parameters like integral non-linearity (INL), differential non-linearity (DNL), signal-to-noise ratio (SNR). In this paper, the prime focus is primarily on the modern CORDIC technique which is used as ORA. For the modelling and accurate simulation of this technique Matlab simulink and CADENCE VIRTUOSO EDA tool environment software are properly implemented. A Coordinate Rotation Digital Computer (CORDIC) reduces the design complexity of the independent circuit. The design of ADC can be improved tremendously by typically using BIST. This paper focuses on the system level modelling of test stimuli generator (TSG) and its simulation for accurate characterization of high-resolution sigma-delta ADC. The successful implementation is carefully tested on Matlab simulink tool environment. The auto-testing external test equipment is required to test the integrated structures. TSG is implemented and it helps in extracting of statics and transmission parameters required for characterization of CT sigma-delta ADC.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effective filtering of noisy signals is one of the topical and open problems of the processing of noisy signals characterized by the presence of pulse interferences. A robust approach to intensity estimation of noise-like signal in the presence of additive uncorrelated pulse interferences has been proposed. The presence of additive uncorrelated pulse interferences leads to an increase of dispersion of registered signal at separate sections with pulse interferences. The robustness of intensity estimation is achieved by reducing the influence of sections with pulse interferences. A variety of nonlinear filtering methods has been developed that are based on detecting the intensity using lower envelope: two-parameter recursive filter, dilation, limiting the derivative and order statistics. The numerical simulation was used to perform their comparison with the known most common methods. The numerical simulation confirmed the efficiency of the approach proposed for estimating the intensity of noise-like signal in the presence of additive uncorrelated pulse interferences. The developed techniques can be applied for signal processing in means of communications, measurement instrumentation, radio astronomy, and also for image processing.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper presents a wideband Sierpinski carpet fractal patterned rectangular Dielectric Resonator Antenna (DRA) operating in the X-band, which is characterized by dielectric waveguide model method (DWM). In order to decrease the cost of theDRAthe low-cost teflon is used as the material. Aprototype is realized to validate the results of the simulation. The paper provides a comparison between conventional rectangular DRA and fractal shaped rectangular DRAs of the first and the second iterations. The antenna design methodology is discussed along with its resonance and radiation characteristics. The validity of the obtained results is proved by the close match of the experimental and simulation results. The measurements on prototype show impedance bandwidth of 48% covering the entire X-band with similar radiation pattern throughout the band with a gain of 7.5 dBi over 9.0–11.5 GHz.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The sum-rate performance of a massive MIMO system is dependent on the adequate user and antenna selection techniques. It is best when all the selected users are mutually orthogonal (MOU) and antennas are selected based on maximum channel gain. In the case, when number of antennas in massive MIMO is approximately hundreds, the computational complexity cost in joint user and antenna selection is very high. Semi-orthogonal user selection (SUS) is preferred to reduce interference and complexity cost. In highly scattering Rayleigh fading channel random user selection (RUS) technique can be used because of small loss of system sum-rate compared toSUSandMOUtechniques. In this paper we propose a joint user and antenna selection algorithm where users are scheduled using semi-orthogonality measure and antenna selection is based on maximum channel gain. In addition, an algorithm for joint user and antenna selection is reported here with RUS for user selection and maximum channel gain for antenna selection. We explore the system sum-rate performance of a massive MIMO system using these algorithms for the case of a highly scattering Rayleigh fading channel. We consider various precoding techniques MMSE, ZFBF, and MRT and a range of SNR. We also explore the effect of spatial and multiuser diversity on system sum-rates using proposed algorithms. The sum-rate obtained by algorithms-1 is greater than the algorithm-2 about 1–3% but second one is much simpler.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The paper presents a rigorous solution of the electrodynamic problem for 〈em〉T〈/em〉-type waves in a coaxial waveguide of elliptical cross-section. The solution was obtained using the original modified elliptical coordinate system. The advantages of this approach are convenient expressions for the electrodynamic characteristics of the transmission line and a simple transition to a particular case of a circular waveguide. The authors have obtained explicit expressions for the impedance, transmitted power and propagation losses of the coaxial elliptical waveguide with 〈em〉T〈/em〉-type waves, and have analyzed their dependences on the size and shape of the cross-section of the transmission line. The graphs of the dependences of these characteristics on the normalized parameters that define the shape and size of the waveguide allow choosing the geometric dimensions of the transmission line based on the requirements of a given characteristic impedance, limiting transmitted power or losses. It is shown that at large eccentricities, the energy in waveguides with similar sizes of internal and external conductors and low wave resistance is concentrated near the foci, which allows using such waveguides as the basis for developing effective probes for radio-spectroscopic studies.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Modern radars have adopted adaptive processing techniques to mitigate the deleterious effects of unwanted clutter and jammer. In this situation, the CFAR algorithms play a vital role in achieving the heterogeneous detection of fluctuating targets. In this regard, while the CA-CFAR processor has the top homogeneous performance, the OS and TM techniques have been suggested to provide robust estimates of the threshold in heterogeneous situations. In order to simultaneously exploit the merits of CA and OS or TM processors, some their hybrid versions have been recently introduced. They are termed as CAOS and CATM models. Practically, the frequency diversity between noncoherent sweeps is widespread in actual radar systems. Additionally, the pulse integration strategy is often used in radar systems to improve the target signal-to-noise ratio and correspondingly the system detection performance. For this reason, this paper is focusing on analyzing these new models in the case where the radar receiver noncoherently integrates 〈em〉M〈/em〉-pulses to handle its detection. Closed-form expression is derived for their nonhomogeneous performance. The tested as well as the spurious targets are assumed to follow χ〈sup〉2〈/sup〉-distribution with four degrees of freedom in their fluctuations. Our simulation results reveal that the new version CATM exhibits a homogeneous performance that outweighs that of the classical Neyman-Pearson (N-P) procedure, which is employed as a baseline comparison for other strategies in the field of adaptive detectors.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The problem of distinguishing random signals with similar spectral and correlational characteristics is considered. To solve this problem, a criterion for a minimum of the mean divergence of the hypotheses taken with respect to the true distribution in the Kullback–Liebler information metric is proposed. Using this criterion, an optimal algorithm is synthesized, which allows achieving a guaranteed efficiency gain in discriminating random signals of similar structure. An example of its implementation in the problem of automatic speech recognition at the basic, phonetic level of signal processing is considered. Estimates of its effectiveness are obtained. Theoretical estimates of the effectiveness are confirmed by the results of the experiment. The author’s special-purpose information system was used for this. On the basis of the obtained results, recommendations are given for the practical application of the proposed criterion in problems of statistical signal processing, where a problem of verifying close statistical hypotheses arises.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Adaptive systems protecting pulse radars from non-stationary in time (range) clutter echoes are usually tuned using training vectors composed of complex amplitudes of input signals and comprising a finite-length “sliding window” of data. From any current range gate to a subsequent one, a training sample is partially updated (or modified) by means of excluding the “old” training vectors (correspond to the current range gate) and including the “new” ones (correspond to the next range gate). As a consequence, respective estimates of adaptive system parameters are corrected according to a modified sample correlation matrix (CM), which is typically a sum of an initialCMand a modifying matrix of rank 〈em〉K〈/em〉 ≥ 1. In this case it is possible to avoid re-computing these parameters based on a new training sample of full size and, instead of this, we correct them in an “economical” way employing 〈em〉K〈/em〉-rank modification of a matrix inverse to the CM estimate.〈/p〉 〈p〉This paper is devoted to comparative analysis of various (〈em〉K〈/em〉 ≥ 1)-rank modification algorithms that correct the parameters of adaptive lattice filters (ALF). Main attention is paid to synthesis as well as theoretical and experimental study of algorithms of direct (〈em〉K〈/em〉 〉 1)-rank modification of the ALF parameters. These algorithms attain the said objective omitting the 〈em〉K〈/em〉-fold application of known rank-one (〈em〉K〈/em〉 = 1) modification algorithms. We also synthesize a combined algorithm (CA) of (〈em〉K〈/em〉 ≥ 1)-rank modification of the ALF parameters that is more computationally simple and more numerically robust compared to known algorithms. The ALF employing the CA can serve as an effective tool for solving various tasks of space-time adaptive signal processing in pulse radars of different purpose.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Ever growing demand for higher data rates requires appropriate radiation systems with large bandwidth and stable gain. Microstrip antennas with unidirectional radiation patterns and stable gain are most useful for this purpose. A ground plane defect of microstrip patch antenna is used to breed multiband applications. As a result, the performance of gain, directivity, and bandwidth is enhanced, the geometry and shape of an ultrawideband (UWB) antenna are simplified, and its size is reduced. Thus, it results in the efficient performance with respect to wideband operation. A novel band notching of microstrip truncated UWB antenna is implemented for insusceptibility in the range 5.2–5.8 GHz. The suggested structure contains circular truncated and T-shaped slots for band notching. The optimal results can be obtained by selecting the antenna parameters. Advantages of the proposed antenna include small size, better impedance match and simple design. Details of the suggested and observational solutions are demonstrated in this paper. The 〈em〉S〈/em〉〈sub〉11〈/sub〉 parameter of antenna is–45.5 dB at a resonant frequency of 4.6, 5.5, and 9.8 GHz. The gain of antenna is 5.47 dB, and the value of VSWR is smaller than 2, which makes the proposed structure an ideal choice for its application in wireless communication, 5G and IoT.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The errors of navigation satellite ephemerides are one of the key factors to determine the accuracy of satellite navigation. To improve the accuracy of ephemerides calculation, modern satellites are equipped with inter-satellite measurement equipment. However, random interference is inevitably present in the data transmission path and it is necessary to minimize its effect. To perform this task, it is proposed to use the stochastic estimation of ephemerides of navigation satellites that are moving along disturbed orbits in the form of a procedure of parametric optimization based on the minimization of the additive set of two functionals. The optimization of the first functional provides the minimum of uncertainty in the estimation of ephemerides. The optimization of the second functional provides the minimum of the norm of the vector of orbital parameters variations in the current time interval. To illustrate the effectiveness of the proposed approach, a numerical simulation of the satellite constellation’s ephemerides estimation was carried out for the corresponding trajectory perturbations. The simulation results illustrate the possibility to determine the ephemerides of navigation satellites with the accuracy within units of meters based on the approach considered that uses the noisy inter-satellite measurements.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Last years, most sub-Nyquist sampling and parameters estimation methods for linear frequency modulated (LFM) signals are based on compressed sensing (CS) theory. However, nearly all CS reconstruction algorithms are with high computational complexity and difficult to be implemented in hardware. In this paper, a novel framework of sub-Nyquist sampling and low-complexity parameters estimation for LFM signals is proposed. The incoherent sampling in CS theory is introduced into the construction of sub-Nyquist sampling system, but no CS reconstruction algorithm is employed in the estimation of parameters. Based on the energy aggregation of LFM signals in the proper fractional Fourier transform (FRFT) domain, the chirp rate and center frequency can be estimated by linear operations. Accordingly, the proposed estimation method is easily realized compared with existing estimation methods based on CS. Simulation results verify its effectiveness and accuracy.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A fully integrated cross-coupled charge pump circuit for boosting dc-to-dc converter applications with four-clock signals has been proposed. With the new clock scheme, this charge pump eliminates all of the reversion power loss and reduces the ripple voltage. In addition, the largest voltage differences between the terminals of all transistors do not exceed the power supply voltage for solving the gate-oxide overstress problem in the conventional charge pump circuits and enhancing the reliability. This proposed charge pump circuit does not require any extra level shifter; therefore, the power efficiency is increased. The proposed charge pump circuit has been simulated using Spectre in the TSMC 0.18 μm CMOS process. The simulation results show that the maximum voltage conversion efficiency of the new 3-stage cross-coupled circuit with an input voltage of 1.5Vis 99.8%. According to the comparison results of the conventional pump and the enhanced charge pump proposed, the output ripple voltage has been significantly reduced.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The potential efficiency of optimal interperiod processing (IPP) of coherent batch radio pulses reflected from point air targets against the background of high-power clutter is analyzed during the radar operation in the pulse-Doppler mode with middle frequency of probing at ambiguous measurements of target range and velocity. This efficiency is compared with IPP efficiency during the radar operation in the coherent pulse mode. The analysis is performed at constant and variable probing intervals when the time span of the clutter source zone is both less and greater than the probing interval in pulse-Doppler radar, i.e. in the absence and presence of superposition of clutter from different range sections. The cases of complete match of parameters of clutter superposition are analyzed at different radial velocities of equipotent clutter layers, and also the cases of superposition of nonequipotent clutter layers, the powers of which are inversely proportional to the squared distance from their sources. In addition, the wobbling of intervals of signal probing is also taken into account.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Devices for shaping and processing of signals based on known varieties of digital amplitude-phase modulation are considered. Their disadvantages are exposed during realization of modulation and demodulation of the signals that are characterized by non-rectangular signal constellations. There are explored properties of devices for shaping and processing of signals based on a new variety of signal modulation, namely amplitude modulation of many components (AMMC). The results of carried out researches show that advantages of proposed AMMC modulator are simplification of phase modulated or amplitude-phase modulated signal shaping, in particular AMMC signal shaping, and improve of modulator internal interference protection. Advantages of AMMC demodulator are simplification of phase modulated or amplitude-phase modulated signal processing, in particularAMMC signal processing, and improve of demodulator internal interference and zero drift protection at its practical realization. The proposed AMMC modulator and demodulator can be applied for shaping and processing of signals based on known and new varieties of amplitude-phase modulation.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Planar dielectric resonators (DR) with height significantly lower than the operating wavelength are investigated as a new class of disk dielectric resonators of the millimeter wavelength range with whispering gallery (WG) modes. It is known that in the open state, such resonators based on the WGmodes are not excited due to high radiation losses. It is shown that the solution of this problem is the partial shielding of the disk dielectric structures with a plane-parallel screen by placing the disk between two flat conducting mirrors. It has been established that by introducing an air gap between the flat base of the dielectric disk and one of the conductive mirrors, it is possible to increase the quality factor of the planar DR almost twice. One of the reasons for this is the partial displacement of the resonant field of the WG modes from the dielectric region to the air gap, where the dielectric losses are lower. In addition, an increase in the air gap in the range of optimal values, comparable to half the working wavelength, leads to a decrease in ohmic losses. The above causes an increase in the quality factor of planar DR as an air gap is extended.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Free-Space Optical (FSO) can provide high-speed communications when the effect of turbulence is not serious. However, Space-Time-Block-Code (STBC) is a good candidate to mitigate this seriousness. This paper proposes a hybrid of an Optical Code Division Multiple Access (OCDMA) and STBC in FSO communication for last mile solutions, where access to remote areas is complicated. The main weakness effecting a FSO link is the atmospheric turbulence. The feasibility of employing STBC in OCDMA is to mitigate these effects. The current work evaluates the Bit-Error-Rate (BER) performance of OCDMA operating under the scintillation effect, where this effect can be described by the gamma-gamma model. The most obvious finding to emerge from the analysis is that the BER can be enhanced by orders of magnitude for different numbers of users and different values of scintillation effects using a MIMO channel as compared to Single-Input-Single-Output (SISO) one. The theoretical analysis of the derived BER, which is based on gamma-gamma model, is validated through the Monte Carlo simulation.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Attenuators and phase shifters which are the circuits for amplitude-phase distribution control are key elements of antenna arrays. Dispersion of technology parameters results in deviation of the characteristics of integral circuits from rated values that requires application of the techniques for this effect compensation. In this paper there are considered the methods for development and calibration of the circuits in a basis of vector-sum signals allowing to modify both amplitude and phase of input high-frequency signal. It is proposed the method of calibration on a basis of interpolation of measured dependences of absolute value and phase of transfer factor on controlling voltage. Application of proposed method for calibration of vector phase shifter with operating frequency band 2.8–3.2 GHz fabricated with 0.18 μmCMOSallows to provide mean square deviation of phase error is not greater than 0.9°. At that amount of required measurements is 20 times decreased comparing known approach on a basis of measurement of all amplitude-phase states.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Antenna parameter optimization using S-shaped metamaterial embedded in antenna substrate is elucidated in this paper. Upon incorporation of proposed metamaterial array inside the antenna substrate, the bandwidth of antenna increases by 74% and directivity by about 11%. Results obtained are in good coherence when using the FEM based Ansoft HFSS simulation and MATLAB programming based on CAD formulas using the equivalent circuit analysis of patch antenna. The evolution of ‘S-shape’ has been explained beginning from the primitive Single Split Ring Resonator’s shape. The proposed structure was fabricated and nearly 6% deviation was obtained in comparison with the simulation results. This metamaterial antenna overcomes the low bandwidth limitation of patch antenna and helps in maintaining a low profile by obtaining 81% miniaturization.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A broadband patch antenna is presented with a modified rectangular patch containing three symmetrical slots and an asymmetrical slot. A U-slot is inserted into the ground plane, which enables a wide operational fractional bandwidth of 143% ranging 2.9–17.5 GHz. The modified rectangular patch offers acceptable omnidirectional radiation pattern at higher frequencies with radiation efficiency of 83 to 95%. The maximum achievable gain is 5.48 dBi across the entire bandwidth. The electromagnetic wave modeling is conducted using high frequency simulator structure (HFSS) and the circuit model is simulated with Advance Designing System (ADS) software. The housing effect is studied using vertical orientation of antenna to approximate its performance in the presence of conducting bodies. The proposed antenna architecture has small electrical dimension of 0.17×0.11λ. Simple configuration and wide bandwidth makes proposed patch antenna a suitable candidate for versatile communication applications.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉There are proposed signal-code constructions consisting of two or more components shaped on a basis of binary sequences with a property of multiplicative complementariness of their matched filtering results. There are considered systematically the rules of synthesis of such binary sequences containing signal-code constructions; there are described analytically their correlation properties, their processing specificities and the structure of obtained resulting signal. On a basis of statistical model of correlated signal components and their clusterization there is shown theoretical continuity of proposed signal-code constructions and Barker’s binary sequences. There are represented the examples of shaping, processing and parameters of researched signal-code constructions. It is carried out comparative analysis of structural specificities and noise immunity of multiplicative complementary signal-code constructions with complementary sequences (Golay’s codes), i.e. signal-code constructions with property of additive complementariness, there are exposed their advantages and drawbacks regarding spectral characteristics and signal detection characteristics (errors of the first and second genus).〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this paper there are researched regularizing properties of discretization in a space of output signals for some linear operator equation with noisy data. The essence of proposed method is selection of discretization level which is a parameter of the regularization in this context by the principle of equality of random and deterministic components of the input signal recovering error. It is shown the method, i.e. the solution which is discrete by input signal is stable to small inaccuracies in input signal. At that in case of definite level of output signal measurements inaccuracy the recovering error of input signal is unambiguously defined by input signal sampling increment that allows to select reasonably the regularization parameter for specific criterion, for example, for definite measurements inaccuracy. Specific calculations and examples are represented in explicit form for single-dimension case but this does not restricts generality of proposed method.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The paper proposes a method for enhancing the accuracy of estimation of frequency offset for OFDM modulation based communication systems. An increase accuracy of the proposed method is achieved at the expense of combined use of pilot and information symbols of OFDM signal. The main factors determining the accuracy of proposed method were identified. Mathematical simulation of the proposed method was performed for a multipath radio wave propagation channel. The proposed method efficiency was shown in comparison with existing methods for the estimation of frequency offset. Advantages and disadvantages of existing and proposed methods were described. The relationships of the root-mean-square error of frequency offset estimation as a function of the signal-to-noise ratio were built for the proposed and existing methods. The attainable high accuracy of frequency offset estimation by employing the proposed method makes its use expedient in control and measuring equipment. Conclusions have been made regarding the simulation results obtained and the expediency of proposed method applications.〈/p〉

Description: Design and construction peculiarities of multifrequency crystal oscillators technically invariant to temperature effects have been considered. The analysis of thermodynamic characteristics of multifrequency temperature-compensated crystal oscillators was performed in conditions of nonstationarity of the thermal behavior of piezoelectric resonator. The volume density of heat source was determined during the excitation of quartz crystal resonator. Thermodynamic processes occurring in multifrequency crystal oscillators were investigated at the stage of settling of quartz crystal resonator oscillations. The need of taking into account the thermodynamic component during the investigation of high-speed thermal processes taking place in quartz crystal resonators was proved. The efficiency of using a multifrequency-algorithmic approach for ensuring the invariance of piezoresonance devices was estimated. It was shown that the use of this approach makes it possible to essentially reduce the temperature instability of crystal oscillators and reduce the up time of these devices due to a more exact compensation of initial frequency drifts.

Description: This paper presents new design variants of third order multi-bit sigma delta modulator (SDM): low distortion SDM and cascaded SDM. The proposed modulator based on the conventional SDMsuch L-0MASH(Multi-stAge noise SHaping) and interstage feedback topology. TheMASHSDM is not a single loop system. One of the drawback is that performance is limited by uncancelled noise from the first modulator and interstage feedback topology only cancels nonlinear errors introducing by multi-bitDACin the final stage, but the rest stage still containsDACnonlinearity errors without any noise shaping which still degrade overall system performance. An improved version of cascaded multi-bit SDM is proposed to overcome these problems mentioned above. In addition a third order low distortion SDM is also proposed. Simulation results verify the superiority of the both proposed modulator.

Description: It is solved in closed form the problem of the uniform isotropic medium excitation with Heaviside step of magnetic field. There are represented calculation results of the medium field.

Description: The combined impact of active and passive interferences on coherent pulse radar was investigated. A mathematical model was developed implementing a new method for compensating the active component of combined interference in coherent pulse radar employing spectral differences in the structure of active and passive interferences. The results of simulation reveal that the polarization-time signal processing involving the use of rejection filters for suppression of passive interferences in circuits of forming the weight coefficients of automatic compensator make it possible to significantly enhance the quality of active interference compensation under conditions of exposure to combined interferences. The rejection of passive interference in circuits of forming the weight coefficients is shown to eliminate the distortion of passive spectrum distortion at the output of adaptive polarization filter.

Description: This paper describes the mathematical model, which allows to investigate both fluctuation and systematic errors of target angular coordinates measurement in a radar with planar phased antenna array under the influence of external sources of noise radiations. The results of mathematical simulations are presented.