Diffraction pattern by a trapezoidal cylindrical cavity

Asymmetric diffraction patterns for a trapezoidal cylindrical cavity are calculated for the case in which the cavity size is comparable with the wavelength of the incident field. It is shown that asymmetric double dips and null patterns in the near-field region are also present. Amplitude and phase variations of the scattered field are calculated to show how they generate these double dips and null patterns as a function of frequency. The asymmetry of the cross section yields two different null frequencies, corresponding to the upper and the lower boundaries, respectively.<>