UHF RFID Reader Antenna With a Wide Beamwidth and High Return Loss

A compact circularly polarized antenna with a wide beamwidth and high return loss (RL) is presented. The antenna consists of four U-shaped metal strips sequentially rotated and fed with a 90 ° phase difference feed network located beneath the ground plane. The antenna is designed to operate at around 915 MHz for UHF radio frequency identification applications, and the experimental results show that it has a wide beamwidth of over 114 ° and high RL of over 34 dB in the 902-928 MHz range.