Broadband Transmitarray Antenna Design Using Polarization-Insensitive Frequency Selective Surfaces

Abstract

Applications of frequency selective surfaces (FSSs) for transmitarray antennas (TAs) are investigated. Two broadband polarization-insensitive FSS elements are proposed and their transmission performances are evaluated against the desired amplitude and phase responses for this application. Accordingly, two small aperture $\left({{20}\,\text{cm} \times {20}\,\text{cm}} \right)$ broadband TAs are designed and their radiation characteristics are compared to each other. The simulated results show a maximum aperture efficiency of (38.4% and 36.7%), $- {1}\,$ and $- {2}$ dB gain bandwidths of (13.5% and 11.8%) and (16.08% and 19.75%) for the first and second TA, respectively. The antenna with superior performances is successfully fabricated and tested as a proof of concept. The measured maximum aperture efficiency of this TA is 34.64% and its $- {1}$ and $- {2}$ dB gain bandwidths are 10.2% and 14.83%, respectively. Moreover, the scanning performance of this antenna is also investigated by changing the feed location and it is shown that reasonable results in terms of sidelobe levels $(\text{less than } {-}{15}\,\text{dB})$ , appearance of shoulder and coma lobes, and gain loss $(\text{better than } {-}{3}\,\text{dB})$ are achieved for scanning range up to $\pm {35}^\circ $ in both E- and H-planes. In addition, a new low-cost cavity-backed folded dipole antenna (CBFDA) is also proposed as a feed for TAs in this work. The introduced feed offers the required radiation pattern to illuminate the designed FSSs.