Measurement Distance Effects on Bayliss Difference Patterns

Abstruct-The effects of measurement distance in distorting low sidelobe difference patterns are examined; this is a sequel to a paper on low sidelobe sum pattern effects. Previous calculations have used obsolete suboptimum aperture distributions. The Bayliss linear distribution is a versatile highly efficient and robust optimum distribution; its use here allows a single curve of sidelobe measurement error versus measurement distance (normalized to far-field distance 2 0 ’ / A ) for a given sidelobe level. Data are given for patterns from a uniform distribution to a 50 dB Bayliss. Difference patterns require slightly larger measurement distances than sum patterns. For example, the first sidelobe of a 40 dB Bayliss pattern is in error 1 dB at a distance of 70’ / A . The results should apply approximately for circular apertures as well.