A compact and high gain resonant cavity antenna (RCA) is investigated in this work. At first, a ray-tracing model and the full-wave analysis are presented to clarify the characteristics of RCA in cases of finite lateral size and inhomogeneous superstrate. In consequence, a novel compact, high gain, and wideband RCA is proposed. The RCA consists of a via hole feed patch and an array of hybrid parasitic rings fabricated on a superstrate. The via holes feed patch with a high radiation directivity significantly enhances the RCA's gain. On another hand, the dimension and bandwidth of the RCA are improved by the hybrid parasitic ring superstrate which is constituted by non-periodic parasitic patch and rings. Finally, a prototype of the RCA is fabricated and measured. With only the dimension of 1.35λ 0 × 1.35λ 0 × 0.63λ 0 , the peak gain of 15.8 dBi and 3 dB gain bandwidth of 10.7% are obtained. INDEX TERMS Resonant cavity antenna, compact, high gain, non-periodic microstrip superstrate, hybrid parasitic ring.

The scenario of using a spatially distributed antenna for miniaturized applications is presented in this work. A model of lens antenna with a low profile, compact, and high focusing superstrate, which exquisitely combines the conventional lens and resonant cavity superstrates, is proposed. Based on this model, the parasitic lens superstrate is introduced with high performance and simple configuration. The parasitic lens includes a low dielectric substrate and high resonant parasitic elements. By manipulating the surface currents of parasitic elements concentrating at center region of superstrate, the focusing effect is obtained. A prototype of the parasitic lens antenna was implemented with the source and parasitic superstrate's lateral dimensions of 0.5λ 0 × 0.5λ 0 and λ 0 × λ 0 , respectively, and the profile of 0.54λ 0. The peak gain is 10 dBi, corresponding to the enhancement of 5 dB. The measured results perspicuously demonstrate the efficiency of the compact parasitic lens. INDEX TERMS Antenna miniaturization, compact, gain enhancement, high focusing, parasitic lens.