A novel and simple antenna applicable to active RFID tags is designed. The designed antenna has been skillfully integrated with the active RFID tag circuit. The antenna consists of two parts. One part comprises stacked shorted patches and a ground plane. The other one is an active tag circuit mounted on the bottom of the antenna. By using the offset shorting posts technique, the proposed antenna can achieve an enhanced operating bandwidth with a small size. The measurement results reveal that the antenna has return loss less than -10 dB within the bandwidth of 42 MHz (from 914 MHz to 956 MHz), which totally covers the 5MHz bandwidth from 920MHz to 925 MHz (The band is also allowed for passive RFID) requirement for active RFID in China.
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