Investigations on the design and development of conformal frequency selective surface variants

Abstract

This thesis explores the design and development of conformal Frequency Selective Surfaces (FSS) for X-band applications. The research focuses on the development of separate bandpass and band-stop FSS screens, all designed on a flexible substrate. The research demonstrates the utilization of the flexible material for the development of distinct FSS components. A bandpass FSS that selectively transmits specific frequency ranges, and a band-stop FSS that effectively attenuates unwanted frequencies. By integrating these functionalities into flexible substrates, the study advances the capability of FSS technology to conform to varied surfaces and dynamic environments. The thesis presents a thorough examination of design principles, simulation results and experimental validations on the performance of flexible FSS components in modern communication and RADAR systems. The first part of the thesis presents a conformal band-stop frequency selective surface for electromagnetic shielding applications. The study presents a novel band-stop FSS designed for X-band applications. The single layer FSS features frequency-dependent conductive patterns on a polyimide substrate, ensuring attenuation across the entire X-band range. The unit cell of the FSS is configured with an octagonal loop, where each side alternates between thick conductive patches and stub lines to achieve a rejection bandwidth from 8 to 12 GHz with |S21| and#8804; -15 dB. With a unit cell size of 0.167and#955;o × 0.1673and#955;o, where and#955;o represents the free space wavelength at the center frequency, the FSS demonstrates mode-independent characteristics due to its rotational symmetry. Analysis of the bending behavior reveals that the FSS maintains its performance when flat or curved. Furthermore, the ultra thin design ensures a stable frequency response for both normal and oblique incidences up to 80 degrees. newline