一种低交叉极化小口径超宽带天线的设计

Design of a Miniature Ultra-Wideband Antenna with Low Cross Polarization

在高精度近场法天线测量、平面波发生器应用等场合,工作频段通常受限于近场探头。为了克服开口波导探头的带宽限制,出现了基于Vivaldi天线的超宽带、小口径天线作为近场探头。然而,常见的Vivaldi天线是非对称结构,导致交叉极化性能较差。设计了一款低交叉极化小口径超宽带天线,采用5层对称结构改进了传统Vivaldi天线的非对称性,利用贝塞尔曲线设计渐变槽辐射结构、加载电阻和贴片以及刻蚀矩形斜槽,减小了交叉极化比和天线驻波,改善了天线辐射方向性图。该探头口径宽70 mm、长201 mm,在0.9~6 GHz频段内天线仿真所得交叉极化比优于40.9 dB,增益为-5.5~9.53 dBi,端口反射系数幅度低于-10 dB,其辐射方向性图在全频段不开裂、主波束指向不变。

In applications such as precise near field antenna measurements and plane wave generator,the operating frequency is often limited by the bandwidth of the near-field scanning probe.To overcome the bandwidth limitation of open-ended waveguide probes,Ultra-Wideband(UWB)small aperture antennas based on Vivaldi antennas have been developed.However,their cross polarization performance is poor due to their common asymmetric structure.To address this issue,a miniature UWB antenna with low cross polarization is proposed in this paper.A 5-layer symmetrical structure is used to improve the traditional asymmetric Vivaldi antenna,and a Bezier curve is employed to design the gradient slot radiation structure.Loading resistance,patch,and etching rectangular chutes are also used to reduce the antenna standing wave and improve radiation directivity.The proposed antenna has an aperture width of 70 mm and a length of 201 mm.In the 0.9-6 GHz frequency band,the simulated cross polarization ratio of the antenna is better than 40.9 dB,and the gain is between−5.5 dBi to 9.53 dBi.The port reflection coefficient amplitude is less than−10 dB,and the radiation pattern is smooth,symmetrical,and without pits across the entire frequency bandwidth.