Bulk Semiconductor Limiters.

Abstract : The feasibility and significant advantages of the bulk semiconductor approach for the provision of microwave limiter components have been demonstrated by previous research programs. This past work has shown that impact ionization can be utilized in suitable semiconductor structures to provide larger bandwidth and power handling capability than obtainable with conventional semiconductor diodes at both X and Ku-band frequencies. The theoretical model that was developed for the microwave limiting phenomeon also predicts useful limiting at frequencies above Ku-band. The microwave mounting structure that was analyzed and found well suited for the semiconductor limiting element was the resonant slit iris with the element situated in the center of the iris. This structure provided the features of enhanced electric field to produce limiting at lower RF power levels, resonable bandwidth, ease of tuning, and good heat removal. The present program extends and applies this knowledge toward upgrading component performance. During the first quarter, effort was directed toward improving the fabrication and mounting techniques. In addition, test results are given of components using identical elements in single element X-band irises and both single and double element Ku-band irises. A thermal analysis of the limiter structure is presented which aids in predicting the power capability of new designs. For example, the instantaneous peak temperature of the end of a 10 kW, 1 microsec pulse is found to be 260C for a relatively small 3 mil thick element with a 5 mil diameter contact. (Author)