Pin diode switchable capacitance arrays

The contract requirement was the development of a monolithic 10 capacitor/pin diode array to be used as a tuning element in an electronically tuned filter. The initial integrated circuits exhibited stray capacitances between the circuit elements through the high resistivity silicon substrate and the MOM capacitors did not have a high enough Q for optimum circuit performance. Therefore, the remaining effort was directed toward the development of a discrete PIN diode with a low enough RF resistance in conjunction with the required capacitance value to combine with high Q microwave capacitors in a hybrid circuit. This diode/capacitor array fits into a 0.6 x 0.4 inch area which reduced the number of available devices to six from ten due to the size of the units. This is the array which was finally delivered. The hybrid array occupies much more area than the proposed integrated circuit, but it appears to be the best way to reduce the parasitics of the capacitor/diode array.