Radar scattering measurements of cones and computation of transient response

The far zone scattered signal amplitude and phase for two small cone and cone-like targets (sharp and spherically blunted) were measured using a ten-harmonic bistatic radar system. As many as five of the first ten harmonics of 1.085 GHz were transmitted simultaneously. The received vector sum of the harmonics was measured (amplitude and phase) by a network analyzer and stored in a computer. Data were collected as the target moved a half wavelength at the fundamental, and individual data for each harmonic were extracted by Fourier analysis. In either system, empty pedestal (background) data were vectorially subtracted and sphere data were used for system calibration. Data were collected for cones at aspect angles of 0, 10, 20, and 30 degrees for from 0.1 to nearly 4. The behavior of the data is compared to the Rayleigh theory for the lower frequencies and the geometrical theory of diffraction (GTD) for the higher frequencies. These theories do not overlap, and the data allow us to "fill the gap." The data were Fourier transformed to the time domain, and the time response of the targets is discussed.