CPW-fed modified rhombus slot antenna with circularly polarized radiation for UHF RFID fixed reader application

摘要

A modified rhombus slot antenna using coplanar waveguide (CPW)-fed is presented. The proposed antenna has circularly polarized (CP) radiation in ultra-high frequency band for radio frequency identification fixed reader application. The antenna comprises a straight strip, a modified rhombus slot with a pair of L-shaped grounded strips and a pair of inverted L-shaped extended slots for exciting CP radiation. In this design, the use of the grounded strip and the extended slot were found an effective approach for exciting two resonant modes as well as achieving CP radiation. The experiment results exhibited the broadband CP characteristics including an impedance bandwidth of 34.7% (694-986 MHz) for 10 dB return loss, a CP bandwidth of 26.3% (860-1120 MHz) for 3 dB axial ratio and maximum gain of 5.4 dBic at 860-960 MHz.