D-Band VCO with Uniformly Low Phase Noise versus Frequency and Temperature

This paper presents a D-band VCO with special focus on low phase noise and high-temperature stability which is enabled by adjusting the oscillation frequency over tuning voltage to its respective impedance minimum according to the negative resistance analysis. Its structure is based on a differential pushpush Colpitts oscillator with second harmonic transformer output. The consumed current amounts to 40 mA with a 3.3 V source and additional 32 mA for the integrated frequency divider. A uniform differential output power of about -1.5 dBm without buffer and low phase noise of -98.7 dBc/Hz at 1 MHz offset is achieved with only little variation over tuning voltage. Phase noise measurements were conducted with particular attention to load pulling effects. In on-wafer measurements, the VCO remains fully functional for temperatures of more than 200 degrees C which demonstrates the efficacy of the proposed design approach.