A small RFID tag antenna in a UHF band is proposed in this article. Using dual resonance, the antenna has bandwidth‐enhanced characteristics without an additional matching circuit. The meander shape of the proposed antenna helps to reduce the antenna size. The bandwidth of the antenna is enhanced by two radiators that create dual resonance in adjacent frequencies. When the length and location of each radiator are adjusted, the antenna can make dual resonance at an arbitrary impedance point, thereby enabling the antenna to match an RFID tag chip in a wide frequency range. According to the simulated and measured results, the proposed antenna has almost double the bandwidth of a regular antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2027–2031, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23576

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broadside radiation patterns are observed, and the cross-polar levels are below Ϫ18 dB in both the E-and H-planes. The backward radiation is below Ϫ15 dB for both ports. The radiation patterns are also measured at other frequencies, and it is observed that the radiation patterns are stable across the bandwidth. The results are omitted here for brevity. CONCLUSIONA broadband dual-polarized antenna has been proposed. By using only one patch, the designed antenna achieves a broad bandwidth over 17%, isolation below Ϫ32 dB, and is simple in structure. This antenna could be used in the base stations of dual-polarization telecommunication systems, for example. Compared to previous designs using stacked patches (see, for example, [9]), the proposed design is simpler in structure and lower in cost. Compared to previous designs using a single patch (see, for example, [10]), it has one important advantage: it can make good use of the space on both sides of the ground plane, as the feed circuits for two orthogonal polarizations are placed on each side of the ground plane, respectively. This can double the space for accommodating active and passive circuits, and will be attractive for array applications, for example, dual-polarized passive or active arrays, where space in the feed-network layer presents a significant problem, as many components (including active circuits, phase shifters, filters, and so forth) need to be accommodated in the feed layer. The space available at each polarization port can also be used to accommodate polarization-switching circuits for polarization-agile or polarization-diversity antenna applications.