Scalable Near-Field Fed Far-Field RAIN RFID Reader Antenna for Retail Checkout Counters

Abstract

This article 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° out-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. Fabricated 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. The antenna is pragmatic, scalable with increasing checkout counter sizes and insusceptible to proximity assets and metal frames.