User`s guide

RJ + PJ High Pass Filter - A post-processing filter that is applied to the data after acquisition. The filter affects the
determination of what are considered peaks in the FFT views. The highlighted peaks are then reported among the
values displayed in the Summary View. Choices are Natural Rolloff and Brickwall. User can enter value in box
labeled High Pass Frequency (MHz) only when the Brickwall selection is enabled. The displayed values are not used
when options are deselected.
Natural Rolloff – When selected, does not add any filtering but refers to the natural –3db rolloff, or high pass
corner frequency, determined by how much data the tool is allowed to acquire. The corresponding user entry
box is deselected and the value in the box is not used. (see figure below)
Brickwall – is a high pass filter. It does not allow the RJ or PJ to be calculated below this user-selected value. A
user entry box allows entering a frequency value. Any value entered MUST be above the frequency that is set
for the –3db freq. The –3db frequency setting controls how much data is acquired and the Brickwall filter
value is applied to that data. (see figure below)
RJ + PJ Low Pass Filter - A post-processing filter that is applied to the data after acquisition. The filter affects the
determination of what are considered peaks in the FFT views. The highlighted peaks are then reported among the
values displayed in the Summary View. Choices are Nyquist and First Order. User entry is possible in box labeled
Low Pass Frequency (MHz) only when First Order selection is enabled. The displayed values are not used when
options are deselected.
Nyquist – This is the default. The highest
frequency that the tool can measure is ½
the clock rate (or the Nyquist).
First Order – Enter a -3dB frequency. This
filter does not eliminate all the jitter
energy above this frequency (it is not a
brick wall filter). The frequency
components or spectral content above this
frequency will still contribute to the
RJ(RMS) as displayed from the 1-sigma
plot (see figure at right).
RJ + PJ Samples - This is the number of samples
in each histogram. The 1-sigma values used
to create the 1-sigma vs Span plot come from these histograms. See High Frequency Modulation Theory.
RJ + PJ Standard Error - Indicates when suspect measurements have been taken, usually as a result of improper
pattern selection. Default is 0.5 UI. Any measurements deviating from the ideal by more than this value will
produce an error message and the test will stop. This value may need to be increased if the signal has more than
0.5 UI of jitter (such as tolerance testing).
RJ Calculation - This selection determines how the RJ will be calculated in the Known Pattern with Marker tool. There
are essentially three different methods: TailFit, FFT and 1-sigma. Using Tail-fit is the best calculation of RJ, but there
may be trade-offs in test times. For this reason, the special case FFT and 1-Sigma-based RJ calculations are provided.
To determine if you can use the FFT or 1-sigma-based RJ calculation, it is important to look at the graphical results of
the tool. This is especially important in a characterization environment where many different types of jitter or setup
conditions can change which RJ calculation method will provide the most realistic results AND best test times. It is
first important to have a background understanding of how this tool is measuring RJ+PJ. (See the Online Help for
more information.)
Run button/command (Action menu) - Use this command to repetitively acquire new measurements in
GigiView. Measurements will be acquired until either the Single/Stop command is issued or an error
occurs. This command affects the current tool only. Shortcut Key: F5
Sample Size - Number of time measurements included in an Histogram.
Save As command (Tool menu) - Use this command to save and name the active tool. GigiView displays the Save As
dialog box so you can name your tool. To save a tool with its existing name and directory, use the Save command.
Save command (Tool menu) - Use this command to save the active tool to its current name and directory.
When you save a tool for the first time, GigiView displays the Save As dialog box so you can name your
tool. If you want to change the name and directory of an existing tool before you save it, choose the Save
As command. Shortcut Keys: CTRL+S
Glossary © WAVECREST Corporation 2005
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