Scattering by arbitrary-shaped over-moded waveguides

The first six TE modes were used to compute the RCS (radar cross section) for a shorted trapezoidal waveguide. It was found that the individual-mode RCS patterns did not agree with measured RCS patterns, and it was necessary to use a combination of modes to obtain satisfactory results. The calculated domain single-mode azimuth-plane RCS and measured RCS were compared. This single-mode calculation underestimates the measured RCS. The measured RCS data, taken over a frequency range of 2 to 18 GHz and an angular range of +/-70 degrees , exhibit fluctuations that indicate phase interference between multiple waveguide modes. Since the precise relative phase between the higher order modes are not usually known, a statistical approach was used to compute a mean RCS and standard deviation. A comparison between the statistically calculated RCS and the fluctuating measured data between 6.75 and 6.95 GHz is shown.<>