Temperature compensated VCO design for multi-band WCDMA transceiver application

A Voltage Controlled Oscillator (VCO) with temperature dependent frequency drift compensation technique has been implemented for 3G cellular application in commercial 0.18 um SiGe BiCMOS process. Additional MOS Varactors are used in the tank and biased with PTAT voltage to achieve the frequency drift compensation over temperature. With this new technique, VCO can achieve very stable frequency of 17.4 ppm/°C at 3.8 GHz and 16.5 ppm/°C at 3.3 GHz. Measurement results also show that VCO can cover frequency range of 3050 MHz to 4207 MHz with the phase noise of -116 dBc/Hz at 1 MHz offset and -138 dBc/Hz at 12.5 MHz. The VCO only draws 4 mA of current from 2.8 V supply voltage.