A method to improve isolation for RFID applications

The isolation between transmitter and receiver has been a critical problem in a pulse-modulated RFID (radio frequency identification) system where transmitter and receiver use the identical frequency. A method using a switch, a mixer, a BPF (band-pass filter), and an additional oscillator in the transmitter is proposed to improve the isolation between transmitter and receiver in an RFID system. The proposed system up-converts the outgoing wave from a frequency different from the received signal and improves the isolation. The proposed method provided additional 20 dB improvement on the isolation.