Design of a 2.45 GHz passive transponder using printed dipole rectenna for RFID application

In this paper, we designed a passive RFID transponder at 2.45 GHz. The printed dipole antenna with wider bandwidth than that of the conventional patch antenna is suggested. The slot of the printed dipole could find accurate matching point and improve the antenna gain. According to the measured results, the gain of the antenna was 2.38 dBi and the conversion efficiency of the detector was 40.3% at the load resistance of 3.2 k/spl Omega/. The transmitted power from the reader is 500 mW (27 dBm) and the gain of the reader antenna is 14.57 dBi. The received power was 1.51 mW (2.2 V, 687 /spl mu/A) at the distance of 1.5 m from the reader. Also we suggest an ASK modulation method using a bipolar transistor to compensate the disadvantage of the conventional PIN diode, which needs large current.