20 GHz integrated CMOS frequency sources with a quadrature VCO using transformers

A fully integrated 20 GHz frequency source is implemented with a VCO and a doubler in a 0.18 μm CMOS process. A 10 GHz quadrature voltage controlled oscillator (QVCO) is implemented using a transformer-coupled resonator. The VCO can be tuned between 10.2 and 11.4 GHz and has low phase noise of -118.67 dBc/Hz at 1 MHz offset frequency with 1.8 V power supply. The figure of merit (FOM) is 188 dB. The 20 GHz differential signal is generated by harmonics of quadrature signals of the VCO with a balanced frequency doubler. To increase the output power of the harmonics, pinch-off clipping is used without any buffers or DC level shifter, since the proposed VCO has RF signals with low DC level. The frequency multiplier, the output of which can be tuned between 19.8 and 22 GHz, has a low noise of - 111.67 dBc/Hz at 1 MHz offset frequency. The phase noise of the multiplier is 7 dB higher than that of the VCO. The output power is -6.83 dBm and the VCO output power is -6 dBm.