A Low Voltage Quadrature VCO Implemented With Series Frequency Doublers

Using the transformer coupling technique, this letter presents a new quadrature voltage-controlled oscillator (QVCO) with bottom series-coupled transistors. The proposed CMOS QVCO has been implemented with the TSMC 0.13 mum 1P8M CMOS process, and the die area is 1.03 times 0.914 mm². At the supply voltage of 1.0 V, the total power consumption is 3.56 mW. The free-running frequency of the QVCO is tunable from 5.43 GHz to 5.92 GHz as the tuning voltage is varied from 0.0 V to 1.0 V. The measured phase noise at 1 MHz frequency offset is -117.98 dBc/Hz at the oscillation frequency of 5.5 GHz and the figure of merit (FOM) of the proposed QVCO is -187.27 dBc/Hz.