Directivity of a Spherical Two-Mirror Antenna with an Extended Infrared Receiver

Some characteristics of Cassegrain optical systems, consisting of two spherical mirrors, are considered. Based on simulations in the geometric-optical approximation for a wide range of parameters, we find the relationship between the geometry of an optical system with an extended thermal receiver and the main-lobe width of the angular distribution of the system power. This permits one to optimize the system design on the basis of its performance requirements. We determine the optimal displacement of the small mirror from the quasi-focal area of the large mirror, ensuring the minimum main-lobe width in terms of a given level and a given dissipation factor.