Tektronix 82A04B, User Manual

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Operating basics
Operation
The operation of the Phase Reference module is based on the acquisition
of a reference clock signal that is synchronous to the signal being
measured. This clock is a user-supplied signal (such as a clock from a
BERT), or the Clock Output of one of the DSA8300 clock recovery or
optical modules. In addition, the user can connect an external trigger
signal to the Direct Trigger input or to the Clock Input/Prescaler Trigger
input of the mainframe.
Phase Ref Free-Run. With no external trigger to the DSA8300 mainframe
needed, the 82A04B module can, together with the mainframe, create
a timebase based on the phase of the reference clock. (Effectively, the
timebase of the instrument functions as a “Phase-base” instead). The
signal displayed on the screen will therefore repeat after one period of
the reference clock. All user controls remain enabled, even while the
horizontal position has relative meaning only. The timing information
presented by the oscilloscope is based solely on the phase reference
clock frequency as entered by the user in the Input Freq
fi eld of the
Phase Ref Setup dialog box. (See page 6, Setup controls .)
Phase Ref Triggered. By providing the phase reference clock to both
the phase reference module and the Clock Input of the instrument, the
DSA8300's Advanced Trigger feature (Option ADVTRIG) can acquire
repetitive pattern data (as opposed to only eye diagrams or clock
signals) with very low jitter.
Characterize. To operate properly in either the Phase Ref Triggered or
the Phase Ref Free-Run modes, the Phase Reference module has to
fi rst Characterize the Phase Reference signal. The signal needs to be
stable during and after the characterization. The instrument indicates
when characterization is necessary.
82A04B User Manual 5