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In the past few years, the development of In-based devices has enabled receiver systems with record noise temperatures and low power consumption. Incoming Sb-based devices promise to achieve their lowest noise at even lower power consumption. Both technologies, although not yet mature, are usually adequate for designers working with very low noise requirements and very low power consumption. Nevertheless, for some applications, these requirements are critical and a specific technology has to be applied to fulfill such conditions.

In radioastronomy, the lowest noise of the receiver system is always the cornerstone around which that system is designed, since the required integration time to reach a certain signal-to-noise ratio is proportional to the square of the receiver noise. Usually, the system noise requirements are below 20 K of equivalent noise temperature, T_e, which can only be achieved if the receiver is cooled down to cryogenic temperatures.^1,2

In order to design and test the different systems, the microwave engineers working in radioastronomy applications have to design and set-up a cryogenic facility in which to carry out reliable measurements. Therefore, these engineers have to gain knowledge in cryogenic related issues, which are far out of their professional training.