X -Band Harmonic-Tuned High Power and Efficiency GaN HEMT Oscillator IC

An X-band harmonic-tuned oscillator integrated circuit (IC) with high power and efficiency is presented, utilizing gallium nitride (GaN) high electron mobility transistor (HEMT). It consists of a feedback and load network to provide optimal harmonic impedances while satisfying the oscillation condition at the fundamental frequency. The feedback network is synthesized from harmonic load-pull simulations and further simplified into a circuit comprising capacitors and transmission line, eliminating the inductors. This modification serves to reduce losses, which in turn improves output power and efficiency, while also reducing circuit area. The feedback network incorporates parallel resonant shunt stubs to enhance frequency selectivity and facilitate harmonic impedance matching, while also serving as a bias circuit. The oscillator, fabricated using a 250-nm GaN HEMT process, achieves a high output power of 35.0 dBm delivered to the load at 10.5 GHz, demonstrating a remarkable efficiency of 48.9% and excellent phase noise at -124.9 dBc/Hz with a 1 MHz offset. These results indicate a significant improvement in power and efficiency compared to previous X-band watt-level GaN oscillator ICs.