A waveguide-cavity multiple-device FET oscillator

A waveguide-cavity oscillator, applicable to power-combining circuits, has been developed using probe for coupling between active device and cavity. No lossy stabilizing element is required. The control of output power, oscillation frequency, and injection locking bandwidth are performed easily. Output power of 44 mW and dc-RF conversion efficiency of 33.2 percent were obtained at 9.2 GHz for a single-device low-power FET oscillator. A simple technique of cascading the pretuned oscillator modules was used to construct multiple-device oscillators incorporating up to four FETs with combining efficiency of about 100 percent.