Specific character of the focusing method for the measurement of the radiation patterns of planar phased arrays

The paper assesses the limits of the application of the focusing method for measuring the radiation patterns of planar phased arrays. In this method, measurement in the far field is replaced by measurement of the angular dependence of the field in the focal region, and focusing is achieved by an additional phasing of currents, leading to the synphase summation of their fields at a finite distance. It is shown that the pattern and field difference in the focus becomes small if the focal point is located at a distance 1.5 to 2 times greater than the size of the antenna.