Radiation field effects during statistical subreflector surface errors in Cassegrain antennas

Statistical studies and simulation results on gain reduction and sidelobe distortion caused by statistical subreflector surface errors in Cassegrain antennas are addressed. The statistics of the subreflector diffraction pattern which varies with the size of the surface error correlation region is discussed and calculated together with the expectation value of the antenna radiation pattern. The gain reduction is given by the surface error variance using the same relation as for parabolic surface errors. The distribution of the scattered power in the sidelobe region as a function of the surface error correlation region projected onto the parabola leads to an increase of the near-axis sidelobe.