User`s guide

Filters - Enables/disables time and range filtering. The Window Filter is a post-processing filter that ignores
measurements acquired outside of the filter parameters. The summary window will show the statistics from the
measurements within the filter window and the histogram view will display the filtered region. The filter does not
change the number of samples that fall within the filtered area, so the Hits Per Edge reflects the total unfiltered
histogram. To increase the number of samples falling in the filtered area, the Hits Per Edge will have to be
increased. For example, if there are two roughly equal distributions displayed without filters and the hits per edge is
set to 1000, the probability of a value occurring in either distribution is equal. Therefore, the filtered data may
contain approximately 500 hits. The window filter can be enabled in any of three ways: 1) choose Max/Min values,
2) choose Center and Width values or 3) From Markers button - Turn filters on, enable markers, place markers at
times on the x-axis to be filtered, press "From Markers". Once filters have been enabled, the reacquired data will
show the filtered region. Maximum and minimum times (+/- 2.49 seconds) can be entered in pico, nano-, micro-,
milli- or seconds depending on Units selection.
Filter Setting - Choose the filter setting. Available filters depend on the options installed in the OE-2™. The installed
filters are read upon instrument power up only those installed will be displayed in this list. Choosing "full
bandwidth" removes any filtering. Different protocols require the use of different filters.
Find Computer... - Displays dialog box that lets the user enter names of computers to find on the network.
Fine Delay - Displays the fine delay setting in multiples of 15.7ps.
Fine Delay Index - Select the number of fine delays, 0-255.
F
max
Divider - Allows scaling of the FFT by dividing the upper frequency end of the FFT. Default is 1, which shows
frequencies of jitter up to 1/2 the clock rate. Changing this value allows faster analysis of lower frequency
information by skipping edges and ignoring high frequency effects. However, changing this value without changing
the -3dB frequency will reduce the number of edges measured.
NOTE: Depending on the frequency of the clock being measured, it is possible that the Nyquist of the clock (1/2 the
clock rate) could intrude into or be below the region chosen as the First Order filter frequency. Additionally, if the
F
max
Divider is set at any value other than one, this will eliminate any frequency content above divided Fmax. For
example, if measuring a 400MHz clock, the Fmax or Nyquist is 200MHz. Therefore, a First Order filter set to
20MHz would be 20dB down at 200MHz. But, if the Fmax divider is set to '2', then the "nyquist" or "Fmax" would
be 100MHz and would cut into the first order filter. In this case, the RJ(RMS) value measured may not contain the
same spectral content as did the measurement with Fmax set to '1'. The reported RJ(RMS) value would be lower
with the Fmax set to '2'.
Force Pulsefind - When on, performs a pulse find after each histogram giving the user updated voltage information with
each run. With Force Pulsefind OFF, the original threshold values are used and do not change.
Force-Fit - Without Force-fit, a Tailfit uses a number of statistics to assess whether the quality of solution is sufficient
before returning a result. Using Force-Fit relaxes these constraints and assumes the user has determined that the
Minimum Hits to perform the Tailfit is sufficient to return valid results.
Frequency (MHz) - Sets the frequency (MHz) or period (ns) of the OUTPUT and OUTPUT signals.
Frequency Resolution (Hz) - Sets the frequency resolution. This determines the number of data points displayed in the
spectrum plot. The minimum number of data points required to generate a plot is 1000. Thus the frequency
resolution must be less than 2000 times the maximum frequency. A small value for the frequency resolution will
increase the measurement time.
From Markers Button - When Filters are ON and the vertical markers are enabled and positioned by the user, clicking
on the From Markers button automatically sets the filters according to the vertical marker positions.
Function (Adjacent Cycle) - Choices are Period(+), to measure between rising edges, or Period(-), to measure between
falling edges.
© WAVECREST Corporation 2005 Glossary
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