A Frequency Selective Feedback Receiver For Multi-Bands Operation

For a frequency-division duplex (FDD) wide-band code-division multiple-access (WCDMA) system, transmit (TX) signal leakage at the receiver input degrades the receiver performance. To cancel this TX leakage, a frequency selective feedback was previously proposed, but it had an unpredictable feedback loop characteristic due to the uncertainty of the duplexer impedance. This paper presents a new method to achieve TX leakage cancellation regardless of the duplexer impedance. In addition, a local oscillator (LO) phase shift technique is proposed to apply this method for multi-band. A receiver adopting these proposed techniques is implemented using a 0.18-m CMOS process to prove the concept. The measured TX attenuations of the high- and low-band are 17-dB and 20-dB, respectively, and the measured noise Figure (NF) degradations of the high- and low-band are 0.6-dB and 0.5-dB, respectively. The measurement results demonstrate effectiveness of the proposed techniques.