A miniaturized planar nonbianisotropic left‐handed metamaterial

In this article, a miniaturized nonbianisotropic left‐handed metamaterial composed of spiral‐S‐shaped resonator and conducting wire is proposed. This symmetrical structure avoids bianisotropy and it shows a controllable low‐loss double negative (DNG) band. Its electrical size is less than half of the well‐known S‐shaped resonator, which makes it to be considered as a good homogenous effective media. Although the structure is not uniplanar, it is not vulnerable to fabrication errors stem from misalignment of both sides. Both the simulation and experiment results demonstrate left‐handed properties. Also, a circuit model is proposed which can accurately predict the magnetic resonant frequency. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Miniaturized resonant inclusions as non-bianisotropic double negative metamaterials for normal incidence

Two novel resonators were devised which are amendments on commonly used S-shaped resonator and enable a great miniaturization rate. The symmetrical structure of these inclusions can avoid magnetoelectric coupling in the artificial constituents that preclude the bianisotropy. One of these metamaterials is an integration of continuous wire and an S-shaped-spiral. The other is a structure of SRRs and S-shape resonator with improved electromagnetic coupling and reduced electrical size. Both of them have wide negative refraction passband with low losses. The superior performances of these structures were investigated numerically and experimentally for only normal incidence case and tested through a proper comparison with the S-shaped resonator.     

Fast adjustable spectrum sensing circuit for cognitive radio applications

A fast and adjustable spectrum sensing method is proposed using a phase frequency detector for cognitive radio applications. Using this method, spectral sensing can be done in a very short time by a low‐cost, low‐power circuit, compared with available implemented methods. Different aspects of sensing procedure in different situations are investigated including frequency sweep time and system errors. Accurate operation of this method is verified through simulations, and comparison with other methods shows faster sweep rates. Copyright © 2013 John Wiley & Sons, Ltd.     

Admittance of an isolated waveguide-fed slot radiating betweenbaffles using a spectrum of two-dimensional solutions

An efficient method of computing resonant length and admittance characteristics of an isolated broad-wall shunt slot radiating between baffles of finite height is presented. The outer three-dimensional (3D) field problem associated with this geometry is reduced to a two-dimensional (2D) one via a Fourier transformation with respect to the longitudinal z direction. For each value of the longitudinal wave number k_z an integral equation is solved for the E field in the mouth of the plates using the method of moments. This procedure is repeated for several discrete values of k_z, to obtain a spectrum of 2D solutions which are then inverse-transformed to construct the 3D solution in the spatial domain for the exterior baffle region and the half space. The slot aperture field is determined by the conventional moment method solution to the integral equation that enforces the continuity of the H field across the slot. Scattering properties of the slot are then deduced. Numerical results for the resonant length and resonant conductance are presented. Computer results are found to be in good agreement with experimentally measured data