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This letter presents a new low power quadrature voltage-controlled oscillator (QVCO), which consists of two complementary cross-coupled voltage-controlled oscillators (VCOs) with split-source tail inductors. The bottom-series coupling transistors are in parallel with the tail inductors and require no DC voltage headroom. The proposed CMOS QVCO has been implemented with the TSMC 0.18 mum CMOS technology and the die area is 0.512 times 1.065 mm2. At the supply voltage of 1.1 V, the total power consumption is 2.545 mW. The free-running frequency of the QVCO is tunable from 4.38 to 4.71 GHz as the tuning voltage is varied from 0.0 V to 0.6 V. The measured phase noise at 1 MHz frequency offset is -120.8 dBc/Hz at the oscillation frequency of 4.4 GHz and the figure of merit (FOM) of the proposed QVCO is -189.61 dBc/Hz.