Compact shorted inverted-L antenna with circular polarisation for RFID handheld reader

Abstract

Two shorted inverted-L radiating elements are located on the orthogonal corner of the square substrate and connected to each output port of a Wilkinson power divider. A shorted inverted-T strip is placed on the other corner of the square for a perturbing resonator to generate circularly-polarised (CP) radiation in the UHF band. Proper adjusting of the horizontal and vertical lengths of the inverted-T strip will differentiate two orthogonal linearly modes with 90° phase difference for a good CP radiation. Simulated and measured results indicate that the proposed structure can achieve circular-degree polarisation operation. A measured impedance bandwidth (VSWR ≤ 2) of about 16.4% (810-960 MHz) and a 3 dB axial-ratio (AR) bandwidth of about 4.4% (890-930 MHz) at 915 MHz were obtained. © The Institution of Engineering and Technology 2013.