Abstract-In this paper, the applications of chiral layers and metamaterials as radar absorbing materials are investigated. A perfect electric conductor plate covered by a chiral metamaterial is considered and after the formulation of the problem, reflection of the structure under an oblique plane wave incidence of arbitrary polarization is investigated. Then several examples of the applications of chiral layers in nondispersive, dispersive, and chiral nihility conditions are provided to design of zero reflection coatings. Finally, application of chiral metamaterial structures as microwave absorbers is discussed. In some of the provided examples, the method of genetic algorithm is used to optimize chiral coatings for the minimization of co-and cross reflected power.

In this paper, a rectangular metallic monopole antenna with normal rectangular stubs is presented for application in ultra wideband communication systems. It is shown by computer simulations (HFSS and CST) and actual fabrication and measurement that the addition of protruding normal metallic stubs leads to the increase of impedance bandwidth. The optimum design of geometrical dimensions of the antenna (consisting of the monopole plate and stubs) achieves up to 10 dB return loss in the UWB (3.1-10.6 GHz) frequency range. The radiation efficiency of antenna is better than 95%. Furthermore, the antenna provides linear polarization, with quite low cross-polarization levels.

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Regarding the increasing application of trahertz (THz) technology, the interest in using two-wire waveguides is getting more and more popular due to their favorable propagation properties. Therefore, a more accurate analysis of these structures is very important. In this paper, a simple analysis of the guided waves in a two-wire waveguide based on Bipolar Coordinate System (BCS) has been investigated. The structure under study is two infinite, perfect electric conductor (PEC) cylinders in z direction, whose axes are positioned at a distance d from each other. The solution of TE and TM modes is sought by the aid of electromagnetic formulation, and an analytical expression is proposed for electromagnetic fields and cutoff wavenumbers, which have not been present in any of the previous studies. In this study, for the first time a BCS is used to formulate two-wire waveguide problem, and the validity range of the answer is discussed. The values of the cutoff wavenumbers are calculated for the first few modes of TE and TM, using both the proposed method and Finite Difference Method (FDM). The precise correspondence of the obtained values with the proposed method with those of FDM, along with the high speed and simplicity in implementation, introduces the present method as an appropriate candidate for analyzing transmission lines using parallel cylinders.

Combining traveling-wave ring resonators and microstrip inductors in a planar microstrip line circuit, negative values of electric permittivity and magnetic permeability can be obtained. This phenomenon arises from negative permeability of the traveling-wave ring resonators and negative permittivity due to the behavior of shorted stubs within the rejected frequency band. Thanks to the nonreciprocal behavior of the travelingwave ring resonators we can achieve 16 dB isolation between s21 and s12 in the left-handed region. Therefore, a novel approach is presented here to synthesize a nonreciprocal magnetless lefthanded media in microstrip technology. Full wave simulation results confirm the left-handed behavior of the interaction. The concept can be extended to active nonreciprocal network.