A 1-18 GHz photonically-reconfigurable phased-array antenna

A photonically-controlled, reconfigurable phased-array antenna concept, based on the principle of laser activation of photoconductive silicon, is described. Its novel features include reconfigurability, steerability, low radar cross-section, wide-frequency capability, multifunctional use with a shared aperture, and modularity. The distinguishing feature of the concept is the use of photoconductive silicon bowtie radiating elements, which are activated by laser light. Conceptual array architecture consists of a vertical card design which offers improved structural capability and is modular, enabling easy replacement or rework of cards. Preliminary design of a 30.5 cm×30.5 cm vertical-card array, which includes photonic cards, ground plane, and radome for a 1-18 GHz phased-array antenna, is presented. Preliminary results indicate the required optical power (0.6-0.8 W/cm²) for acceptable RF performance and illumination efficiency is satisfactory. Further improvements in photonic efficiency (target of 0.1 W/cm²) are anticipated using highly-efficient multilayered dielectric coatings, optimized metallization patterns on the silicon radiating elements, and improvements in the optical-fiber feed system. RF modeling suggests a minor influence of “off”-state elements on the radiating patterns of an active silicon center element. Metallization of the radiating elements results in a 2× reduction in silicon active area, and corresponding reduction in optical power demand