A Novel Dual Passive Mixer-first Receiver Front-End with Enhanced RF Carrier Leakage Suppression for UHF RFID Reader

The paper presents a novel on-chip UHF RFID reader receiver front-end with enhanced RF carrier leakage suppression, exploring a dual passive mixer-first with transformer-based matching network architecture. The receiver front-end is composed of 2 paths. In the main path, a bandpass RF input impedance forms by the 4-phase passive mixer and the baseband transimpedance amplifier. Similarly, the auxiliary path is adopted to achieve band-stop input impedance at the input. With the main and the auxiliary mixer designed independently, the high power carrier current flows into the ground through the auxiliary path, while the in-band signal enters the main path to be amplified, thus avoiding the receiver being blocked by the carrier. Furthermore, a transformer is used to enhance the voltage carrier leakage suppression by reducing impedance at both in-band and carrier frequency. Implemented in a 55nm CMOS process, the RF carrier leakage rejection ratio is 22.7dB, which is 9.4dB higher than the single mixer-first receiver. Suffering from +5dBm leakage, the noise figure(NF) of the receiver is 20.4dB. The results demonstrate that the novel receiver front-end architecture is more promising than the single mixer-first structure in RF leakage suppression while keeping high sensitivity.