A Ka-Band High Power and Low Phase Noise GaN MMIC Oscillator with a Compact Open-Loop Folded Resonator Filter

This paper presents a Ka-band high power and low phase noise GaN oscillator with a 2nd-order folded open loop filter employed in the feedback loop. The concept of complex quality factor (Qsc) is employed to precisely determine the oscillation frequency. The parasitics of the GaN transistor are extracted, revealing a Qsc peak of 236 at 30.6 GHz for the overall passive network. Experimental results demonstrate an oscillation frequency of 30.5 GHz, closely matching the simulated results. Phase noise (PN) measurements yield -113.3 dBc/Hz and -136.8 dBc/Hz at 1 MHz and 10 MHz-offset frequency, respectively. The peak output power is 10.4 dBm with a figure-of-merit (FoM) up to -184.7 dBc/Hz, demonstrating performance among the best compared to published GaN MMIC oscillators in a similar frequency range. The core chip area is only 1.62×0.73 mm².