This study presents a novel compact circularly polarized antenna for universal ultrahigh-frequency (UHF) radio-frequency identification (RFID) handheld reader applications. The antenna is composed of a coplanar waveguide (CPW) L-shaped feedline mounted at the right edge of the square slot at the bottom of the ground plane to realize a circular polarization; a horizontal stub protruded from the right side of the square slot towards the slot centre, and a vertical stub is mounted at the lower left of the square slot. The designed antenna printed on one ground plane layer of a low-cost FR4 substrate with an overall size of 120×120×1.6 mm3. The measurement results show indicate that the fabricated antenna achieves a wide axial ratio (AR) bandwidth of 460 MHz (818–1278 MHz), wide impedance bandwidth of 54.6% (630–1103 MHz), and a measured peak gain of 4.0 dBi. The proposed antenna is a good candidate for compact universal UHF RFID handheld reader applications (840–960 MHz).
A compact wideband circularly polarized square slot antenna for universal UHF RFID reader applications is proposed and tested. An L-shaped radiator at lower surface of the substrate is used to feed the proposed antenna. To achieve a broadband circular polarization (CP) and good performance, two rectangular stubs with different sizes are inserted at opposite corners of the square slot at the upper surface of the substrate. A small rectangular slit is used to improve the impedance matching of the proposed antenna. The antenna's measured < 10-dB impedance bandwidth and measured 3-dB axial ratio bandwidth are 70.2% (660-1374 MHz) and 45.8% (796-1269 MHz), respectively. The proposed antenna has a dual circular polarization characteristic, wide impedance bandwidth, wide axial ratio, compact size, and maximum measured gain about 3.9 dBi. The total size of the proposed antenna is 120×120×1.6 mm 3. Furthermore, the impedance bandwidth and axial ratio bandwidth of the proposed antenna cover the entire UHF RFID band easily. The proposed antenna is suitable for UHF RFID reader applications.
A compact wideband circularly polarized (CP) square slot antenna for universal ultra high frequency (UHF) RF identification (RFID) handheld reader applications is proposed, fabricated, and tested. The antenna is coplanar waveguide (CPW) fed by an inverted Z-shaped feeding line. By inserting four stubs in diagonal directions and two inverted T-shaped strips inside the square slot, broadband CP operation, wide axial ratio bandwidth, and good impedance matching are achieved. The measured < −10 dB impedance bandwidth is from 706 MHz to 1007 MHz (301 MHz, 35.1%). The measured 3-dB axial ratio (AR) is 427 MHz (745-1172 MHz, 44.5%). The maximum measured gain of the proposed antenna is 4.8 dBi. The proposed antenna has wide impedance bandwidth, wide axial ratio bandwidth, and small size. The dimensions of the antenna are only 120 × 120 × 1.6 mm 3. The impedance bandwidth and AR bandwidth performances of the proposed antenna can easily cover the UHF RFID band as whole.
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