Low-noise Block Downconverter - Amplification and Noise

Amplification and Noise

The signal received by the LNB is extremely weak and it has to be amplified before downconversion. The low noise amplifier section of the LNB amplifies this weak signal while adding the minimum possible amount of noise to the signal.

The low-noise quality of an LNB is expressed as the noise figure (or sometimes noise temperature). This is the ratio of the amount of noise in the output to the amount in the input, in decibels (dB). The ideal LNB would have a noise figure of 0dB. Every LNB introduces some noise, although clever design, expensive components and even individual tweaking of the LNB after manufacture, can reduce noise levels to very low levels.

Every LNB off the production line has a different noise figure because of manufacturing tolerances. The noise figure quoted in the specifications, is important for determining its suitability, is usually representative of neither that particular LNB nor the performance across the whole frequency range, since the noise figure most often quoted is the typical figure averaged over the production batch.