A Probe Correction Technique for Near Field to Far Field Transform Based on Sources Reconstruction Method

The sources reconstruction method (SRM) is widely applied to antenna measurement, antenna diagnostics and imaging, etc. It is a near field to far field transform, which utilizes near-field data to determine an equivalent magnetic current source over a fictitious flat surface enclosing the antenna under test. But the existing SRM is low in accuracy, since it does not have a proper probe correction algorithm. First, this paper introduces an integral equation connecting the equivalent magnetic current and the signal received by the probe according to the reciprocity theorem. Secondly, the integral equation is converted to a matrix equation by the method of moments and the magnetic current is determined by solving the matrix equation. Finally, the magnetic current leads to the pattern of the antenna under test readily. As an example, a horn is measured with a wave-guide probe and the receiving signals are processed by the proposed method to obtain the pattern, whose root mean square errors (RMSE) are only 1/3 of those of the pattern obtained by the SRM without probe correction. Therefore, the proposed probe correction algorithm is accurate and effective for the SRM.