Broadband Circularly Polarized Stacked Patch Antenna for Universal UHF RFID Applications

Abstract

SUMMARY A double layer stacked patch antenna with a size of 200 × 200×48 mm 3 is proposed in this investigation. To achieve a broad CP bandwidth that can cover universal UHF RFID applications (840-960 MHz), a slot loaded circular patch antenna fed by an L-shaped probe is designed as the lower layer (main patch), while the top layer (parasitic patch) is a simple circular patch loaded with a cross-slot of dissimilar arm lengths. Besides demonstrating a broad 10-dB return loss bandwidth of 16% (823-966 MHz) and a CP bandwidth (3-dB axial ratio) of 14.0% (837-963 MHz), the proposed antenna also yields maximum gain and minimum radiation efficiency of 8.8 dBic and 85%, respectively, across the universal UHF RFID bands.

Circularly Polarized Suspended Patch Antenna Fed by Modified L-Probe for UHF RFID Reader

“…The impedance bandwidth and the maximum gain achieved by the proposed antenna is the largest among the rest, whereby the larger gain can be associated with larger ground plane. However in terms of the AR bandwidth, this work shows a greater bandwidth when compared to [22] but not [15], [16] and [21]. Even though this work has a smaller AR bandwidth, the advantage can be seen in terms of the simple design.…”

“…Even though this work has a smaller AR bandwidth, the advantage can be seen in terms of the simple design. In [15] and [16], the antenna configurations require multiple slots in the radiating patch, in addition to needing multiple stacked elements to achieve the desired characteristics. The monopole structure in [21] has very low antenna gain.…”

“…Although this design has large bandwidth, involvement of multiple slots may complicate the fabrication process. An L-shaped probe was deployed for exciting two slot-loaded circular patches in [16]. In this case, the two patches are stacked for achieving a CP bandwidth of 14.2%.…”