10-2
Time Domain Network Analysis and
Normalization
Normalization, an error-correction process, helps ensure that time
domain network analysis measurements are as accurate as possible. The
HP 54750A Series digitizing oscilloscopes with TDR capability include
normalization as a standard feature. With normalization software built
into the oscilloscope, external controllers and variable edge speed step
generators or risetime converters are not needed. Normalization not
only enhances measurement accuracy, it simplifies the measurement
process.
Time domain network analysis (TDNA), includes both time domain
reflectometry (TDR) and time domain transmission (TDT)
measurements. TDNA measurement accuracies can be improved using
normalization techniques. This chapter discusses normalization and
assumes the reader is familiar with basic TDNA measurements.
Time domain reflectometry (TDR) sends a very fast edge down a
transmission line to a test device and then measures the reflections from
that device. The measured reflections can help to design signal path
interconnects and transmission lines in IC packages, PC board traces,
and coaxial connectors.
Time domain transmission (TDT) measurements are made by passing
an edge through the test device. Parameters typically measured are gain
and propagation delay. Transmission measurements also characterize
crosstalk between traces.
Imperfect connectors, cabling, and even the response of the oscilloscope
itself can introduce errors into TDNA measurements. Understanding
the effects of these errors, and more importantly, how to remove them,
will result in more accurate and useful measurements.
Normalization can be used in TDNA to remove the oscilloscope response,
step aberrations, and cable losses and reflections so that the only
response measured is that of the device under test (DUT). In addition,
normalization can be used to predict how the DUT would respond to an
ideal step of any arbitrary risetime.
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