Distorted Reflector Antennas: Analysis of Radiation Pattern and Polarization Performance

Surface distortions change the radiation characteristics of reflector antennas. Using functional calculus, radiation integral is analyzed, and the first variational derivative (VD) of the radiation field with respect to surface profile is extracted. The VD can show the radiation pattern sensitivity to surface distortion. All formulations are based on the physical optics approximation. The final formula for VD depends only on the original undistorted antenna parameters, so it can be used for all types of distortions. It has been shown that the formulations are more general than those in previous works. Different polarization states of feed antenna are studied, and VD amplitudes are plotted to depict the regions that have greater effects on the main-lobe and the first few side-lobes levels. Some periodic, aperiodic, and local distortion profiles are considered, and the exact and approximated distorted patterns are compared to check the accuracy of the presented procedure.