Electromagnetic (EM) Spherical Near-Field Interpolation Using Discrete Cosine Transform (DCT) techniques

This study focuses on electromagnetic (EM) spherical near-field interpolation employing discrete cosine transform (DCT) techniques. DCT techniques are employed to mitigate the effects of under-sampling in near-field (NF) data on errors in far-field (FF) antenna radiation patterns. The NF-FF transformation algorithm utilizes spherical wave expansion with double numerical integration. In this research, under-sampled NF data from a seven-patch array antenna are simulated using CST Microwave Studio, with sampling angles exceeding the maximum criteria set by the NF spherical sampling theorem. The study finds that the DCT technique is highly effective compared to the FF radiation pattern obtained from CST MWS under a 25.65% under-sampling rate. Moreover, the absolute error of the FF radiation pattern is less than 12% in the XZ plane and less than 4% in the XY plane, respectively. Under-sampling NF data can significantly reduce the time required for NF data acquisition. It is crucial to select an appropriate error reduction method for NF data to minimize errors in FF antenna radiation patterns.