What is the Nyquist Sampling Frequency for Amplitude-Only Planar Near-Field Tests?

It was claimed in the previous literature that the Nyquist sampling frequency must be doubled in the planar near-filed range if the phase information is not available. This paper discusses the Nyquist sampling interval for the amplitude-only planar near-field test. The spectrums of the complex and phaseless signals in wavenumber domain are discussed and analyzed. The half wavelength is shown to be a sufficient condition for the Nyquist sampling of phaseless planar near-field test, which is experimentally verified.