Planar near-field measurement of low directivity embedded antennas using a synthetic array probe technique

One of the limitations of planar near-field measurement using conventional processing is the inability to test small antennas with typically less than two wavelengths aperture dimensions because of the excessive ripple errors. This ripple is caused by discontinuity of the measured field at the edge of the plane of measurement which causes the generation of equivalent line sources which produce their own radiation pattern after transformation into the far-field. The ripple can also be viewed as resulting from a spectral domain convolution of the scan window and the antenna aperture field which contains a singularity. The technique presented here reduces the near-field level at the edges of plane of measurement by combining near-field data points to form a directive synthetic array of probes. This allows using the planar measurements for measuring antennas embedded in a large structure without rotating these structures or collecting excessively large scan data points. The deconvolution of the array factor in the spectral domain will be independent from the probe correction. The disadvantage of this processing is the limited measurement angular range in which the processed data are valid.