A UHF RFID reader receiver is implemented in 0.18μm CMOS. The direct-conversion receiver consists of an LNA, passive mixers, baseband PGAs and LPFs. As high as 18.5dBm measured IIP3 of RF front-end is achieved by using passive mixers driven by 25% duty cycle square wave LO. To optimize noise performance, the bandwidth of LPFs is programmable according to different data rate. The an-noying DC offset is cancelled by off-chip passive DCOC loops. The receiver has a sensitivity of -77dBm in normal mode and -87dBm in LBT mode. The total power dissipation in normal mode is 74mW from 1.8V power supply.