A Wideband Resonant Cavity Antenna With Compact Partially Reflective Surface

A novel wideband resonant cavity antenna (RCA) with compact partially reflective surface (PRS) is presented, which is composed of a superstrate and a feed antenna. The superstrate is a dielectric slab with double-deck periodic array structure, where the superstratum is composed of square loop cells and substratum is composed of square loop aperture cells. This shows positive reflection coefficient phase, which in turn helps in obtaining wider RCA bandwidth. Contrary to the patch cell periodic array, a periodic array composed of square loop cells provides further compact structure. The feed system is a wideband aperture-coupled patch antenna, which is composed of square patch, ground plane with I-shaped slot, and fork-shaped feed network. This dual-arm feed network helps in obtaining the maximum gain at the center frequency. The superstrate with positive reflection coefficient phase provides the minimum gain at the resonant frequency. This in turn helps RCA in obtaining invariant gain in the operation band. Experimental verification was performed and the results show that this RCA offers fractional bandwidth of around 23.6% at X-band (8.88-11.25 GHz, S11 ≤ -10 dB) and gain (13.36-13.92 dBi) is almost invariant over the bandwidth. The measured patterns are symmetric with low cross-polarization levels.