High-voltage analog front-end circuit for a magnetically-coupled RFID transponder

An analog front-end circuit for a 125-kHz RFID transponder has been designed by using a 0.35-mum high- voltage CMOS process. Due to the use of high voltage MOS transistors in all constituent circuits, RF-to-DC power conversion has been achieved at the maximum coupling coefficient without RF limiter circuits, thus saving significant chip area. Furthermore, large load modulation depth is also permitted to achieve longer reading distance, when compared to a conventional low voltage RFID circuit, simulation results are given to verify the circuit.