What is Noise Floor?

The Noise Floor is the signal created from adding up all the unwanted signals within a measurement system. The noise floor consists of noise from a number of sources which includes thermal noise, atmospheric noise and noise from components used to make the measurement system.

Noise floor is an important parameter in spectrum analyzers and vector network analyzers. It determines the lowest possible signal level that these systems can measure. For example, to measure a signal that is -140 dBm, the system must have a noise floor of less than -140 dBm.

In Spectrum Analyzers and VNA's the Noise Floor is called the Displayed Average Noise Level (DANL).

Noise floor is the sum of all unwanted signals generated within a vector network analyzer (VNA). Noise floor is the minimum input power that the vector network analyzer can measure, since any other signal would be lost in that noise. This noise floor is dependent on the instrument’s specifications, IF bandwidth, averaging and configuration.

Ideally, the VNA should have a low noise floor in order to be able to analyze small currents and voltages. A user cannot see signals that are smaller than the noise floor.