A wideband CMOS VCO for zero-IF GSM-CDMA single-chip transceiver

This paper presents a low-power CMOS VCO in a 0.35 /spl mu/m process which achieves a tuning range of 2.47 GHz-3.47 GHz and phase noise performance of -145dBc/Hz at 3 MHz offset (from a 1.8 GHz carrier). 5-bit digital coarse-tuning and accumulation-type MOS varactors allow for a 33% tuning range, which is required to cover the LO frequency range of a zero-IF GSM-CDMA transceiver and to account for process and temperature variations. Optimum design techniques ensure low VCO gain (<104 MHz/V) for good interoperability with the frequency synthesizer. An integrated regulator provides low supply pushing (40 kHz/V) and reduces the AM-to-PM sensitivity from the supply.