A low-noise VCO with a constant KVCO for GSM/GPRS/EDGE applications

A low-noise LC-tank VCO with a constant K_VCO for GSM/GPRS/EDGE applications is presented. The proposed compensation technique helps to minimize the K_VCO variation within the operation frequency of interest. This VCO is incorporated with a fractional-N frequency synthesizer and a DCT and is implemented in a 0.13 mum CMOS process. The measured K_VCO is 29 MHz/V with a plusmn10% tuning range for a single sub-band and the overall K_VCO variation is plusmn2.5% when the compensation technique is enabled. Based on this low-noise VCO, the achieved DCT phase noise is -165 dBc/Hz at a 20 MHz frequency offset from a 915 MHz carrier and a SAW-less DCT in the 2 G mobile application becomes feasible.