Compact circularly polarized circular microstrip tag antenna mountable on metallic surface

Abstract

the whole operating bandwidth, and a peak value appears at 67.5 GHz.Simulated E(yz)-and H(xz)-plane radiation patterns at 40, 50, 60, and 70 GHz are shown in Figure 4. It can be observed that the antenna can present unidirectional radiation patterns with very small backward radiation. The E-plane SLL is always kept small, but the H-plane SLL is slightly distorted due to the radiation of the currents on the vertical walls of the stairs and the connector. If judged by the SLL, the bandwidth can still cover a frequency band from 30.6 to around 70 GHz. Because of the same reason, the cross-polarization over the whole operating frequency band is around À10 dB.Measurements of the radiation patterns are performed from 50 to 75 GHz due to limitation of the in-house measurement system. Meanwhile, measurements are done in the upper half plane, i.e., 0 y 90 , because of the same reason. Figure 5 gives comparisons between the simulated and the measured radiation patterns at 50, 60, and 70 GHz. In the figure, simulations agree well with measurements, especially in terms of the copolarization patterns, proving the validity of all simulations in this article. As far as the cross-polarization is concerned, the measured results are larger than the simulated ones by around 5 dB. CONCLUSIONA wideband mm-wave CBA is studied in this article, and its RBD exciter is fabricated on a substrate along with the feeding network. With the help of the elliptical composite cavity and the RBD exciter, a maximum operating bandwidth covering 30.6-70 GHz and a broadside gain of 8.2-11.8 dBi can be achieved for SWR 2 and stable radiation patterns. This antenna can also be easily scaled upwards to higher frequencies due to its large electrical dimensions and no extremely fine structures in this design. Meanwhile, it is also suitable for integrated mm-wave system applications, in which integrated transceiver can be placed at the vertexes of the RBD or on the microstrip line. ACKNOWLEDGMENTS ABSTRACT:A compact circularly polarized circular microstrip tag antenna designed for RFID UHF band is presented. The proposed tag antenna is excited by using microstrip-line coupling-feed method. By choosing the proper lengths of two short-circuited arc microstrip lines and its coupling distance, good complex impedance matching can be obtained. Moreover, a cross slot of unequal arm lengths embedded in a circular patch is used to achieve compact circularly polarized operation. The measured 10-dB return-loss bandwidth of the tag antenna is 40 MHz (901-941 MHz), while the 3-dB axial-ratio bandwidth is 6 MHz (912-918 MHz). Further experiment shows that the Figure 5 Results for signal s 4

Linearly tapered meander line cross dipole circularly polarized antenna for UHF RFID tag applications

“…Table demonstrates comparison among the proposed antenna and previously reported circularly polarized antennas in terms of the maximum read range, antenna size, 3 dB axial ratio bandwidth, and gain. The read range of the antennas reported in References and are computed with circularly polarized readers having EIRP of 4 W and in Reference , 3.28 W EIRP has been used. The proposed cross dipole antenna has smaller 3 dB axial ratio bandwidth but size of the antenna is also smaller except for References and .…”

“…Square microstrip CP tag antennas, with unequal cross slots, fed by a coupling feed line have been proposed in References and . A circularly polarized circular microstrip antenna is presented in Reference with cross slot and coupling feed technique. Although the antennas reported above exhibit circularly polarized radiation on a metallic surface with longer read range, the use of shorting pins in the coupling feed lines makes the antenna structures complicated for fabrication.…”

“…A circularly polarized circular microstrip antenna is presented in Reference with cross slot and coupling feed technique. Although the antennas reported above exhibit circularly polarized radiation on a metallic surface with longer read range, the use of shorting pins in the coupling feed lines makes the antenna structures complicated for fabrication. Furthermore, a compact circularly polarized structure of UHF RFID tag antenna has been presented by Lu and Chang in Reference by introducing a Y‐shaped slit and two orthogonal N‐shaped slits to provide wider half power operating bandwidth (135 MHz); but the obtained 3‐dB AR bandwidth is less than 10 MHz.…”

Dual-Band Uhf Rfid Tag Antenna Using Two Eccentric Circular Rings

“…The arc-shaped short-circuited microstrip-line structure consisting of the microchip (at an angle β = 22 • with the x-axis) is used to excite the two rings simultaneously by coupling feed technique. It has been reported in the literature [16] that in coupling feed technique, the impedance of a tag antenna is contributed by the total length, width of the microstrip-line feeding structure and also the coupling distance between microstrip line and patch. The reactive part of the tag antenna impedance is mainly determined by the inductive reactance of the short-circuited microstrip line.…”

“…The outer ring resonates at 866 MHz, and the inner ring resonates at 956 MHz (catering to the RFID bands used in Europe and Japan respectively), hence providing dual-band response. The two rings are simultaneously excited by the arc-shaped feeding strip with the IC chip using microstrip-line coupling method [16]. The input impedance of conventional microstrip antennas is usually designed to match the 50 Ω impedance of the traditional feeder.…”