A High Isolation Rate Race Circuit Compose the Carrier Leakage Canceler for RFID

In order to suppress Tx-to-Rx carrier leakage in Radio Frequency Identification (RFID) system, this paper proposes the method of carrier leakage canceler of rate race circuit. It uses the two outputs of rate race circuit as antenna port and reflection port, and the imperfect isolation (Tx-to-Rx) and the reflection of antenna mismatch are suppressed in the receiver by adjusting the reflection coefficient of reflection port. Simulation shows that using rate race carrier’s cancellation circuit can perfectly suppress the carrier leakage in receiving circuit, the carrier’s suppression ration reaches 71.7dB which is 36dB higher than traditional circulator. Finally, the practice circuit is tested, and the result of test shows that carrier suppresses 61dB, which has a good application value in engineering