Dual C- and S-Band CMOS VCO Using the Shunt Varactor Switch

This paper proposes a high-performance CMOS voltage-controlled oscillator (VCO) with two subfrequency bands. The VCO consists of two cross-coupled VCOs coupled by a pair of mode-switched inductors. Two pairs of shunt varactors are used to switch highand low-frequency bands. With the varactors as the mode switches, the odd mode VCO operates at the high frequency (C-band) and the even mode VCO operates at the low frequency (S-band). The proposed VCO has been implemented with the TSMC 0.18-μm 1P6M CMOS technology and it can generate differential signals in the frequency range of 5.21-6.66 GHz (IEEE 802.11a) and 3.26-3.84 GHz (IEEE 802.16a) and it also has high output voltage swings at both lowand high-frequency bands. The die area of the dual-band VCO is 0.976 mm × 1.092 mm. At the supply voltage of 0.75 V, the high(low)-band figure of merit is -190.5(-190.4) dBc/Hz.