This article presents a type of miniaturized high-efficiency patch antennas for UHF radio frequency identification (RFID) reader applications based on the composite right-/left-handed (CRLH) negative order resonance. Miniaturization is achieved by using the first negative order resonance (−1st mode). These proposed CRLH resonators are realized by etching gap on the patch surface, which acts as a series left-handed (LH) capacitor as well as an effective radiator, and using metallic screws on the corner as steadying posts while also providing an LH inductor. Different from the traditional mushroom structures, these screws are placed on the two sides or corner of the unit cells allowing unobstructed current and field flowing inside the cavity. This enhances the quality factor and radiation efficiency. In addition, only metallic sheets, screws, and one thin substrate are used in the design, therefore dielectric loss is basically eliminated. Overall, these proposed antennas achieve a miniaturized size, as well as a high gain and radiation efficiency. The radiation characteristics of these RFID antennas are similar to the conventional patch antennas due to the −1st-order operation. Four antennas, including linearly polarized, circularly polarized (CP), frequency-tunable, and polarization/frequency-reconfigurable antennas, are carefully designed, investigated, and experimentally verified. Remarkable agreement has been observed between simulation and measurement. These antennas well cover 902–928 MHz UHF band. RF range tests are carried out for application verification. They demonstrate a compact size, low-cost, low-loss, and high efficiency with easy implementation. The CP antennas exhibit a good bandwidth and an excellent axial ratio in the whole upper semisphere. They have been selected for mass production, which illustrates a good engineering application example of CRLH metamaterial antennas.

中文翻译：

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基于CRLH负阶谐振的小型化RFID阅读器天线

本文介绍了一种基于复合右手/左手 (CRLH) 负阶谐振的用于 UHF 射频识别 (RFID) 阅读器应用的小型化高效贴片天线。小型化是通过使用一阶负阶共振（-1st 模式）来实现的。这些提议的 CRLH 谐振器是通过在贴片表面蚀刻间隙来实现的，该间隙充当串联左手 (LH) 电容器和有效辐射器，并在角落使用金属螺钉作为稳定柱，同时还提供 LH 电感器。与传统的蘑菇结构不同，这些螺钉放置在单元电池的两侧或角落，允许电流和场在腔内畅通无阻地流动。这提高了品质因数和辐射效率。此外，只有金属片、螺丝、并且设计中使用了一块薄基板，因此基本消除了介质损耗。总的来说，这些提议的天线实现了小型化，以及高增益和辐射效率。由于 -1 阶操作，这些 RFID 天线的辐射特性类似于传统的贴片天线。四种天线，包括线极化、圆极化 (CP)、频率可调和极化/频率可重构天线，都经过精心设计、研究和实验验证。在模拟和测量之间观察到了显着的一致性。这些天线很好地覆盖了 902-928 MHz 的 UHF 频段。射频范围测试用于应用验证。它们具有紧凑的尺寸、低成本、低损耗和高效率且易于实施。CP 天线在整个上半球表现出良好的带宽和出色的轴比。它们已被选中进行批量生产，这说明了 CRLH 超材料天线的一个很好的工程应用实例。