Off-broadside antenna beam generation based on photoconductivity technology

The non-mechanical beam deflector forms and scans at a rapid rate a beam of millimeter wave (MMW) radiation coming from a MMW source. The beam deflector includes a semiconductor body in which a spatially varying density of charge carriers is selectively injected, e.g. through selective optical exposure using an LED array. The injected charge carriers - electrons and/or holes - alter the dielectric characteristic of the semiconductor body locally and thereby attenuate and reflect the incident MMW radiation. The injection can be achieved by illuminating the semiconductor wafer by a high power light source. The part of the wafer, which is illuminated, will change the amplitude and phase of the waves coming from the MMW source. Since the optical masking can be rapidly reconfigured, the beam can be scanned through selective control of the injected charge carriers. An appropriate control circuit as part of the LED array can achieve this. Two different techniques namely the Fresnel-Zone Plate (FZP) and the Reflect Phased Array (RPA) are suggested to realize the antenna. This paper gives the concept of the two approaches, the simulation results for RPA, and measurement results for the amplitude of the reflected and transmitted microwaves.