Dielectric-Loaded End-Fire Slot Antenna With Low Back-Lobe Radiation for UHF RFID Applications

In this paper two end-fire constant width slot antennas built over an FR4 substrate are presented for UHF RFID tracking systems (902-928 MHz). The antennas are fed by a CPW to slot-line transition tuned to 915 MHz. Dielectric loading is implemented as a way to reduce the half-power beamwidth (HPBW); specifically, variations in the FR4 substrate thickness and additional loading material are used to achieve a 3 dB beamwidth of 75 degrees, which is an improvement of 55 degrees compared with the 130 degrees HPBW when no loading is applied. Corrugated edges provide front-to-back ratio enhancement, achieving a ratio of 17.74 dB compared to 10.7 dB with no corrugation.