ABSTRACT
This chapter considers noise as a random process. Noise can have many different sources such as thermally generated resistive noise, charge crossing a potential barrier, and generation-recombination noise. The statistics of noise are essential for determining the results of passing noise through nonlinearities because the nonlinearity will change the noise distribution. The noise equivalent bandwidth of a filter is especially useful when measuring noise sources with a spectrum analyzer. Power meters are often used with bandpass filters in noise measurements so that the noise power has a well-defined range. The most accurate and traceable measurement of noise power is by comparison with thermal standards. A transmission line frequency discriminator can provide accurate and high-resolution phase noise measurements without the need for a reference oscillator. Accurate noise measurement and analysis must recognize that noise is a random process.
