A Self-Oscillating Dual Gate MESFET X-Band Mixer with 12 DB Conversion Gain

An x-band receiver stage including preamplifier, mixer and local oscillator has been realized by a dual gate GaAs MESFET in common source configuration. The conversion gain for a signal frequency of 10 GHz and an I.F. of 1GHz was 12 dB by appropriate matching the input (gate 1) and output (drain) port. A variable short, connected to gate 2 controlled the L.O. x-band oscillation. The isolation between drain and gate 1 was 16 dB. Using disc and BaTi4O9 resonator matching on Al2O3 substrate with only I.F. external tuning enabled conversion gain of 5dB. The tuner matched circuit had DSB noise figure of 5.5dB and associated conversion gain of 4dB at an I.F. of 1GHz whereas the best noise figure achieved by the disc-tuned circuit was 7.7dB at an I.F. of 300MHz and associated conversion gain of ¿1.5dB.