Computational techniques for beam waveguide systems

Many of the modern radio telescopes, especially those at millimeter and submillimeter wavelengths, employ beam waveguide (BWG) systems as part of the relay optics. These systems are typically analyzed by using physical optics, Gaussian beams or ray tracing techniques. Physical optics offers high accuracy at the expense of computation time. At the other end of the spectrum is ray tracing approaches that ignore diffraction effects entirely. These methods are fast but sacrifice the ability to predict some effects accurately. This paper describes a methodology for implementing each approach to efficiently calculate the performance of multiple mirror reflector systems. Examples are included to compare the results of each approach and to suggest appropriate conditions under which each should be used.