A universal UHF near-field RFID reader antenna with wide bandwidth and adjustable reading area

A universal ultrahigh-frequency (UHF) near-field radio-frequency identification (RFID) reader antenna with wide bandwidth and adjustable reading area is proposed in this letter. The antenna consists of an inverting power splitter base on double-sided parallel stripline and adjustable traveling-wave near-field radiation units, which consists of two symmetrical meander microstrips and a complementary open resonant ring loaded on the ground plane. A design example with three radiation units is simulated, fabricated, and tested for verification. The result indicates that the proposed antenna has the 10-dB impedance bandwidth of 128%, which completely covers the universal UHF RFID band from 840 to 960 MHz. The 100% read-write rate is achieved within the read-write distance of 10 mm according to the reading test. The reading area of 731 x 120 mm(2) can be obtained for increasing the number of radiation units to 10. Moreover, the antenna features low far-field gain, low-cost, strong and uniform magnetic field distribution. Therefore, the proposed antenna and design method have good application prospects in the Internet of Things.