Axial Cross Polarization in Reflector Antennas with Surface Errors of Large Correlation Diameter

Equations for boresight cross polarization and isolation of axisymmetric and offset antennas in the presence of surface errors are derived in terms of numerically computable integrals. Computations revealed that 1) for root mean square (rms) error <λ/4 cross polarization increases monotonically with increasing rms error; and 2) maximum cross polarization occurs when the correlation diameter is 0.5 D for axisymmetric antennas (0.8 D for offset antennas). For rms error >λ/4 boresight cross polarization remains almost constant. Furthermore, results revealed that for given correlation diameter and rms error, axisymmetric antennas offer better boresight isolation in comparison with offset antennas having the same polarization efficiency.