A Miniaturized Cavity backed Archemedian Spiral Antenna for mm-Wave Applications

Design of a UWB circularly polarized, cavity-backed Archimedean spiral antenna is presented in this paper. The antenna is designed for 18- 40 GHz frequency range with a binomially tapered parallel-strip to microstrip balun and RF foam absorbent for controlling the backscattering. The peak-measured gain is 4.5 dBi and is greater than 2 dBi for the entire band. The antenna is characterized by greater than 50 degrees 3 dB gain and axial ratio beam-widths which makes it highly suitable for airborne applications. Axial ratio is below 2 dB for the band of interest. The height of the antenna cavity is 19 mm and the diameter is 23 mm giving the antenna a low profile meeting the space requirements of any RF system.