A multi-band WCDMA SAW-less receivers with frequency selective feedback loop

For frequency division duplex (FDD) wide band code division multiple access (WCDMA) system, transmit (TX) signal leakage at the receiver input degrades the receiver performance. Previously, to cancel the TX leakage, a frequency selective feedback was proposed, but it had the unpredictable feedback loop characteristic due to the uncertainty of the duplexer impedance. This paper proposes a new method to achieve a predictable feedback loop characteristic. In addition, to achieve the TX leakage cancellation for multi-band, a local oscillator (LO) phase shift technique is also presented. The proposed receiver which was composed of high- and low-band LNAs and mixers, the TX canceller, and the LO shifter was implemented using 0.18-μm CMOS process and is under fabrication. Simulation results met the required specifications which were delivered from the WCDMA specifications.