Радиотехника и электроника

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A New Invariant to Illumination Feature Descriptor for Pattern Recognition

Sat, 12/01/2018 - 00:00

Abstract—A new descriptor for describing features in gray-scale images that is invariant to nonuniform illumination is proposed. The suggested method for the feature descriptor design is based on a local energy model which is a biologically plausible model of the visual system. The algorithm for feature detection and construction of the descriptor uses the scale-space monogenic signal framework and a modified algorithm for calculation of the histogram of oriented gradients based on the phase congruence of the signals. The results of computer simulation show that the proposed descriptor provides excellent detection and matching of features at nonuniform illumination, noise, and minor geometric distortions in comparison with known descriptors.

Uniform Reflection from a Plasmonic Metasurface

Sat, 12/01/2018 - 00:00

Abstract—Reflection of electromagnetic waves from a plasmonic metasurface consisting of a periodic array of grooves in a metallic layer has been investigated. It is shown that, at certain parameters of the system, the amplitude and phase of the reflected s-polarized wave do not depend on the angle of incidence and the dependence of the reflection coefficient on the angle of wave incidence is suppressed by the excited groove plasmon polariton. It is demonstrated that such a uniform reflection can be used to create a grooved parabolic reflector; in particular, it better levels the wave front from a source placed at the focus as compared to the case of an ungrooved parabolic reflector.

On AUV Navigation Based on Acoustic Sensing of the Seabed Profile

Sat, 12/01/2018 - 00:00

Abstract—A method for determining the current position of an autonomous underwater vehicle (AUV) based on an algorithm for determining the AUV velocity using acoustic sensing of the seabed profile is proposed. The method uses velocity measurement as an additional sensor of the absolute velocity whose data are shared with the inertial navigation system (INS) as the input data of a filter determining the AUV position.

Design and Analysis of Complimentary Split Ring Resonator Backed Microstrip Transmission Line Using Equivalent Circuit Model

Sat, 12/01/2018 - 00:00
Abstract

This article presents a compact, low-profile Band-Stop Filter (BSF) designed using Complimentary Split Ring Resonator (CSRR). An equivalent circuit model is also presented along with the simplified mathematical approach to extract the parameters of the circuit model. This paper also presents the effect of variation in the dimensions of split rings on characteristics of BSF. The proposed BSF has a compact size of 27 × 20 mm2 designed an FR-4 substrate with dielectric constant ( \({{\varepsilon }_{r}}\) ) 4.3. The filter provides complete suppression of the band at 2.4 GHz. The design and circuit analysis of this metamaterial based filter is presented in terms of reflection coefficient, transmission coefficient and impedance curve.

Compact CoPlanar Waveguide-fed Ultra Wide Band and Band Switchable Slot Antenna for Cognitive Radio Front-end System

Sat, 12/01/2018 - 00:00
Abstract

A compact coplanar waveguide (CPW)-fed ultra-wideband (UWB) slot antenna with four narrowband switchable states is presented in this paper. Cognitive Radio (CR) portable devices demand a compact antenna. In planar monopole antennas where a large space around the patch is getting wasted that can effectively be used in UWB slot antennas. The proposed antenna consists of a half-elliptical slot radiator fed through a half-elliptical shaped tuning stub to operate in the UWB mode for CR sensing. However narrowband antenna is required to operate in CR communication purpose. To operate in the narrowband mode the UWB slot antenna is fed through a defected ground structure (DGS) integrated CPW line. Frequency re-configurability is achieved by changing the DGS slot length using eight PIN diode switches. The proposed compact antenna can cover UWB frequency range from 3.14 GHz to 12 GHz. It has omnidirectional radiation pattern and also has high realized gain which is especially suited for CR front-end applications.

Voltage Differencing Transconductance Amplifier-Based Quadrature Oscillator and Biquadratic Filter Realization with All Grounded Passive Elements

Sat, 12/01/2018 - 00:00
Abstract

The work realizes the sinusoidal quadrature oscillator and biquadratic filter with the same configuration using merely two voltage differencing transconductance amplifiers (VDTAs) as active devices and one grounded resistor and two grounded capacitor as passive elements. Performing the quadrature oscillator, the realized circuit is capable of producing two quadrature voltage outputs with almost equal amplitudes, and an independent electronic control of oscillation condition and oscillation frequency. Operating in voltage-mode biquadratic filter, the circuit can simultaneously generate the bandpass and lowpass filtering functions without any matching constraints. The natural angular frequency and the quality factor of the filter are independently and electronically adjustable. The effects of the VDTA non-idealities are also investigated in detail. Simulation results with TSMC 0.25 μm CMOS technology validate both working functions of the proposed circuit.

Fast Non-Local Mean Filter Algorithm Based on Recursive Calculation of Similarity Weights

Sat, 12/01/2018 - 00:00

Abstract—A theoretically derived technique for acceleration of the original non-local means image denoising algorithm based on calculation of recursive patch similarity weights is proposed. A significant amount of computation in the non-local means scheme is dedicated to estimation of the patch similarity between pixel neighborhoods. The proposed recursive weights calculation scheme adopts the classic recursive mean calculation scheme for a multidimensional shift-vector in order to lower the computational complexity of the original non-local means method, thus speeding up this algorithm more than tenfold. Note that the output of the proposed algorithm is exactly the same as that of the original non-local means method. Hence this algorithm belongs to the class of true fast algorithms, unlike methods approaching to a certain degree the resul of the original algorithm.

Fast Recursive Computation of Composite Correlation Filters

Sat, 12/01/2018 - 00:00

Abstract—Algorithms for tracking multiple objects using correlation filters require calculation of a composite filter based on synthetic discriminant functions in order to increase the robustness to changes in posture, partial overlapping of objects by other objects, scaling, rotation, nonuniform illumination, and complex background. The calculation algorithm has large computational complexity. In this paper, we propose recursive calculation of a composite filter using algorithms for rapid inversion of matrices to accelerate synthesis of the filter. Computer simulation results on calculation of a composite correlation filter are presented and discussed in terms of the computation accuracy and the rate of calculation.

Volume Magnetostatic Spin Waves in 3D Ferromagnetic Structures

Sat, 12/01/2018 - 00:00
Abstract

Propagation of volume spin magnetostatic waves in meander-shaped ferromagnetic films with vertically and horizontally coupled segments is studied. Conditions under which forward and backward volume magnetostatic waves simultaneously exist in the films are determined. Micromagnetic simulation and expansion in terms of plane waves are used to calculate internal effective magnetic fields and dispersion characteristics of the waves in such structures. Spectra of coupled waves in meander-shaped vertically coupled ferromagnetic films are studied. Prospects for application of the above structures in the development of magnonic elements are analyzed.

Predictive Multi-user Dynamic Spectrum Allocation Using Hidden Semi-Markov Model

Sat, 12/01/2018 - 00:00
Abstract

For wideband Cognitive Radio (CR) devices, the availability of primary user (PU) activity prediction model can save sensing energy and time, track spectrum variations, reduce switching overhead, improve spectrum usage and lower interference to PU. Using Universal Software Radio Peripheral (USRP) generated data, this paper has verified the superiority of Hidden Semi-Markov model (HSMM) over the conventional HMM in learning and predicting temporal correlations in PU spectral activity under non-geometric distribution of state durations. Numerical simulations further show that in a coordinated multi-SU/PU scenario, compared to the traditional random Carrier Sense Multiple Access (CSMA), the proposed HSMM-dynamic spectrum allocation (DSA) protocol significantly reduces aggregate interference to PU. Depending on the number of SU, there exists a trade-off between “interference-free coexistence with PU” and “self-existence of a large number of SU”. This problem is addressed further by statistically modeling probability of free channels and using it to optimize the number of SU that can be allocated. The proposed scheme outperforms the conventional sensing based dynamic spectrum allocation (DSA) in terms of reduced PU interference, lower spectrum handoff requirements and higher spectrum utilization efficiency. The predictive optimized HSMM-DSA can be used as an additional layer of intelligence for any CR device for efficient spectrum sharing.

Dual-Band High Selective Frequency Selective Surface Design and Analysis

Sat, 12/01/2018 - 00:00
Abstract

In this paper, a second-order, dual-band, band-pass frequency selective surface (FSS) with high selectivity is presented by cascading three-layers of periodic metallic arrays. The unit cell in both two exterior layers is composed of gridded-double square loops (G-DSLs) while the element in the middle layer is consisting of wire grid. The three layers are separated by two thin F4B-2 substrates with dielectric constant of 2.65 + 0.02i. The proposed FSS can provide multi-transmission poles and multi-transmission zeros. There are two transmission poles in each pass-band. The two pass-bands are separated by two transmission zeros. On the upper side of the second pass-band, other two transmission zeros are generated also. These transmission zeros lead to a wide out of band rejection and a fast fall off response on both sides of each pass-band. The simulation is implemented using full wave electromagnetic simulator CST Microwave Studio, the central frequencies of the two pass-bands are 12.7 and 17.4 GHz. In addition, the designed principle is described using equivalent circuit model (ECM). Furthermore, the prototype of the FSS is fabricated and measured. Both simulated and measured results demonstrated that the proposed FSS has the merits of incident angle stability from 0° to 60° for both TE and TM polarizations.

Tracking the Optimal Sequence of Predictive Strategies

Sat, 12/01/2018 - 00:00
Abstract

Within the prediction (decision making) theory with online experts, an adaptive algorithm is proposed that aggregates the decisions of expert strategies and incurs losses that do not exceed (up to a certain value, called a regret) the losses of the best combination of experts distributed over the prediction interval. The algorithm develops the Mixing Past Posteriors method and the AdaHedge algorithm of exponential weighting of expert decisions using an adaptive learning parameter. An estimate of the regret of the proposed algorithm is obtained. The approach proposed does not make assumptions about the nature of the data source and the limits of experts’ losses. The results of numerical experiments on mixing expert solutions using the proposed algorithm under conditions of high volatility of experts’ losses are given.

Near-Infrared Luminescence of Bismuth in Silica-Based Glasses with Different Additives

Sat, 12/01/2018 - 00:00
Abstract

The near-infrared (NIR) luminescence spectra and changes caused in them by an exposure to ArF excimer laser radiation were studied in bismuth-doped silica-based glasses containing Al, P or Ge and B additives. Experiments were conducted using specimens in the form of optical waveguides synthesized by surface plasma chemical vapor deposition (SPCVD), using bismuth-doped glass sample as the light-guiding core. Excited by ~808, ~904, and ~970 nm wavelength laser diodes, the NIR luminescence spectra were recorded in the 700–2000 nm wavelength range at temperatures of 105 and 300 K. The UV laser treatment was found to cause changes in both integrated intensity and spectrum shape of NIR luminescence associated with bismuth impurities. The observed changes are discussed with the assumption of photo-induced reconfiguring of different bismuth inclusions, which might present in the glass network in the form of separate ions and atoms, interstitial molecules, and bulk semiconductor nanoclusters.

Compact Penta Band Notched Antenna Using Concentric Rings with Splitter Bricks for Ultra Wide Band Applications

Sat, 12/01/2018 - 00:00
Abstract

In this paper novel miniature ultra wide band circular mono pole antenna with penta band rejection characteristics is proposed. The antenna is fed through a Coplanar Waveguide (CPW) feed. The antenna is designed using RT/ DUROID substrate with permittivity 2.2. In the proposed antenna Concentric Rings with Splitter Bricks (CRSB) are used to achieve band notching characteristics. It will reject the existing WIMAX (Worldwide Interoperability for Microwave Access) from 3.326–3.612 GHz, C band down link frequency from 3.8–4.2 GHz, WLAN application from 5.393–5.822 GHz, X Band downlink Satellite communication application from 7.25–7.733 GHz and ITU band operations from 8.0–8.565 GHz. The Simulations of this antenna are carried out using CST microwave studio suite 2016. Antenna performance parameters like Return loss, Voltage standing wave ratio (VSWR), Radiation efficiency and Gain are evaluated. Radiation pattern of the antenna at different frequencies are observed. This antenna provides good gain and a larger band width over the frequency range 3.1–11.6 GHz.

Optimal Control of Data Transmission over a Fluctuating Channel with Unknown State

Sat, 12/01/2018 - 00:00

Abstract—Optimization problem for data packet transmission over a communication channel governed by a hidden Markov process is considered. The transmitter is modeled as a single-channel finite-buffer queuing system with non-stationary Poisson arrivals. The service rate is proportional to the controlled transmission rate with channel-dependent factor. Buffer overflow leads to packet losses, whereas channel state worsening results in lower service rate. The goal of the optimization problem is to minimize average losses under constraint on the transmitter energy consumption. The exact form of the optimal policy is presented for the augmented control problem. Several control policies with incomplete information are proposed on the basis of the optimal control and hidden state estimates. We consider two estimates based on the optimal filtering equations and the current queue state. Results of computer simulation are presented to compare the control policies under consideration.

Synthesis of an Adaptive Detector in the Spectral Domain

Sat, 12/01/2018 - 00:00
Abstract

A method for signal detection via estimation of the noise power in the spectral domain is proposed. The influence of the probability density function of the parameter estimate on the result of operation of the detector under the conditions of prior uncertainty is analyzed. Dependences of the parameter distribution in the case of its known estimate are obtained by the example of the additive Gaussian noise. The results of simulation of detector operation with and without consideration for the influence of the distribution of the parameter estimate are presented.

Features of Dispersion Characteristics of Surface Spin Waves in Coupled Antiferromagnetic Films with Easy-Axis Anisotropy

Sat, 12/01/2018 - 00:00
Abstract

Propagation of magnetostatic spin waves in a layered structure consisting of two vertically coupled via a nonmagnetic dielectric layer antiferromagnetic (AFM) films has been studied. The results of calculation of the dispersion dependence for the AFM films with an easy-axis anisotropy are presented. It has been shown that splitting of coupled modes occurs in the region of AFM resonance frequencies. The behavior of coupled modes as a function of the parameter of coupling between films has been studied.

Design and Implementation of Fractional Order Differintegrators Using Reduced s to z Transforms

Sat, 12/01/2018 - 00:00
Abstract

The Design and implementation of fractional order digital differentiators and integrators is the main objective of this paper. Identify the novel reduced s to z transforms calculated using model order reduction techniques. Thus the transforms are discretized directly using Continued Fraction Expansion (CFE).The designed differentiators and integrators are implemented on Xilinx Spartan 3E field programmable gate arrays (FPGA) and are tested using the sinusoidal, square and triangular waveforms. The practical results agree with the theoretical ones.

Coexistence of Wi-Fi and LTE-LAA Networks: Open Issues

Sat, 12/01/2018 - 00:00

Abstract—An increase in the network capacity is a requirement for modern LTE cellular networks. A part of the RF spectrum that is available for transmission is among the most important limiting factors. Such a problem can be solved in the LTE networks using unlicensed bands that are employed in alternative (e.g., Wi-Fi) technologies with the aid of a new LTE-LAA technology. In this work, we perform a comparative analysis of the channel access procedures for unlicensed bands that are described in the Wi-Fi standard and LTE-LAA specification and discuss open problems of coexisting technologies.

A Model of Forecasting of Information Events on the Basis of the Solution of a Boundary Value Problem for Systems with Memory and Self-Organization

Sat, 12/01/2018 - 00:00

Abstract—One of the problems in forecasting of news events is the development of models that allow working with a weakly structured information space of text documents. A distinctive feature of such a news space is the stochastic nature of the processes in it, the presence of memory, and the possibility of self-organization of information. It is interesting to develop a model for predicting events on the basis of a stochastic dynamics of the changing of images (or the state of the information space) of news clusters with allowance for memory and self-organization. The article discusses the schemes of transition probabilities between states in the information space, on the basis of which a nonlinear second-order differential equation is derived and a boundary value problem for predicting news events is formulated and solved. The analysis of the model described in the article shows the possibility of an increase in the probability of reaching the predicted event almost immediately after the beginning of the process of changing the structure of news clusters and the presence of abrupt jumps and oscillations in the probability of reaching an event.

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