Active element microwave power coupler

Abstract

Microwave couplers such as power splitters and combiners for coupling a common terminal to two branch terminals are disclosed which are compact and provide gain. Each leg of the branching circuit comprises a dual gate FET device. The dual gate FET device has its first gate connected to receive an input signal, its second gate biased and terminated in accordance with the phase shift desired from that FET device and its drain coupled to provide an output signal. Where equal phases are desired from both legs, the second gates of all of the FET devices are capacitively terminated. Where a differential phase shift is desired over the two legs, the second gate of the FET device in one leg is capacitively terminated and the second gate of the FET device in the other leg is inductively terminated. The bias voltages on the second gates are preferably selected to produce the same gain for both. Coupling the first gates of both legs to the common terminal and the drains to separate branch terminals yields a power splitter. Coupling the two drains to the common terminal and the first gates to separate branch terminals yields a power combiner.