Multi-spectral representation of measurement probes for antenna field transformations

Measurement probe correction is essential for accurate transformations of near-field antenna measurements. Common measurement probe correction techniques are based on spectral or modal representations of the probe receiving or transmitting behavior. The corresponding field transformation requires that no equivalent sources of the antenna under test (AUT) are within the minimum sphere of the measurement probe and often the minimum spheres of the AUT and the measurement probe antenna should not even overlap. Especially for electrically large measurement probes, these restrictions can prevent small enough measurement distances. If field transformations are possible, electrically large measurement probes may cause reduced efficiencies of the employed transformation algorithm. These limitations are overcome by generating multi-spectral representations of electrically large measurement probes, where individual spatial subdomains of the probe have its own spectral or modal representation. The multi-spectral models are integrated into the fast irregular antenna field transformation algorithm (FIAFTA) and transformation results are shown.