User`s guide

Histogram Options button - This button will open a menu for configuring a histogram window. The histogram shows
statistics from the samples that fall inside this window.
Hits per Pass - Number of time measurements included in an Histogram.
Hold Time (ns) - Enter the hold time specification. This will change the darkened area on the Data Histogram plot,
showing a window of pass or fail.
Hold Zoom command (Display menu) - Maintain current zoom setting when in Run/Cycle mode.
HPF (kHz) - User defined High Pass Filter value, in kilohertz, for the DCD + ISI HPF option. Default is 637kHz.
HPF -3dB Lower Rolloff Frequency (kHz) - The HPF -3dB Lower Rolloff Frequency is the Frequency of the Half
Power Point of the 20dB/decade low frequency rolloff. The choice of this frequency will determine the low
frequencies visible on the FFT. The -3dB Lower Rolloff Frequency (kHz) is used to determine the maximum
measurement interval to be used in sampling and is entered in kHz. A lower -3dB Lower Rolloff Frequency extends
the time required to acquire the measurement set because histograms over many more periods must be acquired.
Below the -3dB Lower Rolloff Frequency, a natural roll-off of approximately 20dB per decade is observed. The
default value is 637kHz, a Fibre Channel standard, except for the High Frequency Modulation Tool that is 100kHz.
-3dB Lower Rolloff Frequency affects how much data is acquired and, therefore, the choice of this value also affects
the test time. See the Theory Section for High Frequency.
Initial Damping Factor - Either sets or displays the initial guess for fitting of the damping factor, depending on the
setting of the Calc Init Conditions.
Initial Natural Frequency Factor - Either sets or displays the initial guess for fitting of the natural frequency,
depending on the setting of the Calc Init Conditions.
Initial Power Spectral Density Frequency - Either sets or displays the initial guess for fitting of the input noise level,
depending on the setting of the Calc Init Conditions.
Initial Offset Frequency Factor - Sets the lowest frequency displayed when View is set to PLL Transfer.
Input Pairs - Choices are
Differential or Single-Ended. Differential displays the combination of the Input and Input on a
channel. Single-Ended displays the Input and Input signals as independent traces. This is the only mode where the
IN and IN can be treated as independent measurement channels.
Intersymbol Interference (ISI) - Data dependent deterministic jitter caused by the time differences required for the
signal to arrive at the receiver threshold when starting from different places in bit sequences (symbols). For
example when using media that attenuates the peak amplitude of the bit sequence consisting of alternating 0,1,0,1...
more than peak amplitude of the bit sequence consisting of 0,0,0,0,1,1,1,1... the time required to reach the receiver
threshold with the 0,1,0,1... is less than required from the 0,0,0,0,1,1,1,1.... The run length of 4 produces higher
amplitude that takes more time to overcome when changing bit values and therefore produces a time difference
compared to the run length of 1 bit sequence. When different run lengths are mixed in the same transmission the
different bit sequences (symbols) therefore interfere with each other. ISI is expected whenever any bit sequence has
frequency components that are propagated at different rates by the transmission media.
ISI is caused by a data path propagation delay that is a function of the past history of the data. It occurs in all finite
bandwidth data paths. It is also known as Data Dependent Jitter (DDJ).
Interval (s) - Enter time between measurements in seconds. For example, 10 seconds would set the tool to create an
entire histogram every 10 seconds and plot the results. Longer intervals allow long-term tests to be performed
showing measurement changes over minutes or hours.
Invert Pattern - Inverts the selected pattern. This option is useful when using one amplifier on the AG-100.
© WAVECREST Corporation 2005 Glossary
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