Basics of Measuring Technique
P. Heymann, Matthias Rudolph · 2021
When measuring the power provided by an RF source, the choice of the indicator depends heavily on the level. This chapter analyzes the RF detection at the diode characteristic and the sensitivity that can be derived from this, since diode measuring heads are also relevant for noise measurement, at least if they are equipped with a pre-amplifier. The simplest way to measure small RF powers is direct rectification at the non-linear characteristic of a Schottky diode. A system of matching element, diode, and following amplifier is called a video detector. Before low noise figures could be realized, it was possible to circumvent the problem by the invention of the Dicke radiometer. The chapter shows the relationship between the noise signal and the inherent noise at the input and the levels available for measurement at the output. This interaction forms the basis for the calibration of the noise measurement receiver.