An integrated 10/5GHz injection-locked quadrature LC VCO in a 0.18 µm digital CMOS process

We present a 5GHz quadrature LC voltage controlled oscillator based on super-harmonic injection locking to an on-chip free-running 10GHz master oscillator. The oscillators are fabricated in a 0.18µm, low voltage digital CMOS process with a lossy substrate (ρ ∼20mohm-cm) and thin (1.6/µm), high resistivity M6. All the oscillators use fully integrated, low Q (∼4) spiral inductors. The 10GHz master oscillator achieves a tuning range of 1.4GHz, and a phase noise of -118dBc/Hz at a 1MHz offset. We measured the phase noise of the quadrature VCO to be 6dBc/Hz lower than that of the free-running master oscillator. The oscillator core draws 14mA from a 1.6V supply. An image reject receiver built using the quadrature signals provides nearly 40dB of image rejection, confirming better than 1° of quadrature matching. An on-chip frequency locked loop is shown to guarantee capture and accurate quadrature generation in the presence of an additional artificially introduced, 10% mismatch in the natural frequencies.