Broadband circularly polarized stacked patch antenna for universal UHF RFID applications

Abstract

A double layer stacked patch antenna with a size of 200 × 200×48mm3 is proposed in this investigation. To achieve a broad CP bandwidth that can cover universal UHF RFID applications (840-960 MHz), a slot loaded circular patch antenna fed by an L-shaped probe is designed as the lower layer (main patch), while the top layer (parasitic patch) is a simple circular patch loaded with a cross-slot of dissimilar arm lengths. Besides demonstrating a broad 10-dB return loss bandwidth of 16% (823-966 MHz) and a CP bandwidth (3-dB axial ratio) of 14.0% (837-963 MHz), the proposed antenna also yields maximum gain and minimum radiation efficiency of 8.8 dBic and 85%, respectively, across the universal UHF RFID bands.