Implementation of Carrier-Cancellation Circuit for UHF RFID Reader RF Front-End using Genetic Algorithm Optimization

A problem of ultra-high frequency radiofrequency identification (UHF RFID) reader is the reading range because one antenna is used for transmitting carrier and backscattered signal. In this study, a carrier-cancellation circuit is used with a commercial directional coupler to obtain a good isolation between transmitter (Tx) and receiver (Rx) by suppressing the transmitting leakage signal. The suppression level of the circuit can be obtained by applying the Genetic Algorithm (GA) to optimize values of digitally tunable capacitors. Experimental result of the S24 of the directional coupler is approximately of -70 dB which showed the good isolation between Tx and Rx at 900 MHz.