Band-stop Type Research Articles

Easy-to-Design-and-Manufacture Frequency Selective Surfaces for Conformal Applications

A bendable frequency selective surface (FSS) is proposed in this letter; it is based on short carbon fibers embedded into an epoxy resin whose characteristics are set in order to provide the required mechanical flexibility. The frequency response of the FSS is of band-stop type due to the half-wavelength resonance of the used short dipoles. The FSS design and the manufacturing process are clearly highlighted to demonstrate the advantages of the proposed FSS in terms of costs, ease to design and build the FSS, and accuracy of the obtained stopband response. Both aluminum and carbon materials are considered for the fiber as a mean for achieving a mechanically reinforced structure; the effects of both materials from an electromagnetic propagation point of view are discussed. Finally, the proposed FSSs with different fiber materials and bending radii are manufactured and experimentally tested in a free-space setup to verify the design. The proposed FSS is mainly suitable for applications on parabolic reflectors and curved radomes.

Analysis of finite frequency selective surfaces backed by dielectric substrate using sub-entire-domain basis function method

Purpose – Analysis of the frequency selective surface (FSS) is of great significance. In the method of moments, when the electric size of the FSS increases, huge in-core memory and CPU time are required. The purpose of this paper is to efficiently analyze the finite FSS backed by dielectric substrate utilizing sub-entire-domain (SED) basis function method. Design/methodology/approach – Different types of SED basis functions are generated according to the locations of the cells in the entire structure, and a reduced system is constructed and solved. The couplings of all cells of the FSS are taken into account by using Green’s function and Galerkin’s test procedure. The spatial Green’s function is obtained with the discrete complex image method. The reflection and transmission coefficients of the FSS are calculated using the far field of the FSS and the metallic plate with the same size. Findings – Moderate problems of the finite FSS backed by dielectric substrate are solved with the SED basis function method. The original problem can be simplified to two smaller problems. It enables a significant reduction to the matrix size and storage, and efficient analysis of FSS can be performed. The band-stop type of FSS can be composed of periodic conductive patch cells on the dielectric substrate, and shows total reflection property at the resonant frequency. Originality/value – The SED basis function method is mostly used to analyze periodic PEC structures in free space. The layered medium Green’s function is successfully employed and several dielectric substrate backed finite FSSs are discussed in this paper. The calculation of reflection and transmission coefficients, which are more effective rather than far field scattering of the FSS, are described.

Comparative Performance Analysis of Hamming, Hanning and Blackman Window

In the emerging field of medical image processing, computer vision, pattern recognition and other digital signal processing applications, window technique is vastly used. A window function is a mathematical function that is zero-valued outside of some chosen interval. When another function is multiplied by a window function, the product is also zero-valued outside the interval. In this paper, the performance of Hamming, Hanning and Blackman window have been mainly compared considering their magnitude response, phase response, equivalent noise bandwidth, sidelobe transition width, response in time and frequency domain using MATLAB simulation. To observe the responses, a FIR filter of low pass, high pass, band pass and band stop type have been designed and encountered them with each parameters stated above. The results that have been found is as same as its to be as stated in the theory. Comparing simulation results of different window, this paper has found Blackman window with best performance among them which is also expected from the theory. These windows have also been encountered with speech signal using MATLAB simulation and found the same expected result.

Microstrip Filter Designing by SRR Metamaterial

In this paper planar and compact band stop filter using split ring resonator (SRR) metamaterial is proposed. Band stop type attenuation is presented from L-to X-band. Low insertion loss in the pass band and high attenuation in the stop band can be considered as the advantage of this filter. Filter characteristics of SRR is presented using microstrip line. Here SRR is introduced in the substrate layer of microstrip line. It has been observed that the rejection level of the filter in stop band goes on increasing as we increase the number of SRR in the structure. Size of SRR is much less than the operating wavelength thereby several SRR can be introduced in substrate layer to provide a compact structure with high rejection level in the stop band. The frequency of filtering depends on the dimensions of SRR. The effect of varying the dimensions of SRR on the filtering frequency is also presented in this paper. It has also been observed by Nicolson-Ross-Weir approach that at the filtering frequency, value of relative permeability as well as relative permittivity for this structure is negative. This confirms that this structure behaves as a Left Handed medium.

Verification on Equivalent Circuit Model of Band-stop Type of Self-injection Locked NRD Guide Gunn Oscillator at 60GHz

Verification on Equivalent Circuit Model of Band-stop Type of Self-injection Locked NRD Guide Gunn Oscillator at 60GHz