Enhancement of Radio Frequency Identification Coverage for Various Indoor Scenarios Using Diversified Radiation Patterns of Tag and Reader Antennas

Abstract

This paper proposes a calculation method for determining indoor RFID coverage using an overhead RFID reader antenna. The proposed coverage calculation accounts for the radiation patterns of both the reader and tag antennas, as well as the installation height of the reader antenna. In various application environments with different reader antenna heights, optimizing the radiation patterns of tag and reader antennas is proven to enhance indoor RFID coverage. In simulations, a commercial reader antenna with circular polarization (9 dBic gain, 120° beamwidth) covers a horizontal distance of up to 630 cm when paired with a dipole tag (0 dB gain) and a reader antenna height of 50 cm. Elevating the reader to 250 cm extends coverage to 800 cm. To further improve coverage, a dual-chip RFID tag with adjustable beam separation is utilized, where the beams' separation can be adjusted by varying the spacing between the tag and its metal reflector. In an optimized scenario, coverage extends to 1090 cm and 1380 cm for reader antenna heights of 50 cm and 250 cm, respectively. For additional coverage augmentation, a reader antenna with a quasi-cosecant squared radiation pattern is employed to distribute signal power evenly over the detection area. With this modified pattern and a maximum antenna gain of 4.57 dBic, coverage is further extended to 1400 cm and 1450 cm for reader antenna heights of 50 cm and 250 cm, respectively. The maximum field of view achieved with the quasi-cosecant squared reader antenna and dual-chip RFID tag is 176° and 188.2°, respectively, for reader antenna heights of 50 cm and 250 cm. The findings of this study demonstrate the potential of the proposed calculation method to estimate indoor RFID coverage in various scenarios and optimize antenna radiation patterns for maximum coverage.