White PaperTest & Measurement

Understanding Phase Noise Fundamentals


A stable frequency source is a common requirement for many electronic and most RF devices. Phase noise is the term used to describe measurements of the short-term frequency stability of these sources.

Phase noise is the term used to describe short term variations in phase or frequency stability, with “short term” referring to time intervals on the order of seconds or less. Another way of defining or describing phase noise is as random or unintentional phase modulation. Short term stability or "good phase noise performance" is very important in a wide variety of RF applications, but this short-term stability can be difficult to obtain, with a substantial cost and complexity often associated with even modest increases in phase noise performance.

The importance of minimizing phase noise can best be understood by looking at the effects of excessive phase noise. The three most common effects of phase noise are spectral regrowth, decreased sensitivity/selectivity, and increased bit errors.

This white paper provides a brief technical introduction to phase noise concepts as well as an overview of how phase noise is measured and reported.

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