SPATIAL FILTERS FOR LINEARLY POLARIZED ANTENNAS USING FREE STANDING FREQUENCY SELECTIVE SURFACE

Abstract

Free standing planar frequency selective surfaces (FSSs) are studied when utilized as spatial filters for linearly polarized antennas. The antenna spatial filter investigated in the present work is constructed up as a finite planar array of conducting strip dipoles. The electric field integral equation (EFIE) technique with the Rao-WiltonGlison (RWG) basis functions are used to get the current distribution on the conducting strips. The current distribution and backscattered electric field due to an incident plane wave are calculated and compared to some published work. The effect of polarization on the scattered field, and the frequency response of the spatial filter are studied. To test the operation of the proposed planar FSS, a bowtie antenna is used with the FSS employed as a spatial filter. The field transmitted by the antenna and passed over a wide frequency band through the FSS is calculated. It is shown that such a free standing planar FSS can operate as a band stop filter for linearly polarized antennas. It is also shown that even when the size of the array is reduced, the FSS maintains its frequency response with a very slight change in the center frequency of the stop band. The effect of element size, spacing between the elements, and interleaving the columns of the FSS on the frequency response of the FSS are studied. The effect of the spatial filter on the antenna input impedance is studied over a wide frequency band. The radiation pattern of the bowtie is calculated in the presence 168 Farahat, Hussein, and El-Minyawi of the spatial filter. It is shown that the existence of the later causes considerable reduction in the radiation pattern within the stop band of the filter.