Scalable Near-field Fed Far-field UHF RFID Reader Antenna for Retail Checkout Counters

This paper presents a scalable ultra-high-frequency (UHF) radio frequency identification (RFID) reader antenna for retail checkout counters. The antenna's simultaneous near-field and far-field operation enable effortless and reliable asset identification. Two meandered microstrip lines that are 90°-of-phase form the near-field antenna rim around a far-field patch antenna. The patch antenna is fed by those meandered lines along the vertices on its orthogonal points, resulting in circular polarization. The near-field radiation is evenly distributed with no surface dead zones, and the far-field radiation pattern is symmetrical with a 90° half-power beam-width in both azimuth and elevation planes. The antenna operates in the North American UHF RFID band (902-928 MHz) with a 50 MHz impedance bandwidth. The antenna's gain and axial ratio at the band's center frequency of 915 MHz is 3.3 dBi, and 1.4 dB, respectively. This antenna is low-profile, low-cost and recyclable as it is constructed from polyolefin substrate and copper foils.

I. Introduction

UHF RFID is a part of Automatic Identification and Data Capture (AIDC) system which collects information from an object or an individual without needing a manual data entry. Industry associations such as the Advancing Identification Matters (AIM) and RAdio frequency IdentificatioN (RAIN) promote the global adoption for UHF RFID that utilizes the GS1 UHF Gen2 protocol as per ISO/IEC 18000-63 standard. The industry 4.0 focus on automation of manufacturing and data management demands the need for UHF RFID along with other Internet-of-Things (IoT) devices. A typical UHF RFID system consists of a reader and antenna to transmit and receive RF signals, a tag with a unique identifier, and a computer with appropriate software to post-process the data.