Low-Cost Vertical Patch Antenna With Wide Axial-Ratio Beamwidth for Handheld Satellite Communications Terminals

This paper presents a low-cost circularly polarized (CP) small antenna for handheld satellite communications terminals in S-band. It consists of an elliptical vertical patch antenna (VPA) element backed by an elliptical air cavity of different ellipticity. Two dielectric substrates, each with an elliptical opening, are stacked together and mounted onto a ground plane. The rim on the smaller opening of the upper substrate is conveniently plated with conductor to form the VPA, whereas the larger opening of the lower substrate and the ground plane forms the air cavity. The elliptical VPA, when excited by a probe feed, generates CP radiation. Dielectric loading of the VPA not only achieves its size reduction but also widens the 3-dB beamwidth. The fabricated antenna has a measured gain of 5.1 dBic at 3.71 GHz, impedance bandwidth of 12.6%, 3-dB beamwidth of 102° and axial-ratio beamwidth (AR <; 3.0 dB) of 121°.