3- 3
Making Time Domain Measurements
Introduction to Time Domain Measurements
Introduction to Time Domain Measurements
The analyzers with Option 010 allow you to measure the time domain response of a device. Time domain
analysis is useful for isolating a device problem in time or in distance. Time and distance are related by the
velocity factor of your device under test (DUT) which is described in
"Time Domain Bandpass Mode" on
page 3-12.
The analyzer measures the frequency response of your device and uses an inverse Fourier transform (a
mathematical calculation) to convert the frequency domain information into the time domain, with time as
the horizontal display axis. The analyzer's internal computer makes this mathematical calculation using the
chirp-Z Fourier transform technique.
The resulting measurement is the fully error-corrected time domain reflection or transmission response of
the test device, displayed in near real-time. Response values (measured on the vertical axis) now appear
separated in time or distance, providing valuable insight into the behavior of the test device beyond simple
frequency characteristics.
With Option 010, the analyzer can transform frequency domain data to the time domain or time domain data
to the frequency domain.
NOTE The analyzer can be ordered with Option 010, or the option can be added at a later date.
The transform used by the analyzer resembles time domain reflectometry (TDR) measurements. TDR
measurements, however, are made by launching an impulse or step into the test device and observing the
response in time with a receiver similar to an oscilloscope. In contrast, the analyzer makes swept frequency
response measurements, and mathematically transforms the data into a TDR-like display.
Figure 3-1 illustrates the frequency and time domain reflection responses of a test device. The frequency
domain reflection measurement is the composite of all the signals reflected by the discontinuities present in
the test device over the measured frequency range.
Figure 3-1 Device Frequency Domain and Time Domain Reflection Responses
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