This communication presents the design of a compact loop antenna with independent frequency tuning. The proposed antenna consists of a feed line fed by a $50~\Omega $ coaxial probe and four resonating arms on the adjacent sides of the feed line. The two outer resonating arms are directly coupled to the feed line and the other two inner resonating arms are coupled to the outer arms. The proposed antenna has a footprint of 25 mm $\times 10$ mm $\times0.2$ mm. The designed antenna operates at 0.9, 2.4, 3.5, and 5.5 GHz. Each of these bands is individually tuned using varactor diodes. Thus, the aggregation of these tunable bands provides wide bandwidth. The impedance bandwidth and percentage bandwidth of the antenna are 270/1000/400/700 MHz and 33%/47.6%/11%/12.7%, respectively. Furthermore, the gain and efficiency of the antenna are 1.7/1.3/2.1/2 dBi and 60%/63%/65%/69%, respectively. The prototype antenna is fabricated and tested. The measured impedance and radiation characteristics of the antenna are in good correlation with the simulation results.

中文翻译：

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用于手持无线设备的具有独立调谐的紧凑型频率可重构天线

该通信介绍了具有独立频率调谐功能的紧凑型环形天线的设计。建议的天线由馈线组成 $50~\Omega $ 同轴探头和馈线相邻两侧的四个谐振臂。两个外谐振臂直接连接到馈线，另外两个内谐振臂连接到外臂。建议的天线占地面积为 25 毫米 $\times 10$ 毫米 $\times0.2$ 毫米。设计的天线工作频率为 0.9、2.4、3.5 和 5.5 GHz。这些频段中的每一个都使用变容二极管单独调谐。因此，这些可调频带的聚合提供了宽带宽。天线的阻抗带宽和百分比带宽分别为270/1000/400/700 MHz和33%/47.6%/11%/12.7%。此外，天线的增益和效率分别为1.7/1.3/2.1/2 dBi和60%/63%/65%/69%。原型天线被制造和测试。测得的天线阻抗和辐射特性与仿真结果具有良好的相关性。