Abstract In this article, a novel semi-blind channel estimation scheme for Multiple-Input Multiple-Output (MIMO) communication system is studied and implemented for quasi-static Rayleigh fading channel, in which channel matrix H remains relatively constant throughout the block. Channel matrix H can be decomposed as a rotation matrix Q and down triangular matrix R. The triangular matrix R is estimated

Abstract This paper presents a compact fractal antenna operating in the frequency range of 3.1–10.6 GHz that is designed, simulated and tested for UWB application. In the present days, the broadband wireless technology gained popularity due to its large bandwidth, high data rate and low complexity. In 2002 the Federal Communication Commission (FCC) allocated a frequency band of 3.1–10.6 GHz (UWB) for

Abstract The paper deals with a dual wide band micro-strip line fed compact antenna consisting of wide circular slot. The proposed antenna is designed on FR-4 dielectric material having εr = 4.3. The antenna is fed by 50 Ω microstrip line and the optimized volumetric dimension of the proposed antenna is 36×36×1.6 mm3. A wide circular slot is cut from the ground plane resulting in dual nature of antenna

Abstract This study considers a new measure of distortions of speaker speech sounds that is invariant with respect to the gain of speech signal in a communication channel. Properties of the measure are investigated in comparison with its closest analogues. A series of theoretical features has been proved. The new measure is shown to combine advantages of the symmetric Itakura distance in relation to

Abstract The influence of temperature and ionized radiation on the properties of current stabilizers, based on JFETs with p–n-junction as a gate and MOSFETs in saturation mode at two-pole connecting when the gate and source are closed, is experimentally investigated. It is shown that current temperature coefficient of the JFET is negative, and the one of the second type is positive. Connecting a stabilizing

Abstract The reconstruction of tomograms in magnetic resonance imaging (MRI) has been considered for different degrees of transverse gradient instability of magnetic field. A method for minimizing the impact of deviation of resultant points of signal measurements from regular positions on the quality of reconstructed tomograms was proposed. The ultimate values of parameters of field gradient instability

Abstract This paper presents S11 measurements of a flat, slotted, sub-mm sized antenna, integrated with a Schottky diode; the overall structure being termed a ‘multenna’ in description of its action to radiate a signal beam field that is a higher order harmonic of the signal beam field it receives. The multenna is constituted of two square slots; one tuned to receive at the frequency of 100 GHz and

Abstract Results of experiments on the use of three antenna units of ultra-wideband ground penetrating radars (UWB GPR) for nondestructive testing are presented. These three units have both different values of the centres frequency of the probing UWB pulses and different antenna configurations. The purpose of the performed experiments was to find the best values of sensing parameters. Another task

Abstract In this research we present the measured path loss values in typical urban and suburban areas at the operating frequency of 3.5 GHz. The measurements are carried out using the spectrum analyzer FSH6 in order to record the channel response. The values of path loss exponent n are calculated for urban and suburban environments. We also compare and analyze the path loss predictions with the measured

Abstract It is shown that fourth standardized moment (kurtosis) and its some functional transformations (inverse value, square root of inverse value) can be objective measures of clipping and quality of speech and music signals. The essential advantages of suggested measures are no need for previous estimation of probability density of analyzed signal as well as no need for information about undistorted

Abstract A compact dual-band dual-mode and dual-polarized (DBDMDP) antenna based on an asymmetrical Y-shaped microstrip line feeding along with a square ring radiator is proposed. The structure is loaded with two pairs of L-strips to extend the lower mode bandwidth (center frequency fc = 9.36 GHz). This section is employed to change an electromagnetic field distribution and achieve dipole-like omni-directional

Abstract This study is devoted to the substantiation of practical recommendations on the selection of parameters for the band-diagonal regularization of maximum likelihood estimates of Hermitian correlation matrices of Gaussian interferences. These parameters include the diagonal regularization parameter and band regularization parameter, which represents the compensation multiplicity, i.e., the number

Abstract The paper presents the results of analysis of signal and noise characteristics of autodynes with frequency modulation. The mathematical model of autodyne is presented in the form of a self-oscillator with single-loop oscillation system that is frequency-tuned using the varicap. This model takes into account the impact of intrinsic radiation reflected from location object and the impact of

Abstract In this paper, we present novel semi-blind channel estimation schemes for Rayleigh fading Multi-Input Multi-Output (MIMO) channel. Here channel matrix H is decomposed as an upper triangular matrix R, which can be estimated blindly using the Householder transformation based QR decomposition of received output covariance matrix and Q matrix, which can be estimated using the Tikhonov regularization-based

Abstract With the rapid growth of P2P network, the resource searching and resource delivery are two crucial problems required to be solved in a P2P system. At the resource searching stage, a large number of random resource requests form a search request queue at the node. At the resource delivery stage, if the nodes cannot process new requests at a certain time, the queue of resource requests may be

Abstract This paper proposes an approximate analytical and numerical constructive synthesis method of optimal waveguide polarizers based on three irises in square waveguide. A mathematical model of polarizer has been developed on the basis of waveguide transmission and scattering matrices. The analytical expressions derived for elements of the scattering matrix were used for determining the electrical

Abstract A new method of interpolation/approximation of univariate functions using exponential polynomials, both complete and reduced, generally using complex polynomials, was suggested. The solution is based on the Z-transformation of one variable function, predetermined by a discrete set of equally spaced samples. For the first time, the problem was solved for dynamic systems with proper frequencies

Abstract This paper is devoted to the description of mathematical models of cross-correlated and uncorrelated Gaussian direct-noise jamming with uniform frequency spectrum produced by spatially-point external sources of noise radiation. They are designed for airspace control radars with spatially narrow-band linear equidistant phased antenna array (PAA) consisting of identical omnidirectional elements

Abstract A compact dual-band circularly polarized (CP) printed antenna with microstrip line feed is studied in this paper. It consists of an inverted y-shaped radiator with an edge ground plane on the opposite side of the substrate. The edge ground plane plays important role in impedance bandwidth (IBW) enhancement. In order to enhance the axial ratio bandwidth (ARBW) by a significant amount, the dimensions

Abstract The presence of a large number of cell phone towers on the roofs of buildings inside cities raises several questions about whether the radiated electromagnetic frequency (EMF) and power spectrum density (PSD) affect the population even if the towers were installed based on the exiting conditions and standards in the cities. This paper aims to answer all these ambiguous questions by measuring

Abstract The paper proposes new methods of parametric and structural-parametric synthesis of resonators that contain multiple transmission line segments of the same length. These methods allow to optimize resonators of different configurations and with different characteristic impedances of line segments Z0i. Optimal resonators are those that have the minimum ratio m = Z0max/Z0min for a given ratio

Abstract Meeting emission masks set by regulation authorities is a typical task demanded of the pulse shaper. In particular, the release of the FFC emission masks for ultra-wideband (UWB) devices for the short-range and high data rate, stimulated research in designing pulse shaping techniques capable of closely approximating the mask, that is, the maximum possible transmit power under FCC limits to

Abstract Fifth Generation (5G) communication networks support multiple radio access technologies, popularly known as multi-RAT, to facilitate services to all the mobile subscribers irrespective of their subscription for any old generation network. Unique interleaver assignment to each active mobile subscriber within intra-RAT communication is comparatively easy task. However, the same becomes a challenging

Abstract This paper proposes a solution of the electrodynamic problem of determining the generalized scattering matrix of infinitely thin asymmetric one-sided inductive diaphragm in rectangular waveguide using the integral equation method. The problem is reduced to solving the system of integral equations in terms of the number of incident modes falling on the inhomogeneity from the left partial region

Abstract This paper presents a compact CPW-fed MIMO antenna for UWB applications. The four-element CPW-fed antenna is designed as a radiator. The isolations between the same polarized elements and the orthogonally polarized elements are more than 20 and 25 dB, respectively. The floating parasitic element is used to improve isolation at a higher frequency. The simulated and measured 10 dB impedance

Abstract The development results of new waveguide planar filters with high selectivity are presented in this article. New bandpass filters (BPF) based on folded metal structures have poles of attenuation characteristics near the filter passband and they are focused on selectivity improvement. Filters are designed in a fully symmetrical topology, which improves performance reproducibility, manufacturability

Abstract Massive advances in microelectronic manufacturing technology with an exponential growth of their complexity and speed are needed to ensure a continuous development of novel techniques, structures, devices, circuits and systems. This paper is intended for the introduction of a new PMOS transient model for modern microelectronic devices that provides a fast transient response. Such suggested

Abstract Underground working in different horizons with intricate haulage and traveling roadways is very complex in nature. Wired communication is presently the most adopted technology in Indian underground mines. Also, the cellular network cannot be used for communication due to the non-availability of the coverage link. So, addressing of key-personnel to pass on the information and assign task becomes

Abstract This paper presents a low noise amplifier (LNA) for the ultra-wideband (UWB) application in the range 3.1–10.6 GHz based on active inductor topology. The LNA is designed to provide a flat gain and to reject wireless local area networking interference at 5–6 GHz band. An active inductor based on the feedback resistor topology is proposed in this work and integrated with the LNA. The use of

Abstract A mathematical model of the signal formation process at the output of acousto-optic delay line (AODL) with direct detection has been proposed. This model is used to derive an equation of the AODL transient response. This equation is used to derive a formula for the pulse response characteristic that is utilized to determine the AODL voltage frequency transfer factor. The exponential notation

Abstract Climate change has become a phenomenon of global concern and it has resultant effect on the variability of radio propagation. In recent times, the issue of climate change has been a global phenomenon having its resultant effect on the variability of radio propagation. High-capacity radio signal fades due to absorption by atmospheric gases and scattering by hydrometeors which limits the link

Abstract The paper considers features of the Doppler velocity spectrum width of meteorological formations obtained on the basis of the pulse-pair method when a velocity Doppler spectrum differs from the Gaussian shape. Since the autoregressive models of various orders are widely used in practice for approximating the echo signals from meteorological formations and taking into account their spectrum

Abstract A waveguide planar bandpass filter for 2-cm wavelength range (13.5–14.5 GHz) with an ultra-wide stopband (up to the 6th harmonic of the central frequency of the bandwidth) is proposed, developed and experimentally investigated in this article. The filter with a bandwidth is designed on the basis of the antipodal fin-line (AFL) with an extremely high overlap of ridges, which has an overlap

Abstract The paper presents results of the development and performance optimization of 8-channel directional coupler (DC) of orthogonal type H21 modes in a circular multimode waveguide. This DC is designed for a high precision autotracking quasi-monopulse system of low-orbiting satellites for Earth remote probing. The design and testing of a prototype operating in the X-band 8–8.5 GHz were developed

Abstract An approximation method for the cumulative distribution function (CDF) of a signal envelope at the output of an arbitrary radio channel based on the gamma distribution is proposed. The well-known Nakagami approximation method is a special case of the proposed approach. In contrast to the Nakagami method, the convergence of the CDF of some arbitrary non-negative statistics to the proposed asymptotic

Abstract This paper presents a new ultrawideband omnidirectional microwave biconical antenna having gain above 10 dB that has been proposed, developed, optimized and experimentally tested. The main feature of the developed biconical antenna is its possible use in uniaxial dual-band systems of omnidirectional radio monitoring. The possibility of arranging two omnidirectional antennas having different

Abstract A laser heterodyne system for recording of small shifts and vibrations of remote objects is presented. The use of additional compensation interferometer makes it possible to compensate the influence of environmental fluctuations on the measurement results. The registration results of seismic vibrations for various setup configuration are shown. The experiments indicate the reducing of perturbations

Abstract Radar surveillance of unmanned aerial vehicles (UAVs) is actively developing area of scientific research. This article provides a review and analysis of publications in recent years devoted to the methods and radar systems of detection and recognition of classes and types of UAVs. It is noted that the most difficult targets for radar detection are low-sized, low-speed small UAVs (drones) flying

Abstract It is developed a method of information transmission with application of amplitude Single Sideband Hartley modulation (SSBH) allowing to increase of radio channel length for optical and fiber optic signal transmission systems where single sideband amplitude modulation (SSB) is used. Increase of communication range is provided due to application a sum of two orthogonal oscillations of the same

Abstract We consider the integrated circuit design and the measurement results of test crystals for the 12-bit sigma-delta analog-to-digital converter (ADC) based on 180 nm silicon-on-insulator (SOI) technology from X-FAB. The ADC processes input signals in the frequency range up to 100 kHz in the temperature range of –40…+175 °C with the supply voltage equal to 3.3 V and the modulator clock frequency

Abstract One of the possible physical mechanisms of so-called “angel” echoes, not visually observed radar discrete reflections from objects, is considered. The vortex flows can be the cause of “angel” echoes. They take out some volume of air with certain radiophysical parameters into the region of space with other radiophysical parameters of the air. Toroidal vortices (vortex rings) have a fairly long

Abstract This study proposes an approach for building high quality cheap emitters in mid-wave (MW) and long-wave (LW) infrared spectrum bands. A photonic infrared-wave emitter based on light down conversion from the region of fundamental absorption by semiconductor to infrared region has been proposed. The efficiency of such conversion does not depend on quantum yield of interband recombination. It

Abstract In this paper electromagnetic field energy balance equation for linear homogeneous dispersive stationary medium is deduced in general form. No dispersive limitations on ε′, ε″, μ′, and μ″ are used. Thus the following question is answered: why do existing equations not provide correct values for accumulated energy and dissipated energy in dispersive media? An electromagnetic field energy balance

Abstract The review of algorithms of estimation of stochastic processes with random structure and Markov switch obtained on a basis of mathematic tool of mixed Markov processes in discrete time is represented. It is shown that Markov property including continuous valued process with random structure in discrete time and Markov chain controlling its structure modification. There are considered recurrent

Abstract Conventional narrowband beamforming methods are not effective for wideband antenna arrays. Radiation pattern of such array has various beam width over the frequency. Existing frequency-invariant beamforming methods using finite impulse response filters (FIR-filters) can solve this problem. FIR-filters provide frequency response required for frequency-independent properties of the array radiation

Abstract The phenomenon of the voice signal acoustic variability in automatic speech recognition systems is considered. There are two varieties—intra- and inter-speaker speech variability. The probabilistic cluster model of minimal speech units in the Kullback–Leibler information metric is used for their mathematical description and comparison in magnitude. On its basis, theoretical estimates of the

Abstract Mostly random and adjacent error correcting codes are used to protect stored data in SRAMs against multiple bit upsets (MBUs). These MBUs caused by radiation are an important issue related to the reliability of static random access memories (SRAMs). As a result, multiple adjacent bits of a memory are distorted and valuable information is lost. To mitigate these problems, multi-bit adjacent

Abstract In this paper, three time-varying channel equalization schemes are studied in the underwater acoustic (UWA) Orthogonal Frequency Division Multiplexing (OFDM) communication system. The equalization algorithms are the zero-forcing (ZF) equalization algorithm, and the minimum mean square error equalization (MMSE) algorithm and the serial interference cancellation (SIC) equalization algorithm

Abstract Changes in the geometric parameters of ring coils, which are an essential element of transducer design used for non-destructive testing of ferromagnetic metals, entail a change in the self-induction coefficient (inductance) of alternating magnetic field source. In the article, on the basis of proposed approach [1], the equations for determining the ring coils inductance are obtained, allowing

Discrete cosine transforms are widely used in smart radioelectronic systems for processing and analysis of incoming information. The popularity of using these transform is explained by the presence of fast algorithms that minimize the computational and hardware complexity of their implementation. Type-IV discrete cosine transform occupies a special place in the list of the specified transformations

The research approach on the investigation of recombination parameters of nonequilibrium charge carriers in Si technological plates by thermal imaging method is offered in this paper. The lifetime, diffusion length and surface recombination velocity of charge carriers are taken into account. The method is based on a study of the spatial distribution of Si samples thermal radiation beyond the self-absorption

There is represented an information about phase inverters with split load. It is noted the problem of provision of identity of different polar signals at split loads. There are mentioned the specificities of Bragg’s diffraction in context of shaping of two different polar signals. It is shown that in case of modification of the frequency of electric signal at the input of acousto-optic modulator the

The paper presents the results for estimating the potential coding efficiency of spectrum envelope waveform (SEW) of speech signals (SS) by using the linear prediction (LP) method and using different sets of alternative equivalent parameters (AEP) that include line spectral pairs/projections (LSP), line spectral frequencies (LSF), and alternative line spectral parameters of highest splitting (LSP-HS

Abstract Mathematical expectations and variances of estimates of skewness and kurtosis coefficients of the noise signal model have been derived in this study. The specified noise signals represent the Bunimovich–Rice processes with exponentially power waveform of pulses expressed in terms of cumulant coefficients of the specified processes. It is shown that the distribution of instantaneous values

Image processing algorithms for compensation of the scattered radiation influence in X-ray imaging are proposed, studied and optimized by numerical simulation. These algorithms include the scattering estimation by convolution (superposition) technique, estimation of kernel functions by Monte Carlo (MC) simulation, the determination of the optimal number and shape of kernel functions and image segmentation

Abstract The independence estimation results of synchronously recorded pulse signals in distal parts of human radial arteries are presented in this paper. The study is carried out by the methods of structural-functional and simulation modeling in approximation of an equivalent planar movement of the biological object structural elements. Their elastic characteristics are taken into account using by

The ambiguity diagram of rectangular chirp RF pulse has been analyzed. The characteristic point of ambiguity diagram was identified. It was proposed to identify the signal on the basis of correlation level at the characteristic point of ellipsoidal ambiguity diagram built in a special coordinate system. The quasi-optimal autocorrelation algorithm with quadrature processing is proposed. This algorithm

The optimal and quasi-optimal algorithms of two-stage joint estimation of information symbols and frequency response (FR) of multibeam channels in OFDM-based communication systems have been synthesized. They involve the calculation of a posteriori probability density of estimated processes. At the first stage, the recurrent calculation of joint a posteriori distributions of information symbols and

The paper presents a method for calculating the radiation patterns (RP) of dual-reflector antenna systems taking into account the electrodynamic interaction between reflectors. This method is suitable for use in the resonance range of wavelengths with respect to the main dimensions of reflectors. The method is based on the iteration procedure proposed by the authors. Each iteration involves the use

Abstract A compact quad-band circularly polarized (CP) G-shaped printed antenna with square slot is proposed in this paper. Two semicircular notches have been etched from lower periphery of the ground to increase the impedance bandwidth (IBW). In order to increase significantly the axial ratio bandwidth (ARBW), a spring-shaped notch is etched from the upper periphery of the ground. For further increase