Investigation of backscattering enhancement of waves propagation in random medium is a crucial factor in remote sensing. Medium effects on waves backscattering are important to measure the error rate in radar detection of targets with a finite size. In this paper, we present numerical results for the backscattering enhancement factor assuming different medium parameters and target configuration. Convex illumination region of partially convex surface is assumed. We consider targets to take large sizes of about five wavelengths and a plane wave incidence in the far field. Waves propagation and scattering from objects are calculated in free space and random medium while considering Epolarization of incident wave.

This paper provides the theoretical validation of the unconditional stability, using the Von Neumann method, for the radial point interpolation method (RPIM) and Crank-Nicolson (CN) scheme, in a three dimensional (3D) problem. Moreover, the matrix inversion process, typical of the CN implicit scheme, is circumvented and approximated by a finite series for a particular stability factor range. To validate numerically the efficiency of the CN-RPIM unconditional stability, the resonant frequency inside a 2D double ridged rectangular cavity is simulated. The numerical results confirm that the CN-RPIM is significantly efficient, since the simulation time is reduced by up to 90%, and the memory requirement is saved up to 81%, with a few loss of accuracy.

The work presents an inventive, simple and implementable design approach to enhance the bandwidth of conventional Salisbury Screen Microwave Absorber (SSMA). Theoretically, the maximum fractional bandwidth of SSMA for FR4 substrate with an optimum sheet resistivity of 308 Ω/sq for -10 dB reflection is nearly 42.1%. In comparison, the bandwidth for square patch based SSMA is 59.7% with the same thickness. The design comprises square patches of SSMA placed periodically on a metal sheet. The square patches consist of an FR4 substrate and a 200 Ω/sq resistive sheet. A single reflection null is observed in the SSMA due to λ/4 resonance whereas in the proposed absorber an additional resonant mode is introduced due to coupling between the nearby patches. The simultaneous overlapping of the λ/4 mode and the additional coupling mode results in bandwidth extension. The close agreement between the simulation and measurement data is observed.

High power density and torque capability are distinguished features of slotted axial flux permanent magnet machine. However, due to alternate placement of slot and teeth, the airgap permeance and airgap magnetic energy vary with angular position. Even in absence of current excitation, the magnetic variation with position results in cogging torque. This torque produces several undesirable phenomena such as mechanical vibration, acoustic noise, torque ripples, voltage ripples and speed ripple in machine performance. The severity is high for low speed, light load, and direct drive applications. Various design modifications such as slot skewing, magnet skewing, axillary slots, optimization of pole pitch to pole arc ratio and many more are reported for cogging torque mitigation. Any of these design modifications adversely affects the machine performance in terms of no load magnetic field distribution, linkage flux, and induced emf. In this paper, the effect of magnet skewing is investigated for dual-rotor permanent magnet axial flux machine. The analytical model is developed for the determination of magnetic field distribution at no load. Three different types of open slots stators viz. type 1: trapezoidal Slot with trapezoidal teeth, type 2: Parallel slot with trapezoidal teeth, and type 3: trapezoidal slot with parallel teeth are used for the investigation of air-gap magnetic field density and cogging torque produced in machine. The analytically obtained results are compared with finite element analysis (FEA) for the validation.

Statistical characteristics of scattered ordinary and extraordinary electromagnetic waves in the magnetized plasma are considered using the smooth perturbation method. Diffraction effects and polarization coefficients are taken into account. Second order statistical moments of scattered radiation are obtained for arbitrary correlation function of electron density fluctuations. The expressions of the broadening of the spatial power spectrum and displacement of its maximum are obtained. Wave structure functions and the angle of arrivals are calculated. Scintillation level of scattered radiation is analyzed for different parameters characterizing anisotropic plasma irregularities for the ionospheric F-region. Numerical calculations of the statistical characteristics are carried out for the three-dimensional spectral function containing anisotropic Gaussian and power-law spectral functions using the experimental data.

In this paper, we propose a novel compact switchable monopole CPW-fed antenna which has the ability to be used for narrowband as well as UWB applications. A single element antenna to be used for wireless local area network (WLAN) applications is first proposed in this article having overall dimensions of 24×30.5 mm². The corresponding antenna has been transformed to UWB frequency range just by utilizing two variable capacitors within the designed structure. The proposed small size, variable, low cost as well as low weight antenna with good propagation characteristics performs well in the WLAN as well as in the UWB frequency band. The proposed antennais simulated using Ansoft HFSS, and results are validated in CST Microwave Studio suite. The proposed antenna has also been fabricated, and the measured response is correlated with the simulated ones.

The paper presents the results of observing, in a real time, the process of combustion in air of aluminum nanopowder ignited by laser radiation. The obtained results convincingly evidence the possibility and perspective of visualization of ignition process by means of laser monitor. The video images allow observing the main stages of the combustion process including starting of combustion in the place of laser radiation focusing, spreading of the heat wave and appearance of the second combustion wave. For quantitative analysis of the combustion process, we suggest to analyze the average intensity of images registered by laser monitor.

A low phase noise reflection oscillator using a hexagonal substrate integrated waveguide (SIW) resonator is proposed in this paper. The hexagonal SIW resonator, which can combine flexibility of a rectangular cavity and performance of a circular cavity, is convenient for oscillator design. Since any of the six sides of a hexagonal resonator can be utilized for coupling, the oscillator configuration is flexible and adaptable. A simplified generalised phase noise condition and its optimization approach are proposed for the low-phase noise oscillator design. Furthermore, a 10.4 GHz oscillator prototype was designed, fabricated and measured to validate the proposed optimization approach. The measured results show that this oscillator provides 11.3 dBm output power and possesses low phase noise of -127.2 dBc/Hz at 1 MHz offset from 10.4 GHz carrier frequency, which is suitable for low-cost application in microwave and millimeter-wave band.

This paper presents a comprehensive analysis of a current-mode-logic frequency divider (CML FD) and the theoretical locking range of CML FD. The locking range of the CML divider is proportional to the injection ratio. By adding a resistive load, the locking range of the CML divider is not limited by the Q value of the LC resonant circuit. The minimum input power to drive the divider is achieved when the output frequency is equal to the self-oscillation frequency. To verify the properties of wideband and multi-phase outputs, the ÷4 octet-phase frequency divider based on a two-stage CML FD was implemented using a 0.18 μm CMOS process. It has a locking range of 1 GHz to 8 GHz with a 12.6 mW dc power consumption, and the phase deviation between the octet output signals is less than 4.7°. With an ultra-wide frequency bandwidth and accurate octet outputs, the proposed divider is suitable for multi-phase generator applications.

In this paper, the effect of corrosion on the magnetic behavior of a magnetic material used as a magnetic circuit in the induction machines is studied. With this objective, the magnetic properties of the samples with corrosion and without corrosion were evaluated by the study of hysteresis loops using a homemade vibrating sample magnetometer (VSM). The magnetic parameters extracted from the hysteresis loops such as saturation magnetization, coercive, remanent magnetization, squareness ratio, magnetic permeability, and hysteresis area were analyzed. It was shown that more energy is required to demagnetize the sample with corrosion than the sample without corrosion, and the hysteresis loss in the case of the sample with corrosion is more than the case of the sample without corrosion. These mean that when the corrosion is presented in the magnetic circuits of the induction machine, the hysteresis loss increases, consequentially reducing the machine efficiency.

In this paper, a compact dual-band MIMO antenna for WI-MAX and WLAN applications with improved isolation is proposed. The proposed design consists of two counter facing F shaped monopoles placed closely to each other with edge to edge spacing of 10 mm (0.1167λ₀ at 3.5 GHz). Each monopole element operates over 3.5 and 5.8 GHz bands. The isolation over the operating dual bands is achieved by using an elliptical slot and a rectangular parasitic strip. S₁₁ < -10 dB is achieved over 3.2-3.8 GHz and 5.7-6.2 GHz with S₁₂ < -20 dB. The overall dimension of the proposed antenna is 30 × 26 mm². The proposed antenna has correlation coefficient < 0.03, diversity gain > 9.8 dB with stable radiation pattern over the operating dual bands. The measured results are in good agreement with the simulated ones. The proposed antenna is a suitable candidate for MIMO applications.

A pair of broadband double-sided parallel-strip line (DSPSL) to coplanar waveguide (CPW) vertical transitions are presented. The transitions are composed of CPW open end with connected grounds forming two strips of the DSPSL with single via connection. The connected grounds of CPW, which forms top strip of the DSPSL are of two dierent shapes resulting in two transitions (Types 1 & 2). Simulated results for the back-to-back transitions, using the multilayer solver of CST Microwave Studio, show good agreement with the measured ones.

As a kind of complex targets, the non-rigid vibration of an aircraft as well as its attitude change and the rotation of its rotating parts will induce complex nonlinear modulation on its echo from low-resolution radars. If these nonlinear modulation features which reflect the physical characteristics of an aircraft target can be extracted effectively, then they are helpful to target classification and recognition. However, the echo translational component and background clutter have a very adverse effect on the extraction of such features. On basis of introducing the ensemble empirical mode decomposition (EEMD) algorithm, the paper firstly performs the decomposition of real recorded aircraft echo data from a low-resolution radar by EEMD and distinguishes the false component, body translational component and micro-motion component by calculating waveform entropy in the Doppler domain. Secondly, it carries out characteristic analysis and feature extraction further on the echo micro-motion component separated and extracts three features of the micro-motion component, including Doppler domain waveform entropy E_mc, normalized equivalent Doppler spectrum width BW₀, and normalized frequency interval between the adjacent maximum spectral peaks on both sides of the spectrum center Δf₀. The analysis results show that EEMD can be used to separate the body translational component and micromotion component of an aircraft echo effectively, and the proposed features (E_mc, BW₀ and Δf₀) can be used as effective features for aircraft target classification and recognition.

A modified three-way in-phase equal Gysel power divider/combiner (PDC) and a method for implementation this novel three-way Gysel PDC on plane structure are proposed in this article. To obtain accurate values of the line impedance,the derivation of the exact equations is based on even-odd mode analysis. An experimental prototype is realized. The results show that this three-way Gysel PDC has good matching, isolation and magnitude-phase balances with high power handling capabilities.

This paper presents a novel 2D meta-surface wall to increase the isolation between microstrip patch radiators in an antenna array that is operating in the teraherz (THz) band of 139-141 GHz for applications including communications, medical and security screening systems. The meta-surface unit-cell comprises conjoined twin `Y-shape' microstrip structures, which are inter-digitally interleaved together to create the meta-surface wall. The proposed meta-surface wall is free of via holes and defected ground-plane hence easing its fabrication. The meta-surface wall is inserted tightly between the radiating elements to reduce surface wave mutual coupling. For best isolation performance the wall is oriented orthogonal to the patch antennas. The antenna array exhibits a gain of 9.0 dBi with high isolation level of less than -63 dB between transmit and receive antennas in the specified THz-band. The proposed technique achieves mutual coupling suppression of more than 10 dB over a much wider frequency bandwidth (2 GHz) than achieved to date. With the proposed technique the edge-to-edge gap between the transmit and receive patch antennas can be reduced to 2.5 mm. Dimensions of the transmit and receive patch antennas are 5×5 mm² with ground-plane size of 9×4.25 mm² when being constructed on a conventional lossy substrate with thickness of 1.6 mm.

This paper presents a CPW-fed UWB band-notched antenna having continuously tunable WiMAX rejection band and fixed WLAN rejection band. As the WLAN frequency band is fixed all over the world, it is made fixed with the use of a newly designed resonator in the radiating patch. As the main problem is that the WiMAX band is different in different countries of the world, between 3 and 4 GHz, it is made continuously tunable by using a novel miniaturized implemented resonator in the partial ground plane with variable capacitors. Altering the values of these capacitors tunes the 3-4 GHz rejection band continuously.

Design and experimental optimization of a 5 cm-diameter electron cyclotron resonance (ECR) Ion Thruster was carried out. The experimental results with the shorten discharge chamber demonstrated that its maximum efficiency, specific impulse, and thrust were 38%, 4300 s, 2.3 mN with the power of 130 W, respectively. The beam current was increased with the increment of the propellant flow rate and screen grid voltage. In addition, the performance of the thruster was associated with the distance of the antenna and screen grid. However, the optimum distance depended on the input microwave power which was about 20 W.

The rapid quantification method of human serum glucose was established by using the Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR). Based on the optimal predicting effect, a subtraction band model combining with optimal single continuous wave band was developed. The spectrum (1600-900 cm^-1) was selected as the base band. Then, window subtracted partial least squares (WSPLS) based on the spectrum was carried out, and the optimal two continuous bands were found. The results show that the prediction effect of the base band model is obviously better than that of the whole spectral model, and WSPLS model is even better than base band model. Finally, an independent test set was tested for model verification. V-SEP and V-R_P were 0.831 mmol/L and 0.882, respectively by the compensation model.

Objective: In this paper we present a study of a novel method to noninvasively monitor temperature noninvasively during thermotherapy, for instance, in cancer treatment using M-sequence radar technology. The main objective is to investigate the temperature dependence of reflectivity in UWB radar signal in gelatine phantoms using electrically small antennas. Methods: The phantom was locally heated up, and consequently changes of signal reflectivity were observed. Results: An approximate linear relationship between temperature change and reflectivity variations was formulated. To show the potential of this approach we used an M-sequence MIMO radar system. The system was tested on breast-shape phantom with local heating by circulating water of controlled temperature. For two dimensional imaging the Delay and Sum algorithm was implemented for two-dimensional imaging. Significance: The article is a study of temperature measurement using UWB radar system for possible usage in thermotherapy.

In this work, a wide-angle and wide-band transmission-type circular polarizer based on a bi-layer anisotropic metasurface is proposed, in which the unit cell consists of two layers of identical patterned metal films deposited on the two sides of a homogeneous dielectric layer, and the geometric pattern of the metal film is a square aperture surrounding a concentric square-corner-truncated square patch. The simulated results show that the polarizer can realize a linear-to-circular polarization conversion at both x- and y-polarized incidences in the frequency range from 7.63 to 11.13 GHz with a relative bandwidth of 37.3%, and it can maintain a stable polarization conversion performance under large-range incidence angles. Moreover, it has no asymmetric transmission effect, and the transmission coefficients at x- and y-polarized incidences are completely equal. Finally, one experiment is carried out, and the simulated and measured results are almost in agreement with each other.