Fundamentals of a Radio Telescope

In radio astronomy, radio telescopes are used to collect radio waves emanated from cosmic sources. By analyzing these signals, the properties of the sources could be unraveled. A telescope typically consists of the following astronomical instruments: a primary and a secondary reflector, receiver optics which usually includes a lens or a pair of mirrors and a pair of feed horns (one for each orthogonal polarization [or simply a corrugated horn with an orthomode transducer OMT]), waveguides, a mixer circuit, a local oscillator, amplifiers, a detector circuit, and a data processing unit. This chapter provides a concise but complete overview of the working principle of the astronomical instruments involved in the construction of a radio telescope. The underlying physics of the components in a radio telescope, ranging from the antenna to the front-end and back-end systems, are illustrated.