A broadband ultra-high frequency reader antenna based on magnetic coupling is proposed for radio frequency identification (RFID) near-field applications. The design utilizes four quarter-wave impedance transformer double-side parallel stripline (QDSPSL)-fed dipoles to form a square region to achieve broadband impedance matching and strong and uniform magnetic field distribution. The phases of currents on each dipole are kept same, thus, strong distribution of magnetic can be generated by the antenna. A 200 × 200 × 1.6 mm3 antenna has been fabricated on an FR-4 substrate to fit RFID near-field application. The measured 10-dB impedance bandwidth is 107 MHz (860-967 MHz), which covers the entire UHF RFID frequency band (860-960 MHz). Measured tests on the antenna read range are carried out by observing the feedback received signal strength indication (RSSI) values, exhibiting a large reading region of 140 × 140 mm2 and 100% reading rate within 100 mm for near-field tags.
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