GaAs Bipolar Broadband Oscillators

The GaAs heterojunction bipolar transistor (HBT) has been investigated for use in oscillators due to its combination of low flicker noise and high frequency performance. The HBT characteristics in oscillators have been assessed by constructing both varactor tuned oscillators (VTO) and, for the first time, YIG tuned oscillators (YTO). Tuning range, output power and phase noise are described for both types. The YIG tuned oscillator exhibits phase noise better than -110dBc/Hz at 100kHz off carrier which is the lowest phase noise reported to date for a tuneable HBT oscillator.