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A reconfigurable antenna whose size, shape, and polarization can be dynamically modified is a desirable component for today's communication and surveillance systems. To date most proposed reconfigurable antenna concepts have used a matrix of conducting elements connected by electronic/optoelectronic switches with the on-off pattern of the switches defining the size or shape of the antenna. An alternative approach for realizing this concept is to exploit the photoconductive effect in various semiconductor materials. This paper reviews the general theory of photoconductivity in semiconductors emphasizing the parameters relevant to this application. The experimental arrangement and the initial results for our proof- of-concept demonstration are then presented. In this experiment a bow-tie shaped transient carrier distribution was created in a 4 inch diameter, high resistivity (6 - 8 k(Omega) -cm) Si wafer through illumination with a pulsed Nd:Glass laser. The voltage amplitudes measured by the transient Si bow-ties (three different wafers) were 45 - 50% of those received in the same environment by an equivalent copper bow-tie antenna designed to operate from 1.4 - 2.1 GHz. Analysis of this initial data indicates that an optimized design incorporating improved semiconductor processing techniques, an optimized feed/balun, soldered interconnects, and impedance matching would significantly improve performance.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
