<p>在复杂多变的通信环境中，圆极化天线具有抗多径干扰能力强的特点，因此研究并设计圆极化天线具有重要的意义。设计了三款微带宽带圆极化天线，并对宽带特性以及圆极化特性进行了研究分析，具体内容如下：</p> <p>设计了一种毫米波N258频段宽带圆极化天线。以方环单极子天线为基础，上表面的&ldquo;C&rdquo;环形结构以及阶梯馈电能够产生谐振扩展带宽；下表面为带有两个微扰结构的接地板，通过调节天线表面电流横纵比实现圆极化波辐射。仿真结果表明，该天线的阻抗带宽为63.8%(15.39-29.83GHz)，圆极化轴比带宽为47.38%(17.78-28.82GHz)，完全包含N258频段，且峰值增益达到4.46dBi。</p> <p>设计了一种毫米波FR2频段超宽带圆极化阵列天线。顶层的&ldquo;C&rdquo;型辐射结构和底层的馈电结构能够产生高频谐振扩展阻抗带宽并辐射圆极化波。仿真与测试结果表明，天线阻抗带宽为81.25%(19.21-45.50GHz)，圆极化轴比带宽为60.2%(20.59-38.33GHz)，具有超宽带圆极化性能，峰值增益为4.2dBi。为了完全覆盖FR2频段，组成2&acute;2顺序旋转馈电天线阵列，每个单元相位相差90&deg;馈电，仿真结果表明阻抗带宽为99.5%(19.21-56.89GHz)，圆极化轴比带宽为132%(12.29-60GHz)，完全包括FR2频段，峰值增益达到10.72dBi。</p> <p>设计了一种340 GHz亚毫米波大气窗口频段的超宽带圆极化天线阵列。以方环单极子天线为基础，上表面采用&ldquo;?&rdquo;型结构，下表面由改进后的带有三角微扰接地结构组成，通过产生谐振扩展阻抗带宽而且控制了电流的纵横比产生圆极化波；采用2&times;4天线阵列不仅提高了天线增益，而且增强了其方向特性。仿真结果表明该阵列天线阻抗带宽为67.42%(193.86-391.02GHz)，圆极化轴比带宽76.19%(193.68-432.09 GHz)，峰值增益达到15dBi。</p> <p>设计的三款毫米波N258频段、FR2频段和亚毫米波340GHz大气窗口频段的圆极化天线，工作带宽均超过40%，与现有圆极化天线相比带宽优势明显，为高性能微带宽带圆极化天线设计提供了重要的思路。</p>

<p>In the complex and changeable communication environment, circularly polarized antenna has the characteristics of strong resistance to multipath interference, thus research and design of circularly polarized antennas has significant importance. Three microstrip broadband circularly polarized antennas are designed, the broadband characteristics and circular polarization characteristics are studied and analyzed. The main work contents are as follows:</p> <p>A broadband circularly polarized antenna operating in the millimeter-wave N258 band is designed. Based on a square-ring monopole antenna, the impedance bandwidth is extended by incorporating a &ldquo;C&rdquo;-shaped structure on the upper surface and a stepped feed. The lower surface consisted of a ground plane with two perturbation structures, enabling circularly polarized wave radiation by adjusting the transverse-to-longitudinal current ratio on the antenna surface. Simulation results that the antenna has an impedance bandwidth of 63.8% (15.39-29.83 GHz) and an axial ratio bandwidth of 47.38% (17.78-28.82 GHz), fully including the N258 band, with a peak gain of 4.46 dBi.</p> <p>An ultra-wideband circularly polarized antenna array operating in the millimeter-wave FR2 band is designed. The top layer features a &ldquo;C&rdquo;-shaped radiating structure, the bottom layer features a feed structure generating high-frequency resonant extended impedance bandwidth and radiating circularly polarized waves. Simulation and measurement results show that the antenna has an impedance bandwidth of 81.25% (19.21-45.50 GHz) and an axial ratio bandwidth of 60.2% (20.59-38.33 GHz), having wideband circular polarization performance with a peak gain of 4.2 dBi. To fully cover the FR2 frequency band, a 2x2 sequentially rotated feed antenna array is designed, with each element being fed with a 90&deg; phase difference. Simulation results show that the impedance bandwidth reaches 99.5% (19.21-56.89 GHz), and the axial ratio bandwidth reaches 132% (12.29-60 GHz), fully including the FR2 band. The antenna array achieves a peak gain of 10.72 dBi.</p> <p>A submillimeter wave 340 GHz atmospheric window band ultra-wideband circularly polarized antenna array is designed. Based on the square ring monopole antenna, the upper surface features a &ldquo;?&rdquo; structure, and the lower surface is composed of an improved structure with triangular perturbation, they can generate resonance to expand the impedance bandwidth and control the transverse-to-longitudinal ratio of the current, circularly polarized wave can be generated; Adopting 2&times;4 antenna array not only improves the antenna gain, but also enhances its directional characteristics. The simulation results show that the impedance bandwidth of the array antenna is 67.42% (193.86-391.02GHz), the circular polarization axis ratio bandwidth is 76.19% (193.68-432.09 GHz), and the peak gain reaches 15dBi.</p> <p>The three circularly polarized antennas designed in the thesis in the millimeter wave N258 band, FR2 band, and sub millimeter wave 340GHz atmospheric window band all have operating bandwidths greater than 40%, which has a significant bandwidth advantage compared to existing circularly polarized antennas, providing important ideas for the design of high-performance microstrip broadband circularly polarized antennas.</p>

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