Performance enhancement of an ultra‐wideband antenna using a compact topology optimized single frequency selective surface‐layer as a reflector

Abstract

In this article, an ultra-wideband (UWB) topology optimized frequency selective surface (FSS) is introduced as a reflecting layer, to maximize the gain and overall performances of an UWB monopole antenna. The single Rogers RO4350B-based FSS layer is synthesized using an automated system, based on an interface bridged between CST Microwave studio and Matlab, and optimized using a binary genetic algorithm. First, the FSS unit cell foot print needs to be as small as possible, while covering a wider frequency range, and to achieve these performances, the proposed genetic algorithm synthesizing system achieved an FSS unit cell with only 0.1 λ × 0.1 λ at the lower-end frequency, covering a bandwidth of 2.9–14.5 GHz. Polarization independence is achieved also, due to the four-folded symmetry imposed on the FSS unit cell. The proposed antenna is designed on a Rogers RO4350B substrate, and backed at a distance of 18.74 mm by an FSS structure. The fabricated prototype shows a bandwidth of 3.1–13.9 GHz, and an excellent maximum peak gain of 9.7 dBi, with an improvement of 3.41 dBi cross the UWB spectrum (from 3.7 to 7.11 dBi), and in good agreement with the simulation results, which made the proposed design a promising candidate for UWB applications requiring high gain, such as ground-penetrating radar, and microwave radiology imaging (MRI) systems.