A Compact Low-Profile Ring Antenna With Dual Circular Polarization and Unidirectional Radiation for Use in RFID Readers

Zhimeng Xu,Zhizhang Chen,Jiade Yuan,Shiji Wu

doi:10.1109/access.2019.2939271

Zhimeng Xu, Zhizhang Chen + Show 2 more

Open Access

https://doi.org/10.1109/access.2019.2939271

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Journal: IEEE Access	Publication Date: Jan 1, 2019
Citations: 12	License type: CC BY 4.0

Affiliation: Fuzhou University, Dalhousie University

Abstract

A compact low-profile square ring antenna with unidirectional radiation and dual circular polarization (CP) is proposed for uses in radio frequency identification (RFID) readers. A small size conducting plane are slotted and placed underneath the ring antenna as a reflector to achieve low profile and unidirectional radiation. A branch line coupler is meandered inside the ring radiator to save space and generate dual circular polarization. Four inverted L-shaped strips are introduced to overcome the negative effects of tight coupling between the radiator and reflector. The measured -10 dB impedance bandwidth of |S 11 |, 3 dB axial ratio (AR) bandwidth and maximum gain are of 850-1060 MHz, 876-1084 MHz and 5.62dBi, respectively. The lowest measured gain values in RFID band of 900-930 MHz is 4.54dBi and the overall size is 0.31 λ 0 ×0.31 λ 0 ×0.034 λ 0 (λ 0 is denoted the wavelength at center frequency). The proposed antenna has not only the lowest profile but also the best overall performances. It is an excellent antenna that can be fitted where there is a limited space in RFID system.

Highlights

Radio frequency identification (RFID) systems are widely used in object tracking, product manufacture, sales, logistics, etc [1]–[3]
The microstrip ring antenna is the better candidate since its side length is about one quarter-wavelength and one half of the conventional patch antenna [4]–[6] when they both operate at its fundamental mode
A compact low-profile dual circularly polarized ring antenna with unidirectional radiation has been developed for radio frequency identification (RFID) applications

Summary

INTRODUCTION

Radio frequency identification (RFID) systems are widely used in object tracking, product manufacture, sales, logistics, etc [1]–[3]. Its antenna is expected to have unidirectional radiation, circular polarization, high gain and be of low-profile; they ensure reliable communications between RFID tags and readers and small form factors, light weights and compactness. J. Yuan et al.: Compact Low-Profile Ring Antenna With Dual CP and Unidirectional Radiation for Use in RFID Readers. In [16], a wideband low-profile unidirectional antenna with profile height of 0.16 λ0 is obtained using the resonance-based reflector; the profile heights are still relative larger, which cannot fully meet the requirements for future compact RFID devices. A novel low-profile square ring antenna is developed with introduction of a slotted conducting plane as the reflector to generate unidirectional radiation. The proposed antenna has a smaller form factor than the existing antennas and is very suitable for limited space-restrain RFID devices

ANTENNA CONFIGURATION

ANTENNA DESIGN AND ANALYSIS

DUAL CIRCULAR POLARIZATION

EXPERIMENTAL RESULTS AND DISCUSSIONS

CONCLUSION