A compact folded-patch antenna with a dimension of 45 mm $\times45$ mm $\times3.2$ mm ( $0.137\lambda \times 0.137\lambda \times 0.0097\lambda$ ) is proposed for on-metal applications. A T-shaped L-probe is employed for feeding the top-loaded radiating folded patch. It is found that good impedance matching can be easily achieved between the tag antenna and the microchip with the use of the T-shaped feeder. Also, the maximum power transmission coefficient can be significantly enhanced from 0.45 to 1. By adjusting some of the design parameters, the tag’s footprint area can be effectively reduced by 50% while maintaining considerably good read performance. The proposed tag antenna can not only radiate efficiently with a high radiation efficiency of 73.8% but also be read from a long read distance of 19 m when placed on a 20 cm $\times20$ cm metal plate with reference to a transmitting power of 4 W EIRP.

中文翻译：

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由 T 形 L 型探针馈送的高效紧凑型折叠贴片天线，用于金属上 UHF RFID 标签设计

尺寸为 45 mm 的紧凑型折叠贴片天线 $\times45$ 毫米 $\times3.2$ 毫米 （ $0.137\lambda\times 0.137\lambda\times 0.0097\lambda$ ) 建议用于金属应用。T 形 L 型探针用于馈送顶部加载的辐射折叠贴片。发现使用T形馈线可以很容易地在标签天线和微芯片之间实现良好的阻抗匹配。此外，最大功率传输系数可以从0.45显着提高到1。通过调整一些设计参数，标签的占用面积可以有效减少50%，同时保持相当好的读取性能。所提出的标签天线不仅可以有效辐射，辐射效率高达 73.8%，而且当放置在 20 cm 的天线上时，还可以从 19 m 的远距离读取。 $\times20$ cm 金属板参考 4 W EIRP 的发射功率。