基于等效磁流法的平面近场测量技术研究

Research on planar near field measurement algorithm based on equivalent magnetic current method

为了进一步论证等效磁流法的近场-远场变换算法在平面近场测量中的实用性与准确性,本文首先根据矩量法(MOM)建立了平面天线口径面上等效磁流的辐射电场方程,利用波导探头采集待测天线平面近场的电场分布,通过共轭梯度法求解矩阵方程,得到天线口径面上的等效磁流分布,之后由格林函数计算出天线远场方向图。最后,通过两种喇叭天线进行实验测试验证。同时将等效磁流法计算出的远场方向图以及由传统的平面波展开法计算出的远场方向图与紧缩场天线测试暗室的测量结果进行对比,结果发现本文算法反演出的远场方向图比平面波展开法在相同测试数据下反演出的远场方向图与紧缩场测量结果相比一致性更好,其中线性角锥喇叭天线的E面和H面方向图吻合度均达到140°,双脊喇叭天线的E面方向图吻合度达到140°,H面方向图吻合度达到100°,验证了等效磁流法算法在平面近场测量中的准确性。

In order to further demonstrate the practicability and accuracy of the near-field to far-field transformation algorithm of equivalent magnetic current method in plane near-field measurement. According to the method of moments(MOM), the radiated electric field equation of the equivalent magnetic current on the aperture surface of the planar antenna is established. The waveguide probe is used to collect the electric field distribution of the planar near-field of the antenna to be measured, and then the conjugate gradient method is used to solve the matrix equation to obtain the equivalent magnetic current distribution on the aperture surface of the antenna, and then the far-field pattern of the antenna is calculated with Green′s function. Finally, two types of horn antennas are tested. At the same time, the far-field pattern calculated by the equivalent magnetic current method and the far-field pattern calculated by the traditional plane wave expansion method are compared with the measurement results of the compact field antenna test chamber. The results show that the far-field pattern inversed by this algorithm is more consistent with the compact field measurement results than that inversed by the plane wave expansion method under the same test data. For the pyramidal horn antenna, the radiation pattern shows perfect agreement over ±70° of θ=0° for both E-plane and H-plane. For double ridged pyramidal horn antenna, the radiation pattern has excellent agreement up to ±70° for E-plane, and ±50° for H-plane, which shows acceptable results for the test. The accuracy of the planar near-field measurement using equivalent magnetic current method is verified.