A common-gate down-conversion mixer with capacitive cross-coulping technique for UHF RFID applications

This paper proposes a common gate down conversion mixer with Capacitor Cross Coupling (CCC) technique designed for UHF 900 MHz RFID reader receiver chain. In this work, the common gate (CG) topology in the input stage has been applied to achieve high saturation level to expand voltage swing range. But due to the disadvantage of CG topology, it has poor gain and noise performance. Consequently, the technique of capacitor cross-coupling (CCC) has been adopted to improve conversion gain and noise figure (NF) based on CG topology. The mixer performance with and without the technique of CCC is compared. The operating frequency is 900MHz in UHF band. This circuit has been simulated in cadence Spectre environment and implemented in Tower Jazz 018 CMOS process under 3.3V supply. The simulation results show the improvement on conversion gain and Noise Figure (NF) by 4.5dB and 1.3dB, respectively. And the variations of CCC, from 0.2pF to 4pF, are implemented to get knowledge of performance varying dependent on CC capacitance.