An experiment on antenna arrays with randomly spaced elements

An experimental investigation on the planar array with randomly spaced elements was made by using the holey-plate technique. Two sample arrays, each consisting of 210 elements over a circular aperture of about 56 wavelengths in diameter, were tested at 71.25 GHz. The measured sidelobe levels were -12.8 dB and -13 dB, in excellent agreement with the theory which predicted below -12.8 dB with 90 percent probability and -13.3 dB with 50 percent probability. Further, one may consider the pattern in each plane cutting through the antenna as that of a linear random array. Thus one may study the sample distribution of the sidelobe levels of as many linear random arrays as cuts. The results showed a nearly perfect agreement with the theory, despite the fact that in the theory the mutual coupling effect was neglected altogether. This experiment seems to suggest that when the average element spacing is of the order of a few wavelengths or more, the net coupling effect on the pattern of a random array is generally negligible.