Scattering experiments at the Ipswich electromagnetic measurements facility: Calibration with perfectly conducting spheres

A new electromagnetic scattering facility located at Ipswich, Massachusetts is described. A 20 x 20 x 40 ft anechoic chamber was evaluated as to wall reflection coefficient at 10, 35, 98, and 140 GHz. The frequency stability of the measurement equipment was evaluated and was determined not to be a limiting factor in making radar cross section measurements. The backscatter radar cross sections of 24 metal spheres were measured at 10 GHz and compared with theory. The spheres ranged in size from 0.218 to 8.00 inches in diameter, corresponding to a Ka range of 0.581 to 21.293. The measured radar cross sections differed from theory by less than 0.6 dB. Radar cross sections as low as -46 dBsm were measured. The calibrated facility will be used to measure canonical shapes for both metallic and non-metallic targets. The non-metallic results will be used for the Cruise Missile Surveillance Program.