4-9] 



PREDICTION OF TARGET RADAR CHARACTERISTICS 



209 



(a) 

 SNB 0' 



(b) 

 SNB 90° 



01 23456789 10 11 



TRUE NOISE FREQUENCY 

 SPECTRAL ENERGY DISTRIBUTION 



YARDS 

 AMPLITUDE DISTRIBUTION 



Fig. 4-31 Sample Spectra Obtained for the SNB at Target Angles of (a) 0' 

 (b) 90°, (c) 180°, and for (d) the SNB pair. 



a result of theoretical studies, ^^ and measurement programs such as those 

 referred to in Paragraphs 4-7 and 4-8, techniques have been developed with 

 which rather good success can be expected in predicting the radar charac- 

 teristics of a target or target complex if their basic configurations are known. 

 A brief discussion will be given of methods which have been used for 

 aircraft targets. 



Since the dimensions of aircraft are many wavelengths for airborne radar 

 frequencies, the methods of geometrical and physical optics are sufficiently 

 accurate for most purposes. The principal reflections, therefore, come from 

 surfaces which have portions parallel to the wavefront. The aircraft then 

 can be approximated by a small number of bodies of simple shapes, for 

 which the radar lengths can be calculated. Over a small range of angles 

 about any given aspect, the contributions from the mdividual bodies will 

 pass through substantially all values of relative phase, so that the average 



2iSee, for example, Studies in Radar Cross-Sections, XV, University of Michigan, Engi- 

 neering Research Institute, Report 2260-1-T, Appendix A, and further references therein. 



