Range Distance Requirements for Large Antenna Measurements for Square Aperture With Uniform Field Distribution

Frequency dependences of the field for constant angle of observation measured by different probes at different distances are discussed. We consider the case of the square aperture antenna with the uniform field distribution. The analysis is based on time-domain physical optics method of field calculation. We show and explain the effect of sidelobe reduction when a big square probe is placed at a finite distance from square aperture antenna. Errors of the sidelobe levels of the antenna radiation pattern (ARP) in the cases of different sizes of the probe placed at different distances are shown. We show an optimal probe size and an optimal measurement distance between antennas. We also show and explain the effect of a large distortion of the ARP first zero, measured by the big probe at the finite distance.