Effect of field amplitude taper on measured antenna gain and sidelobes

One of the criteria for the quality of the field in which the test antenna is immersed is amplitude taper over the field. Amplitude taper of the field of a pattern measurement range produces gain and sidelobe values lower than the true values. A calculation is presented which uses one-parameter distributions, for which the gain can be found in closed form. It is found that for small tapers, both gain errors and sidelobe level are linearly proportional to taper. Results are useful in the design of pattern ranges, especially for very low sidelobe antennas, where the amplitude tapers are more critical.