User`s guide

High Frequency Modulation Theory
The High Frequency Modulation Analysis tool enables the user to see jitter accumulation and frequency
components of the jitter. This tool acquires data by creating many histograms of measurements. Each
histogram contains successively increasing numbers of periods. For example, a histogram of single
periods is made, then a histogram of two periods, then three and so forth. By plotting the 1-sigma
values relative to the number of periods, a comparison is made between histograms. When jitter is
present, the 1-sigma values will change periodically. Frequency information can be derived from the
changing 1-sigma values by using a windowed FFT.
Setting the -3dB Lower Rolloff Frequency to the lowest jitter frequency that you are concerned with will
determine the number of histograms that must be made. The Fmax divider allows you to scale the FFT
accordingly.
Section 4 - GigaView © WAVECREST Corporation 2005
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