AN10072 Determine the Dominant Source of Phase Noise, by Inspection

This application note presents a novel three-step procedure to determine, by inspection, the location in a phase noise curve that dominates its integral. This location contributes more to an integrated phase noise result than elsewhere in the curve. The procedure can be used to help understand the dominant source(s) of noise present in a signal, as well as simplify the integration process by reducing the amount of data to analyze. A mathematical basis for the procedure is provided, which extends its application beyond phase noise to include logarithmic plots of other quantities for power (e.g. dBm) and fields (e.g. nV/√Hz). Refer to application note AN10062 Phase Noise Measurement Guide for Oscillators for a theoretical overview of phase noise and methods and recommendations of phase noise measurement.

Read this application note to learn how to apply this three-step procedure, how to account for the bandwidth that "views" only a portion of the phase noise plot, how to factor for spurious noise, and how to better understand sources of noise.

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