Theory of operation
80E04, 80E08/B, and
80E10/B sampling modules
(TDR capable)
The TDR capable electrical sampling modules are low noise samplers, with each
channel capable of generating its own Time Domain Re
fl
ectometry (TDR) step.
For these modules, a single strobe, delivered from the instrument mainframe
to both acquisition channels, controls the timing of the strobe assertion to both
channels. If channel-to-channel deskew is zero and the channel delays (if
equipped) are matched, the sampling coincidence between channels is very close.
Acquisition deskew function is accomplished by making separate acquisitions
over acquisition windows or by adjusting Channel Delay (if equipped).
Each electrical channel features a Tekprobe Level 2 probe power connector for
attachment of a real time probe. The control of this probe is a mainframe function.
All module calibration signals are derived from a 2.5 V precision voltage reference
internal to the sampling module. Settings derived from this reference are stored in
a nonvolatile EEPROM in the sampling module, although the responsibility for
the execution of these settings is with the mainframe.
When used in the acquisition mode (that is, with the TDR step generator turned
off) each channel functions as a normal sampling input. In the TDR mode, a
fast rise time step is generated internally for each channel and applied to the
input signal path for that channel. The acquisition part of the TDR/sampling
module remains functional for monitoring the primary step and its re
fl
ected
components. The sampling module provides two self-contained TDR channels.
You can select the polarity of the output step independently for each channel. This
allows differential or common mode testing of two coupled lines and independent
testing of isolated lines.
Optical sampling modules
The optical modules share the same mechanical package and are built with similar
circuit boards. Different functionality within the modules (current and future
modules) is achieved by installing different O/E modules,
fi
lters and clock
recovery boards along with setting the sampler bandwidth. The optical module
key features are:
A one channel, low noise, adjustable bandwidth sampler allowing multiple
bandwidth settings for optimizing noise versus bandwidth demands.
An ampli
fi
ed or nonampli
fi
ed O/E converter.
Support for internal RF switches in the signal path with a straight-through
path and three hardware-
fi
ltered reference receiver paths between the O/E
converter and the sampler.
An averaging optical power meter.
DSA8300 Digital Serial Analyzer and Modules Service Manual
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