An optically tunable cavity-backed slot antenna

There is a growing pressure on antenna designers to provide ever increasing operating bandwidth, efficiency and flexibility. Emerging communications standards are requiring operation over wide frequency ranges, often with multiple, separated bands of operation. This paper proposes and demonstrates an optically tunable cavity backed slot antenna. Through the incorporation of four silicon bridging pieces and a fiber coupled laser, the operating frequency can be tuned between 4.2 GHz and 6 GHz. Antenna efficiency has been measured and ranges between 36% and 62% depending upon the combination of frequency and tuning state, with the gain taking values between 4.3 dBi and 6.9 dBi. An effective fabrication process for the incorporation of silicon into the antenna has been described, as well as methods for effectively simulating the optically generated conductivity. Simulations and measurements show good agreement, and several proposed improvements are proposed for this novel and flexible tuning technology.