Periodic microstrip leaky-wave antenna with optical beam scanning capabilities

This work investigates the feasibility of achieving dynamic beam scanning using optical control as applied to a periodic leaky-wave microstrip antenna. Optical control is implemented by illuminating periodic silicon elements placed along the length of the microstrip antenna. By varying the intensity of the optical illumination, induced conductivity changes in the silicon elements alter the antenna propagation constant and cause the peak of the radiation pattern to scan in space.; Leaky-wave behavior is first characterized by using a passive antenna design approach to investigate the effects of element size and periodic separation on radiation performance. Optical control is then integrated into the passive design using periodically placed silicon elements along the length of the microstrip structure. These elements are illuminated from below through a series of holes etched into the ground plane in order to avoid field obstruction in the front region of the antenna. These holes were found to introduce significant backside radiation, degrading antenna gain. Simulation results, for this structure, indicate that optical illumination with excess carrier concentration densities ranging up to 1017 cm-3 will produce beam scanning in the order of 5 degrees. Measured results were inconclusive. Several improvements are recommended for future work including, avoiding stop band regions, implementing an optically transparent ground plane and increasing the optical illumination intensity. Implementing these recommendations will lead to improved performance establishing the feasibility of the above antenna design.