A two probes scanning phaseless near-field far-field transformation technique

TLDR

The authors propose a phaseless near‑field to far‑field transformation that derives the far‑field from near‑field intensity measurements. By simultaneously recording the voltage amplitudes of two distinct probe antennas over a single scanning surface, the method retrieves the near‑field phase via an unknown plane‑wave spectrum and directly computes the radiated field. Compared with existing phaseless techniques, the two‑probe approach eliminates the need for a second scanning surface, enabling use of smaller anechoic chambers, matches conventional measurement times, and demonstrates reliable, noise‑stable performance in extensive numerical tests.

Abstract

An innovative and effective technique to determine the far-field of a radiating system from near-field intensity data is introduced, analyzed, and tested. The approach is based on the simultaneous measurement of the amplitude of the voltages received by two different probe antennas moving over a single scanning surface in the near zone and performs the phase retrieval of the near-field by assuming as unknown the plane wave spectrum of the field. The radiated field is then straightforwardly evaluated. As compared to the existing phaseless measurement techniques, the use of two different probes makes it possible to avoid the need for a second scanning surface and thus allows the use of smaller (and cheaper) anechoic chambers. Furthermore, the measurement time is essentially equal to that required by conventional techniques based on the measurement of the complex near-field. The reliability and the effectiveness' of the approach are investigated and discussed and the key factors affecting its behavior are highlighted. In particular, the relevance of the difference between the plane wave spectra (PWS) of the two probe antennas in ensuring an acceptable reliability of the solution, with respect to the starting point of the procedure, is outlined. Finally, the effectiveness of the approach is confirmed by an extensive numerical analysis, which also shows the stability of the solution against data noise.