Agilent Technologies 8719D User Manual page 393

Time Domain Operation (Option 010)
With Option 010, the analyzer can transform frequency domain data to the time domain or
time domain data to the frequency domain.
In normal operation, the analyzer measures the characteristics of a test device as a function
of frequency. Using a mathematical technique (the inverse Fourier transform), the analyzer
transforms frequency domain information into the time domain, with time as the horizontal
display axis. 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.
An HP 8719D/20D/22D can be ordered with Option 010, or the option can be
Note
added at a later date using the HP 85019B time domain retrofit kit.
The transform used by the analyzer resembles time domain reflectometry (TDR) measurements
TDR measurements, however, are made by latmching 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.
The Transform Menu
menu consists of the following softkeys:
The analyzer has three frequency-to-time transform modes:
Time domain handpass mode is designed to measure band-limited devices and is the easiest
mode to use. This mode simulates the time domain response of an impulse input.
Time domain low pass step mode simulates the time domain response of a step input. As in
a traditional TDR measurement, the distance to the discontinuity in the test device, and the
type of discontinuity (resistive, capacitive, inductive) can be determined.
Time domain low pass impulse mode simulates the time domain response of an impulse
input (like the bandpass mode). Both low pass modes yield better time domain resolution for
a given frequency span than does the bandpass mode. In addition, when using the low pass
modes, you can determine the type of discontinuity. However, these modes have certain
limitations that are defined in "Time domain low pass," later in this section.