The large signal design and performance is described for a fully monolithic 22 GHz-band oscillator implemented using a selfaligned AlGaAs/GaAs heterojunction bipolar transistor. The developed oscillator has exhibited an output power of 6.2 dBm at 22.16 GHz with a collector efficiency of 9.5%, and phase noise of -78 dBc/Hz at 100 kHz off-carrier under free-running conditions. These results were in good agreement with the design results obtained using a harmonic balance simulator.<<ETX>>