Application of Cubic Spline Interpolation and Near-Field to Near-Field Transformation in Spherical Near-Field Undersampled Measurement

Spherical near-field measurement is widely used in antenna measurement due to its advantages of high safety, strong anti-interference capability, and applicability to a wide range of antenna types. However, the measurement process takes a relatively long time because in general the probe needs to scan the entire spherical surface according to sampling criteria. To improve measurement efficiency, a method of spherical near-field undersampling is proposed. Nevertheless, since the sampling criteria are not met in this case, the testing accuracy is not ideal. To address this issue, we combine cubic spline interpolation with spherical near-field to near-field transformation to recover near-field data that satisfies the sampling criteria from undersampled near-field data. Subsequently, the far-field pattern is obtained through spherical near-field to far-field transformation. Simulation results confirm the correctness and effectiveness of the proposed method.