Design of a high-linearity RF front-end with IP2 calibration for SAW-less WCDMA receivers

A fully integrated receiver RF front-end designed in 0.13μm CMOS that meets the WCDMA system requirements is presented. The receiver RF front-end requires no interstage SAW filter. To handle the stringent linearity requirements in terms of both IP3 and IP2 set for the RF front-end, a current-mode passive mixer constructing a built-in high-Q bandpass filter is adopted to suppress blockers including the transmitter leakage, and an IP2 calibration circuit is applied to the mixer. A new start-up circuit is proposed for the operational amplifier in the transimpedance amplifier. To generate the quadrature clocks, a three-stage RC polyphase filter is used. The measurement results show that, owing to this high-linearity RF front-end, the receiver achieves -15dBm IIP3 and +72dBm IIP2, which satisfies the WCDMA SAW-less requirements.