Low phase noise power-efficient MMIC GaN-HEMT oscillator at 15 GHz based on a quasi-lumped on-chip resonator

This paper reports on a negative resistance 15 GHz GaN HEMT oscillator using a quasi-lumped integrated resonator. The resonator is based on a lumped element parallel LC resonator and a piece of transmission line acting as impedance transformer and phase compensation. The main advantage of this type of resonator is that it gives good flexibility in choice of impedance level so that it is easy to control the coupling factor between the active device and the resonator which is mandatory to reach good phase noise. An excellent phase noise of -106 dBc/Hz@100 kHz from a 15 GHz carrier is experimentally demonstrated. The oscillator is also very power efficient with a power normalized figure of merit (FOM) of 191 dB, extracted at 100 kHz offset. To the authors´ best knowledge this is the highest FOM reported for a GaN HEMT MMIC oscillator.