Millimetre-wave optics and quasi-optical antenna design

The main components of the long-wave optics necessary for quasi-optical system design are listed. The author illustrates their application with reference to a requirement for a radiometer system for Earth-remote sensing from a satellite platform. The system is to operate in three well-separated frequency bands spaced through the millimetre-wave range with a single dual-reflector antenna and a quasi-optical multiplexer to separate the three bands into three receivers. The antenna patterns for the widely-spaced bands are to be very closely matched, with a precisely specified width for the main lobe and with a very high beam efficiency. It is shown how Fourier optics, beam-mode analysis and angular-spectra are all involved in reaching an optical design which meets these demanding requirements