Tunable Low Noise GaAs FET Oscillators at 13 GHZ

Today GaAs-FETs are able to generate relative high output power at high frequencies and good efficiency. Therefore they displace GUNN- and IMPATT-diodes in many oscillator and amplifier applications. A big disadvantage of oscillating FETs is their high near carrier noise. But in many cases this problem can be solved by using high Q cavities. In this paper the application of FETs in electronic and mechanical tunable low noise oscillators is shown. A comparison between a feedback and a reverse channel oscillator is made. Measurements of realized circuits are presented. Such oscillators have been developed for use in a digital 13 GHz microwave link system with direct FM service channel.