Design of L-band microwave oscillators

Abstract

Oscillators are basic microwave energy sources for all microwave communication systems. Transistor oscillators can be realised using either bipolar or GaAs FET devices. This paper discusses the theory and fabrication of 1.7 GHz negative resistance and feedback type GaAs FET oscillators. A microstrip resonator has been used in the design of the negative resistance oscillator and a feedback type oscillator utilises a lumped element resonator in a feedback network. Simulation for both oscillators has been performed using Agilent ADS software. Both oscillators have been fabricated on an FR 4 PCB. The negative resistance oscillator operating at 1.66 GHz delivers +7.89 dBm output power to the 50 /spl Omega/ load. The feedback type oscillator operating at 1.47 GHz exhibits an output power of +9 dBm. The performance of those oscillators has also been compared in terms of phase noise, showing superior results for the feedback type oscillator.