The design of a miniaturized frequency-tunable circularly polarized twin dual folded inverted-L antenna with varactor-loaded split-sing resonator structure is proposed in the paper. The design integrates two linearly polarized inverted-L antenna elements with double-folded arms and with a split-ring resonator (SRR) structures on both sides. To improve the impedance matching and radiation characteristics the double-folded structure plays a significant role. Although the use of SRRs to the dual inverted-L antenna elements achieves compact volume, the antenna's radiation efficiency rapidly decreases around the SRR's resonant frequency. The decrease is avoided by employing a variable capacitance diode loaded on both SRR structures (dual folded inverted-L antenna, VLSRR). The antenna structure is minimized to be about 66 mm in length, 10 mm width, and 1 mm in height (66 × 10 × 1 mm³). The configuration is simplified by using wave feeding. The better values are obtained between the theoretical calculations and simulated results, which validate the design concept and have a wide varactor tuning bandwidth. The simulated and measured results show that the proposed antennas resonate at multiband frequencies: Band 1 (3.28–3.70 GHz) with varactor tuning of 425 MHz; Band 2 (6.42–6.75GHz) with varactor tuning of 331 MHz; and Band 3 (13.75–14.21 GHz) with varactor tuning of 463 MHz, with the impedance bandwidth of 6%, VSWR < 2, and 3-dB axial ratio (AR) < 3 across the entire operating bands.

中文翻译：

---

具有变容负载开环谐振器结构的频率可调圆极化双折叠倒L天线

提出了一种微型可调频率圆极化双折叠倒L型天线的设计，该天线具有加载变容二极管的分裂单谐振器结构。该设计集成了两个具有双折臂的线极化倒 L 形天线元件，并在两侧具有裂环谐振器 (SRR) 结构。为了改善阻抗匹配和辐射特性，双折叠结构起着重要作用。尽管在双倒 L 天线元件上使用 SRR 可以实现紧凑的体积，但天线的辐射效率在 SRR 的谐振频率附近迅速下降。通过采用加载在两个 SRR 结构（双折叠倒 L 形天线，VLSRR）上的可变电容二极管来避免这种降低。天线结构最小化到长度约为 66 毫米，³）。通过使用波馈简化了配置。理论计算与仿真结果之间取得了较好的数值，验证了设计理念并具有较宽的变容二极管调谐带宽。仿真和测量结果表明，所提出的天线在多频带频率下谐振：频带 1（3.28-3.70 GHz），变容二极管调谐为 425 MHz；频带 2 (6.42–6.75GHz)，变容二极管调谐为 331 MHz；频段 3 (13.75–14.21 GHz)，变容二极管调谐频率为 463 MHz，阻抗带宽为 6%，VSWR < 2，整个工作频段的轴比 (AR) < 3。