DESIGN AND ANALYSIS OF TRI-NOTCHED CIRCULAR PATCH FREQUENCY-SELECTIVE SURFACEâBASED ULTRA-WIDEBAND ANTENNA FOR RADAR AND SATELLITE SYSTEMS

A frequency-selective surface (FSS) integrated into a modified ultra-wideband (UWB) structure is designed and analyzed in this article. The UWB structure consists of a circular patch with three identical cuts optimized on a FR4 substrate (30 × 30 × 1.6 mm<sup>3</sup>), and it is excited by a microstrip line with an impedance of 50 ohms. The bottom rectangular structure of the UWB has one rectangular cut in the center of the surface plane and two triangular incisions at the edge of one side of the back rectangular structure to improve radiation characteristics. With a 6 × 6 FSS structure made of repeated unit cells imprinted on the top surface of another FR4 substrate (60 × 60 × 1.6 mm<sup>3</sup>) placed below the UWB structure, the research aims to minimize minor lobes. Placing polystyrene (60 × 60 × 10 mm<sup>3</sup>), which has a relative permittivity of 2.6, between the FSS structure and UWB structure filters the radiation pattern and directivity at certain electromagnetic-wave frequencies. In the 1.76-12.97 GHz range, the FSS shows a gradually decreasing reflection phase and a notably low transmission coefficient. With its unidirectional emission patterns, the antenna with FSS is a viable choice for ground-penetrating radar applications. It is also a good fit for UWB applications such as radar systems and satellite communication.