Optical approximations for simulations of submillimeter systems

Propagation aspects of systems working in millimeter and submillimeter bands can be solved by quasioptical approaches including Gaussian beams. Reflections from rough surfaces nevertheless introduces complex problem. It can be very well solved by an approximation using methods from free space optics with incorporation of particular corrections of the pure optical approaches. The paper discusses the advantages and drawback of these simulation approaches, based on measurement and analyses of electromagnetic wave propagation.