The paper describes a novel low profile circularly polarized antenna. The antenna is a single dipole over a particular wire formed panel with high impedance properties. Although the principles of operation for the antenna are general, in this work they are specifically applied to the design and optimization of a FM broadcasting antenna. The distinguishing feature of the design is that it incorporates the following interesting concepts simultaneously: artificial high impedance surfaces or artificial magnetic conductors, materials showing refractive indexes of less than unity (n < 1), and polarizing structures. Another advantageous aspect of the design is the computational efficiency emerging from this fact that the structure is entirely wire made. This way the relevant numerical analysis and optimization can be efficiently carried out by NEC, a one-dimensional (1D) MoM-based EM analyzer.

This paper presents an efficient meshless approach for solving electrostatic problems. This novel approach is based on combination of radial basis functions-based meshless unsymmetric collocation method with projection domain decomposition method. Under this new method, we just need to solve a Steklov-Poincare interface equation and the original problem is solved by computing a series of independent sub-problems. An electrostatic problem is used as an example to illustrate the application of the proposed approach. Numerical results that demonstrate the accuracy and efficiency of the method are stated.

This paper proposes two methods for increasing the Gain of Vlasov Antenna. The first method, using a Parabolic Cylinder Reflector, results in a 7dB increase in the Gain. The second method, constructing a Horn on the aperture, increases the Gain by about 5dB. The results were checked using a prototype antenna and there was a close agreement.

Abstract-Radiation characteristics of a probe-excited rectangular ring antenna are investigated by using the dyadic Green function approach. The radiation characteristics, such as radiation pattern, beam-peak direction, half-power beamwidth and directivity, are analyzed. For the specified operating frequency, the ring width and ring height are selected as the same crosssectional dimension of rectangular waveguide operated at the dominant mode. The effects of the excited probe and rectangular ring to the modal distributions are described. For the desired modal distribution, the directivity primarily depends on the ring lengths. For compact size of the proposed antenna, the ring length of 0.4λ is chosen to provide a bidirectional pattern with the calculated half-power beamwidth in E-plane and H-plane of 100 and 69 degrees respectively, and directivity of 4.43 dBi. Furthermore, the prototype antenna was fabricated and measured. The coincided results between the theory and the experiment are obtained.

This paper presents a new method to counter Anti Radiation Missiles (ARM) threats, which is effective against advanced ARM. By using random phase and amplitude active decoys in the specified optimum positions and network implementation we show that the ARM threats will be removed dramatically. Also, iterative methods are presented to cancel the internal interference effects in the proposed structure.

Time Reversal Mirror (TRM) technique, in the virtue of its high resolution in the heterogeneous media, has been widely applied in the area of acoustics and electromagnetics. In this paper, the technique is developed to imaging targets in the contest of ultra-wideband (UWB) through wall radar (TWR) through numerical simulation. We firstly consider the technique to image targets behind a single-layered wall and then extend to the multi-layered wall. The simulation results have reported the imaging capability of the algorithm and its powerful use for TWRimaging. For concerning the image stability, we investigate the TRM images for the case in which there is a mismatch between the walls associated with the forward and inverse phases of time reversal. The back projection imaging algorithm is compared here at the same time for a contrast of the imaging quality. Finally, some conclusions are drawn.

This paper links the polarization-sensitive-array signal detection problem to quadrilinear decomposition model. Exploiting this link, it generates a deterministic blind quadrilinear decomposition-based signal detection algorithm, which doesn't require DOA (direction of arrival) and polarization information and has blind and robust characteristics. The proposed algorithm fully utilizes the polarization, spatial and temporal diversity. The simulation results reveal that the performance of blind quadrilinear decomposition-based signal detection algorithm for polarization sensitive uniform square array is close to nonblind MMSE method, and even works better than trilinear decomposition algorithm.

A comparison between two recently developed methods for antenna diagnostics is presented. On one hand, the Spherical Wave Expansion-to-Plane Wave Expansion (SWE-PWE), based on the relationship between spherical and planar wave modes. On the other hand, the Sources Reconstruction Method (SRM), based on the application of the equivalence principle and the integral equations relating fields and sources. In order to compare the results provided by these methods, a reflector antenna has been measured and analyzed.

In this paper the discontinuity problems of the junction of two different dielectric rectangular waveguides has been studied, both for two dimensional (2D) and three dimensional (3D) cases. The technique used, is to obtain expressions for the z-directed complex power due to all modes (propagating and non propagating) present at the step junction for a normalized incident field. The expressions for junction parameters like admittance and susceptance have been derived for the structures with step junctions in x direction, in y direction and for the 3D case where the step is both x and y directed. The numerical results have then been computed for different step ratios of these three cases.

An efficient iterative method is presented for the fast analysis of cylindrically conformal microstrip structures. Based on the transmission line modeling (TLM) method and the fast modal transform (FMT) theory, this technique accelerates the process of the calculation by introducing the concept of the transverse electromagnetic waves instead of the transverse fields considered in the traditional algorithm. Within cylindrically stratified media, the transverse electromagnetic waves are represented by the hybrid modal basis functions. Ultimately, the specific form of the modal admittance and the spectral reflection matrix are deduced. Further more?the surface electric fields and electric currents of the cylindrically conformal microstrip antenna fed by means of a microstripline are calculated via the iterative process. On this basis, the input impedance of the antenna can also be obtained. And the results gained by utilizing iterative approach are compared with those from the published references to demonstrate the accuracy or efficiency of this method.

A well known property of large circular closed-loop arrays is that when the dimensions and the distance of the cylindrical dipoles are properly chosen, the arrays possess very narrow resonances. As far as single isolated loop arrays are concerned, the phenomenon has been predicted and analyzed in the past in the framework of ``two-term" theory. In the present paper the same methodology is, for the first time, applied to investigate the system of two coupled identical circular arrays. It is found that the spectral profile of this new array is characterized by the coupling-induced splitting of the resonances of the single loop array into symmetric and antisymmetric supermodes, in direct analogy with other types of coupled electromagnetic cavities. Due to the circular symmetry of the individual arrays, the phenomenon is strongly correlated to the optical counterpart of two coupled traveling-wave optical resonators, such as whispering gallery or microring resonators. By borrowing the resonance splitting model from optical resonators, this analogy connection is investigated and interesting conclusions are reached.

This paper presents a dispersive finite difference time domain (FDTD) method suitable for the analysis of electromagnetic field rotator (and cloaking) devices. The method employs a coordinate transformation which accurately accounts for the radial dependence of the permittivity and permeability tensors, with Drude material models applied to the respective diagonal elements. The key aspect of the present formulation is the inclusion of the radial dependence of the plasma frequency, which makes this formalism quite attractive for the modeling of a general class of cloaking and field rotator geometries. Firstly, the method is validated by comparing its results with a previously published simulation of a cloaking device. Then, it is applied for the first time to the analysis of dispersive effects on the performance of field rotators.

In this paper, a statistical approach to evaluate randomly rough surfaces (RRS) in an inverse scattering problem is presented. Whereas in these investigations the roughness criterions possess random variables, the use of deterministic techniques such as the target decomposition (TD) can not be useful by itself as a tool of analysis. In these conditions, a statistical approach is essentially required to evaluate the target parameters. The goal of this study is the estimation of the polarimetric signatures, such as the scattering mechanism α and the entropy H, via a novel approach including the combination of TD and a new statistical model. To validate our work, SAR data sets, provided by the European Space Agency (ESA), are analyzed and compared with the simulation results.

We describe an experimental set-up for exposure of small animals to radiofrequency standing waves that allows direct measurement of the power absorbed by the animal. Essentially, the set-up consists of a metallic box containing an antenna and experimental animal immobilized in a methacrylate holder; a signal generator feeding the antenna; and a power meter. In addition, the box can also contain a video camera to record the animal's behaviour, and a receiving antenna (connected externally to a power meter and a spectrum analyser) to detect alien radiation and harmonics. The absorbed power measurement trivially allows calculation of whole-body mean SAR from the animal's weight; and assuming local SARs to be proportional to whole-body mean SAR, the latter can be used to adjust organ-specific SAR predictions obtained by simulation using a commercial FDTD program with a numerical phantom. The use of the system is illustrated by application to rats given subconvulsive doses of picrotoxin to induce a seizure-prone state analogous to epilepsy: levels of the neuronal activity marker c-Fos in the frontal and piriform cortex of picrotoxin-treated rats exposed to 900 MHz GSM radiation were twice as high as those of unexposed animals.

In this paper, a high performance phased antenna array is designed. Compared with the traditional ones, this antenna array has a lower sidelobe characteristic of down to -16 dB. At different scanning angles, the comparison between calculated and measured results of S-parameters and E- and H-plane antenna patterns is made and a very good agreement is found. Moreover, the precorrected fast Fourier transform method is employed to accelerate the entire computational process to reduce significantly both the memory requirement and computational time, but to increase the design accuracy and optimization efficiency.

Multicarrier Phase-Coded signals have been recently introduced to achieve high range resolution in radar systems. As in single carrier phase coded radars, the conventional method for compression of these signals is based on using matched filter or direct computation of autocorrelation function. In this paper we propose a new method based on Discrete Fourier Transform (DFT) that has lower computational complexity compared to the conventional approach. It has been proved that the proposed method is mathematically equivalent to matched filtering, so there is no processing loss. Also the effect of sampling frequency on compression loss has been investigated and for the oversampled matched filter of MCPC signals, a computational efficient algorithm based on polyphase implementation has been proposed.

A novel transition structure based on Substrate Integrated Circular Cavity (SICC) is proposed in this paper. The design approach has been developed for transition designing in other operating frequency. Good performance of flexibility and S-parameters were observed for the new transition structure. Different design tools were used to validate the design method.

In this paper, a novel structure for Ka-band micro electromechanical switches with low actuation voltage is proposed. In this structure, the membrane of the switch is chosen to be a Koch fractal. We have analyzed these switches in order to extract their parameters such as insertion loss, return loss and deformation posture. The effect of the actuation voltage on the deformation of the bridge has been analyzed and the results are compared with simple rectangular bridges. It is shown that bias voltage of these kinds of switches is remarkably lower than that of its other counterparts. This switch may be used as a low loss and effective element for more complicated systems such as distributed phase shifters and phased arrays.