A Double-looped Complementary -Gm VCO

A 5.2~6.7 GHz voltage-controlled oscillator (VCO) with low power consumption is presented. This VCO is based on a complementary-Gm topology, because of its merit: low power consumption and low phase noise. Nevertheless, the limited tuning-range is inadequate for recent wireless communication system. With a second NMOS cross-coupled pair placed between the gate of the active loads to enhance the positive feedback, the tuning-range can be largely increased, without degrading the phase noise. The prototype is implemented using TSMC 0.18 mum 1P6M CMOS process technology. With 1.6 V supply voltage, phase noise of the VCO is -115 dBc/Hz at 1 MHz offset frequency from the carrier frequency of 5.2 GHz. The figure of merit is -181.8 and total power consumption is 6.43 mW.