An X-Band Superharmonic Injection-Coupled Quadrature VCO (IC-QVCO) with a Tunable Tail Filter for I/Q Phase Calibration

A superharmonic injection-coupled quadrature oscillator topology (IC-QVCO) for low power low phase noise quadrature signal synthesis is introduced. A tunable tail filter (TTF) reduces the oscillator phase noise and calibrates the residual quadrature error in the presence of a 3-sigma variation in the device parameters. As a proof of concept, a 9 GHz prototype is implemented in a 0.18 mum RF CMOS process, and achieves a measured phase noise figure of merit (FoM) ranging from 177.3 to 182.6 dBc/Hz along the 9.0 to 9.6 GHz frequency tuning range while draining only 5 mA from a 1.8 V power supply. Phase error tuning up to plusmn11deg is demonstrated using time domain measurements. In comparison, an identical IC-QVCO without the TTF was measured to have 1-4 dB worse phase noise performance across the tuning bandwidth.