QUASI-OPTICAL VCOS

Quasi-optical grid voltage controlled oscillators are presented. These VCOs are the first demonstration of a quasioptical system consisting of several periodic arrays loaded with solid-state devices. A quasi-op tical VCO consists of an array of oscillators, a variable capacitance array, and a mirror. The mirror provides feedback for locked power com bining of a large number of MESFET oscillators that load a two-dimensi onal metal grid on a dielectric substrate. The frequency can be electr ically tuned either with gate bias or with another array loaded with v aractor diodes. When the varactor bias voltage is changed, the capacit ance of the diodes changes, which in turn modulates the frequency of t he output power-combined wave. Two types of arrays are presented, one consisting of short dipoles, and the other of bow-tie elements. As exp ected, the bow-tie VCO has better performance than the dipole VCO, due to its broadband impedance. A 10% tuning bandwidth with less than 2 d B power change was measured in the case of a bow-tie VCO.