Beam Scanning UHF RFID Reader Antenna with High Gain and Wide Axial Ratio Beamwidth

Abstract

A novel ultra-high-frequency (UHF) RFID reader antenna with 2 dimensional (2D) beam-scanning capability and a wide 3 dB axial ratio (AR) beamwidth of over 136 • is presented. The proposed antenna consists of three concentric metal rings, each having a branch wire to stimulate circular polarization (CP) and a separate feed. The antenna is able to perform a 2D beam-scan with a relatively stable gain (9-11 dBic) from 0 • to 360 • in azimuth, and-40 • to 40 • in zenith. The minima of the antenna's AR beamwidth follows the peak gain direction, giving an equivalent 3 dB AR beamwidth of 136 • for every phi cut, wider than current state-of-the-art [1]. Moreover, the proposed antenna array presents a 50Ω impedance with no impedance matching network, and requires only two phase shifters to steer, significantly reducing the design complexity. The antenna's-10 dB return loss bandwidth is from 843 MHz to 880 MHz, covering the lower band UHF RFID frequencies in the European Telecommunications Standards Institute (ETSI) region.

A UHF RFID Reader Antenna with Tunable Axial Ratio and Fixed Beamwidth

“…In [5], we proposed an antenna with two dimensional (2D) beam-steering abilities, a wide AR beamwidth of 136 • and have shown that its AR minima follows its gain maxima. In this work, we show that the antenna is also able to change its axial ratio without affecting the beamwidth or gain.…”

“…2. The radiating layer of the antenna is composed of three concentric copper loops, each with a perturbation line (PL) to stimulate circular polarization [5], [6], [7]. Changing the angle and length of these perturbation elements would affect the AR performance of the antenna.…”

“…A feeding layer is placed between the radiating layer and an aluminium ground plane with a 45 cm diameter. This layer is formed by three elliptic copper arcs placed directly under three copper loops [5]. Their curvatures are the same as their corresponding copper loops above whereas their lengths and heights from the ground plane can be adjusted to achieve a matched impedance of 50 Ω [5].…”

“…As a result, instead of having two current peaks at fixed locations as in conventional loop antennas, in a loop antenna with added perturbation elements, the current peak travels along the antenna. This is analogous to physically rotating the loop antenna around its axis, producing circular polarization [5], [6], [7].…”

A Glimpse to the Future of RFID Technology Guest Editorial of the Special Issue on IEEE RFID-TA 2019 Conference

“…Specifically, an experimental analysis of the effect of high temperature on its performance is described and discussed, showing a significant chip input impedance variation by increasing the surrounding temperature with a consequent read-range reduction. However, the ceramic tag can be detected at a satisfactory distance of 30 cm when employed with temperatures so high as up to 120 • C. A UHF RFID reader antenna capable of 2-dimensional (2D) beamscanning from 0 • to 360 • in the azimuth plane, and 0 • to 40 • in the zenith plane was proposed in [item (21) in the Appendix] by Chen et al They experimentally demonstrated that the antenna 2D beam-scanning ability and the improved AR performance lead to better tag-reading results, improving the percentage of missing tags by up to 21.6% compared to a standard antenna which has a degraded AR and only supports 1D beam-scanning.…”