Injection-locked push-pull oscillator at 72 GHz band using cross-coupled HEMTs

An injection-locked push-pull oscillator at V-band is developed for high purity millimeter wave signal source. Cross-coupled HEMTs are applied for the negative resistance generation across wide frequency range and virtually grounded short-ended lines are used for the resonant circuit instead of lumped inductors. Thanks to the differential operation of cross-coupled HEMTs, the push-pull oscillator was easily implemented by combining the 2nd harmonics of oscillation signal at the drain terminals. Injection signal at the fundamental oscillation frequency is applied at the gate of the current source FET of cross-coupled FETs for stabilizing the oscillation, which performs the amplification and harmonic generation. The designed oscillator was fabricated using 0.15μm GaAs pHEMT process. The measurement showed the free-running oscillation around 35.8 GHz and maximum lock range of 1.48 GHz (2.1%) around 71.6 GHz with the average output power of -6 dBm.