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A novel ultra-high-frequency (UHF) RFID reader antenna is proposed. The antenna has a unique property as being able to change its axial ratio (AR) without affecting its gain, beamwidth or impedance matching performance, enabling the isolated study of the effect of different axial ratios in RFID tag reading.

An Ultra High Frequency (UHF) Radio Frequency Identification (RFID) system using distributed antenna arrays for interrogating RFID tags in a highly multipath environment is demonstrated. The system makes use of phase diversity and beam steering to overcome fading. The tag detection accuracy is compared to a standard fixed antenna system, showing that the presented system is able to deliver more power to the more challenging tags, and therefore is capable of a higher tag read success rate. It is also shown that, whereas a fixed antenna is capable of scanning a single cell, the ability of a phased array to scan through 360° azimuth leads to a reduction in number of antennas required for a multicell system. The experimental results are validated using a 3D field-based propagation model, which enables visualisation of the power distribution in the field of interest, and provides insight into the improved system performance.

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