Case Study of Sample Spacing in Planar Near-Field Measurement of High Gain Antennas,
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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The near-field measurement technique has been used extensively for electrically large antennas which can not be easily tested on a far-field range. In reconstructing the far-field antenna patterns from the near-field measurements, a planar configuration may be used with a computation based on the Fast Fourier Transform FFT. The near-field data are generally sampled over a planar grid at the Nyquist sampling rate of lambda sub zero2 spacing or less. For electrically large antennas, sampling at the Nyquist rate requires long data acquisition times over which significant system electronic drift may occur. Furthermore, the computer capacity may limit the largest size of the data set. Special data filtering techniques for large data sets have been reported. However, these techniques still require sampling at lambda sub zero2 spacing.