Miniaturized RFID/UWB Antenna Structure that Can be Optimized for Arbitrary Input Impedance

This paper presents a novel planar antenna structure with miniaturization capability that fits in a small area, and which can be designed towards any arbitrary input impedance, for RFID applications. The proposed antenna has three main parts: the feeding loop, the extension parts that work mainly as the radiator, and the connection between these parts. This antenna structure can be integrated with RFID tags to increase the reading range of the tags. A sample antenna set containing one scavenging antenna at 915 MHz for wireless powering, and one UWB antenna at 5.5 GHz with a 500 MHz bandwidth, were designed with the proposed antenna structure to be used in an RFID/UWB tag. This antenna set occupied an area of 11 × 18 mm². It achieved a measured reading range of 110 cm, for a realized gain of -16 dBi. The radiation pattern of the proposed antenna, integrated with an RFID chip, was measured and compared with simulations in the E and H planes, showing good agreement.