A broadband microstrip patch antenna fed through vias connected to a 3dB quadrature branch line coupler for worldwide UHF RFID reader applications

摘要

This paper presents the design of a circularly polarized Radio Frequency Identification (RFID) reader antenna for worldwide Ultra High Frequency (UHF) (860–960 MHz) applications. The proposed antenna, which consists of a microstrip patch with truncated corners and a cross slot, is suspended over a ground plane and fed through vias that extend from the quadrature 3 dB branch line coupler placed below the ground plane. This antenna has a total size of 225 × 250 × 12.8 mm3 and shows a measured matching band of 840–1150MHz (31.2%) and 3 dB axial ratio (AR) of 820–1120 MHz (31%).