A Compact Circular Polarization Antenna Using Folded Ground Elements

Abstract

This communication presents a new antenna structure using a folded ground element (FGE) for a compact antenna implementation. The proposed FGE is analyzed with an equivalent circuit model where equivalent capacitances and inductances of the proposed antenna are included. Also, slot patterns are integrated into a radiation patch element, resulting in a further reduction in the overall antenna size. To verify the proposed antenna with FGEs, an RFID antenna module with a righthanded circular polarization (RHCP) feed network was implemented and tested. The fabricated antenna size was 100 x 100 x 12 mm(3) (0.29 lambda(0) x 0.29 lambda(0) x 0.03 lambda(0) at 868 MHz), showing a significant reduction in size compared to the conventional structures. The measured reflection coefficient for the feed network was better than 10 dB from 610 to 950 MHz, and 3 dB axial ratio (AR) bandwidth was about 137 MHz (817-954 MHz). Also, the measured peak gain and AR at 868 MHz were 4.6 dBic and 0.6 dB, respectively.