MINIATURE CIRCULARLY POLARIZED ANTENNA FOR UHF RFID HANDHELD READER: DESIGN AND EXPERIMENTS

A low-profile circularly polarized (CP) antenna for a handheld Ultra-High Frequency Radio Frequency Identification (UHF RFID) reader is proposed in this paper. The radiating part on the top substrate is composed of three inverted-F elements rotated 120[degrees] around the center of the structure. A power splitting circuit, placed on the bottom substrate, based on a series transmission line feed delivers equal amplitude to the three IFAs with a sequential 120[degrees] phase shift. Both layers are fabricated on low-cost FR4 material. This design has a disk form factor with a compact size of 35 mm circle radius and an 8.6 mm height. The measurement shows good results with [S.sub.11] as lower than -10 dB for the whole band, 3 dB-axial ratio around 110[degrees] (10 MHz of bandwidth), directivity reaching 4.4 dBic, and the total gain of the antenna is 1.9 dBic. In order to validate the proposed antenna performance, a UHF RFID handheld reader is built based on the ThingMagic M6E-Nano module. Different scenarios are investigated to validate the proposed antenna performance in a real environment.