De-embeding the effect of a printed array of probes on planar very-near-field measurements

This article presents the methodology for de-embedding the effect of a printed array of probes in a planar very-near-field measurement system. The effect of the individual probes and their feed lines is de-embedded using a proprietary calibration process. Then, the effect of the large printed array on the field distribution around the antenna under test (AUT) is estimated using a combination of simulation and measurement data. Finally, in order to counter-act the loading of AUT by the scanner board, an empirical approach is undertaken. Around 50 reference antennas and 1000 measurement points are used in the process and the difference between efficiency values measured in an anechoic chamber and EMSCAN´s RFxpert system were used to de-embed the loading effect of the scanner on the AUT. Consequently, the corrected measurement results exhibit a standard deviation of 1.5dB below 1GHz and less than 1dB above 1GHz.