Light-Controlled Polarization of MM-Waves with Photo-Excited Gratings in a Resonant Semiconductor Slab

We investigated photoconductive gratings in the resonant semiconductor layers as light-controlled polarizers for the millimeter (MM) waves. We compared the effects of strip-like, wire-like, and fin-like gratings excited by the red light and the IR radiation in Silicon wafers, respectively. The fin-like gratings are shown to be the preferred structures that can operate at the limited light intensity. The light-sensitive shift of maxima of transmitted power and polarizing efficiency towards the lower frequency band is observed. The effect makes photoconductive gratings and similar patterns potentially suitable for the design of light-controlled frequency-tuning and frequency-modulating components of resonant quasi-optical devices

Wavelet Based Denoising of the Simulated Chest Wall Motion Detected by SFCW Radar

Low power and compact radars have emerged with the development of electronic technology. This has enabled the use of radars in indoor environments and the realization of many applications. The detection, tracking and classification of human movements by radar are among the remarkable applications. Contactless detection of human vital signs improves the quality of life of patients being kept under observation and facilitates the work of experts. In this study, it was simulated that the movement of the chest wall was modeled and detected by the SFCW radar. Gaussian, Rician and uniformly distributed random noise types were added to the modeled chest motion at different levels. The noisy signal obtained at the receiver is denoised with different mother wavelet functions and the performances of these functions are presented comparatively

A Novel Augmented Railgun Using Permanent Magnets

A novel augmented railgun using a permanent magnet is proposed in this paper. The effects of the permanent magnet on the magnetic field and distribution of current density have been investigated. High current densities in the railguns can lead to high local temperature and erosion of the rails. Therefore, the current densities in the rails and armature should be decreased without the reduction of the Lorentz force which is required for acceleration. For this purpose, augmentation of the magnetic field can be used as an effective method. The Finite Element Method (FEM) simulations have been applied in this article to analyze the performance of the railgun in the presence of the magnets. Two augmented railgun structures have been introduced to produce a constant external magnetic field. For both structures, augmented railgun characteristics are studied in comparison to the railgun without the augmentation. The results show that augmentation with permanent magnet increases railgun efficiency, especially in low current railguns. For pulse current source I=30kA, Lorentz force of the augmented railgun with four magnets is 2.02 times greater than the conventional railgun

The Effect of Error Propagation on the Performance of Polar Codes Utilizing Successive Cancellation Decoding Algorithm

 In this paper, we discuss and analyze the effect of error propagation on the performance polar codes decoded using the successive cancellation algorithm. We show that error propagation due to erroneous bit decision is a catastrophic issue for the successive cancellation decoding of polar codes. Even a wrong decision on a single bit may cause an abundance of successor bits to be wrongly decoded. Furthermore, we observe that the performance of polar codes is significantly improved if even single bit errors are detected and corrected before the decoding of successor bits

High Gain Circularly Polarized Pentagonal Microstrip for Massive MIMO Base Station

In this paper we propose a circularly polarized pentagonal microstrip antenna on a suspended substrate with coaxial probe feed and five loaded slits for Massive MIMO BS Antenna applications. Massive Multiple-Input Multiple-Output (MIMO) is one of the key component to be incorporated in the 5G cellular systems. The proposed antenna is successfully simulated using HFSS 13.0, fabricated on a FR-4 substrate and measured. The proposed antenna exhibits a much higher gain of 6.17dB, improved impedance bandwidth of 171.9 MHz (Return loss, S11= -10dB) , axial ratio bandwidth (< 3dB) of 135 MHz , patch area of 1775 mm2  , and also yields return loss better than -15 dB around the center frequency of 2.45 GHz (ISM Band). Measured characteristics of the antenna are in good agreement with the simulated results

Design of a Polarization-Independent Dual-Band Electromagnetically Induced Transparency-Like Metamaterial

In this study, the classical analog of single and dual-band electromagnetically induced transparency is demonstrated with a four-fold symmetric metamaterial consisting of a Minkowski fractal ring resonator surrounded by a square ring resonator. The proposed metamaterials show high transmission ratios at the polarization independent resonances, as confirmed by the applied two different numerical methods. Delay-bandwidth products are found to be 0.34 and 0.61 at the resonances of the dual-band metamaterial. The peak frequencies and transmission ratios maintain also for oblique angle of incidences. These features of the proposed metamaterials are promising for single and multi-band filtering applications as well as for slow light and sensing devices

Composite Material Characterization using Eddy Current by 3D FEM Associated with Iterative Technique

In this paper, an iterative technique, employing the T formulation associated with the finite element method, based on Maxwell's equations and the Biot-savart law, is used for analyzing the density of eddy currents in composite carbon fiber reinforced polymer (CFRP) materials. For this purpose, a code has been developed for solving an electromagnetic 3D non-destructive evaluation problem. This latter permits the characterization of this CFRP and determinate of fibers orientation using the impedance variation which is implanted in polar diagram. Firstly, the obtained results are compared with those of the analytical model. This comparison reveals a high concordance which proves the validity of the proposed method. Secondly, three different applications are shown for illustrating the characterization of unidirectional, bidirectional and multidirectional piece using a rectangular coil plotted in normalized impedance diagram

The Prototype of a Wideband Ku-Band Conical Corrugated Horn Antenna with 3-D Printing Technology

This study is about the design and production of a conical corrugated horn antenna used to feed reflector antennas in satellite communication (direct broadcast satellite-DBS) systems. The antenna designed with CST Microwave Studio program operates within wideband of 10.5-18.5 GHz at Ku-band. The prototype is realized with new generation 3D printing technology and conductive paint coating method, which makes the antenna lightweight and provides low cost and faster production. According to measurement results, the antenna has return loss almost better than 20 dB, gain value of minimum 14.5 dBi and sidelobe level of -18 dB at most within 1.76:1 frequency bandwidth. Antenna is observed to have a gain loss of at most 1.5-2 dB within the band as compared to the same antenna with high conductivity metal, which needs higher cost and production time for the manufacturing

Lightning Response of Multi-Port Grids Buried in Dispersive Soils: An Approximation versus Full-wave Methods and Experiment

In this paper, application of multi-conductor transmission line model (MTL) in transient analysis of grounding grids buried in soils with frequency-dependent electrical parameters (dispersive soil) is investigated. In this modeling approach, each set of parallel conductors in the grounding grid is considered as a multi-conductor transmission line (MTL). Then, a two-port network for each set of parallel conductors in the grid is then defined. Finally, the two-port networks are interconnected depending upon the pattern of connections in the grid and its representative equations are then reduced. Via solving these simplified equations, the transient analyses of grounding grids is efficiently carried out. With the aim of validity, a number of examples previously published in literature are selected. The comparison of simulation results based on the MTL shows good agreement with numerical and experimental results. Moreover, in despite of numerical methods computational efficiency is considerably increased

Above-light-line Nonlinear Surface Polaritons near a Conductive Interface: Threshold Case

We investigate the TM-polarized nonlinear surface polaritons (NLSP) propagating along aguided structure consisting of a magnetic optically linear medium and a non-magnetic opticallynonlinear medium with saturable permittivity separated by a flat conductive layer of zerothickness. We consider those values of hosting media bulk material parameters for which theNLSP existence (for zero sheet conductance) has threshold character with respect to the wavesintensity. Based on the exact solution of Maxwell's equations we show that the energy andpropagation properties of the NLSP near the above-light-line condition (1 > n > 0) dependconsiderably on the surface conductivity of the layer, even the threshold character of the NLSPcan be lost; for certain sheet conductance values these waves can exist in a linear limit. TheNLSP propagation constant is defined by both the surface conductivity and field intensity andcan be varied in a wide diapason, which gives an opportunity to obtain and control the importantfor quantum information processing 0 n condition. For a chosen value of the NLSPpropagation constant the NLSP field intensity and energy flux decries when the surfaceconductivity grows; saturation of the nonlinear permittivity leads to an increase of the NLSPenergy flux compared with Kerr-like nonlinearity