ISSN (Online) : 2319 - 8753 ISSN (Print) : 2347 - 6710 International Journal of Innovative Research in Science, Engineering and Technology An ISO 3297: 2007 Certified Organization Volume 4, Special Issue 9, July 2015 National Conference on Emerging Technology and Applied Sciences-2015 (NCETAS 2015) On 21 st & 22 nd February, Organized by Modern Institute of Engineering and Technology, Bandel, Hooghly-712123, West Bengal, India Copyright to IJIRSET www.ijirset.com 15 Design of a Compact Patch-Type Frequency Selective Surface with Multiple Bands and Enhanced Bandwidth Diptargha Baul, Kunal Nandi, Manojit Roy, Partha Pratim Sarkar Department of Engineering & Technological Studies, University of Kalyani, Kalyani, West Bengal, India ABSTRACT: This paper deals with the design of a patch type frequency selective surface (FSS). The structure comprises of metallic patches being sandwiched between two dielectric layers of the same material (ε r =2.4) and equal thickness (1.6mm). The initial -10dB percentage bandwidth was 2.97%, which eventually is enhanced to 33.60%. The first resonant frequency is decreased by 31.6%, so the design offers more than 50% compactness and in addition, offers multiple bands too. KEYWORDS: metallic array, array of apertures, resonant frequency, periodic boundary, transmission characteristics, parametric study. I. INTRODUCTION A typical frequency selective surface is a two-dimensional metallic array printed on a dielectric slab or array of apertures within a metallic screen, separated by some finite periodicity from each other [1]. When the FSS is illuminated with plane wave, it acts as a microwave filter by allowing some frequencies to transmit through and some to reflect back. Two types of generic geometries of FSS are there. The first one, commonly known as patch-type, acts as a band-reject filter, exhibits total reflection at the resonating frequency, and another type is aperture-type, which exhibits total transmission at resonating frequency, thus performs as a band-pass filter [2]. For an FSS unit cell, there is a relationship between the dimension of the patch and the frequency at which that structure would resonate, involving wavelength. For any periodic surface to have a stable resonant frequency with angle of incidence, the inter-element spacing should be around 0.4 [3]. In recent years, FSSs are used as filters in the wireless communication system [4]. FSSs are used in airborne radomes, absorbers, and electromagnetic band gap material etc [5]. In this paper, initially an FSS design is proposed which has an extremely large periodic boundary, to attain the practical resonant frequency identical to the calculated one, thus giving an extremely low bandwidth, and ultimately an optimised design is achieved by certain modifications to present a compact-wideband frequency selective surface with multiband operation facility[6-8]. The structures are all simulated in Ansoft designer version 2. II. FSS UNIT CELL DESIGN The basic FSS unit cell consists of a metallic patch (material copper, dimension 50mm x 25mm and negligible height) sandwiched between two dielectric substrates (material GlassPTFE, height 1.6mm, relative permittivity(ε r ) 2.4, and dimension 100mm x 125mm), as shown in Figure 1. The grey portion represents the dielectric layer and the dark portion represents the metallic patch.