Study of optically controlled microwave components

Optically controlled microwave devices in microstrip geometry have been investigated in this thesis. First, the photo-conductance model for a microstrip gap, taking into account the carrier diffusion, is developed and the photo-conductivity measurement is carried out at dc and microwave frequencies. It is shown that the measured microwave photo-conductance for the gap is about 20 times higher compared to its dc value. The result has been explained with the help of a Schottky diode formation at the metal-semiconductor contact. Two types of optically controlled phase shifters namely reflection-type and Mach-Zehnder interferometer-type are proposed, analysed, developed and experimentally studied. The phase characteristics of the phase shifters as a function of the optical intensity and microwave frequency have been investigated. It is shown that a phase shift between 0 and +-180 degrees with an insertion loss of about 2dB can be realized with an optical power of 50 -l00mW. A new class of antenna called Photo-induced Semiconductor Antenna is theoretically studied. More Info

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