This article describes the development of a high-gain, broadband, circularly polarized Fabry–Perot cavity (FPC) antenna for high-data-rate communication in CubeSat/SmallSat applications. In this work, the concept of spatially separated superstrate area excitation is developed for the first time in FPC antennas. This concept is then validated and applied to increase the gain and the axial ratio bandwidth of a conventional narrowband circularly polarized source patch antenna. The antenna’s design leverages independent control of polarization at different frequencies, resulting in a large overall bandwidth. The fabricated prototype antenna provides right hand circular polarization with a peak measured gain of 15.73 dBic over a common bandwidth of 1.03 GHz ranging from 7.99 GHz to 9.02 GHz. The gain variation over the bandwidth is less than 1.3 dBic. The antenna measures 80 mm × 80 mm × 21.14 mm and is simple, lightweight, easily integrable with CubeSat body, and useful for X-Band data downlink. When integrated with the metallic body of a 1U CubeSat, the simulated gain of the antenna increases to 17.23 dBic, with a peak measured gain of 16.83 dBic. A deployment method is proposed for this antenna that results in a total stowed volume of only 2.13λo× 2.13λo× 0.084λo(0.38\documentclass[12pt]{minimal}
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