Compact Spherical Near-field Scanning System for Antenna Radiation Pattern Measurement

This paper presents a compact spherical near-field (NF) scanning system and near-field to far-field (NF-FF) transformation for antenna radiation pattern measurement. The low-cost stepping motors together with the Arduino controller R3 model are efficiently employed. The NF data of the antenna under test (AUT) is collected by using a dual-polarized circular open-ended waveguide probe. MATLAB graphic user interface (GUI) is implemented to control the NF scanner and interface to the network analyzer. NF-FF transformation algorithm is implemented by using the spherical wave expansion with numerical integration. The evaluation of an associated double integration in the proposed NF-FF transformation is performed by using the trapezoidal rule numerical integration instead of the conventional fast Fourier transform (FFT) algorithm. Validation, FF radiation patterns of AUT from the proposed system, and simulated far-field radiation pattern are compared. It is found that the simulated FF radiation pattern and the radiation pattern from the proposed system are in good agreement. The proposed system requires less measurement space and a low-cost RF anechoic chamber room compared with the conventional FF radiation pattern measurement technique.