Broad-Band Tunable GaAs-FET Oscillator with Hybrid-Coupled Microstrip and Evanescent-Mode Resonators

An integrated GaAs-FET oscillator has been developed which provides inexpensive tuning of the oscillation frequency over a frequency range of 950 MHz with little power variation and good efficiency around 8 GHz. This was achieved by coupling the microstrip-mounted FET to an evanescent-mode cavity, which is part of the microstrip box. In a modified version, a varactor diode has been mounted into such an oscillator, permitting additional electronic tuning over 1 GHz around 6 GHz.