What's all the noise about?

摘要

Manufacturers of signal generators set great store by the specification of phase noise, such that, regardless of the application, phase noise is frequently taken as a proxy of the instrument's overall performance. However, phase noise performance might have little or no impact in some applications. For example, 'close in' phase noise creates problems when the signal generator is being used as a local oscillator, limiting its sensitivity or impairing bit error rate (BER) performance if used as a clock. 'Far out' phase noise, on the other hand, affects wideband communications systems by raising the noise floor and limiting the reception of poor signals.