Abstract
A new design for active filtering technique, used to remove the transmitted leakage signal in frequency division duplex (FDD) RF front-end transceivers, is presented. In this technique, the front-end SAW filter is replaced by an active on chip bandpass filter. The proposed design covers all the UMTS bands as it can be controlled by switches to select the desired band of operation. The filtering technique is based on using a bandpass sink filter to selectively filter the transmitted leakage before the downconversion mixer, while not affecting the desired signal gain. The proposed circuit achieves (57 dB to 62 dB) of signal-to-leakage ratio for different UMTS bands. Designed in 0.13)mu m CMOS process, the proposed technique improve the IIP2 by 7 dB. However, the noise figure (NF) is degraded by 1.5 dB. The sink filter draws 4.8 mA current from 1.6 V supply.