CMOS Quadrature VCOs Using the Varactor Coupling Technique

This letter presents a new quadrature voltage-controlled oscillator (QVCO), which consists of two complementary cross-coupled voltage-controlled oscillators (VCOs) coupled via varactors. The proposed CMOS QVCO has been implemented with the TSMC 0.18 μm CMOS technology and the die area is 0.61 × 0.95 mm
²
. At the supply voltage of 1.2 V, the total power consumption is 3.7 mW. The free-running frequency of the QVCO is tunable from 3.86 GHz to 4.22 GHz as the tuning voltage is varied from 0.0 to 1.2 V. The measured phase noise at 1 MHz frequency offset is -123.42 dBc/Hz at the oscillation frequency of 3.94 GHz and the figure of merit (FOM) of the proposed QVCO is -190.38 dBc/Hz.