On the Characteristics of the Highly Directive Resonant Cavity Antenna Having Metal Strip Grating Superstrate

Various resonant cavity antennas (RCAs) having different metal strip gratings (MSGs) as their superstrates are studied in terms of their directivity and scanning properties using transverse equivalent network (TEN) model in conjunction with the periodic method of moments (MoM). It is shown that radiation patterns in E- and H-planes coincide over a wide angle range in RCAs when their MSG superstrates are free-standing and highly reflective, as reported in the previous literature. However, using less reflective MSG or employing dielectric support in the MSG superstrate degrades the equality of E- and H-plane radiation patterns. Moreover, as the scan angle increases, radiation patterns in E- and H-planes become noticeably different. It is elucidated that this is due to the angular dependence of the reflection coefficient phase of the MSG superstrates. A comparative study is also performed on a few different RCAs based on both simulation and measurement results. It is illustrated that in practice when the excitation source of the RCA is a probe-fed microstrip antenna and the RCA is finite in size, cross-polarization increases considerably as opposed to the RCAs having ideal sources and, infinite ground plane and MSG superstrate in the transverse direction.