Agilent Technologies 8510C, Operating And Programming Manual

Page: 274 / 391

11
Introduction to Time Domain Measurements
Introduction
This section pro vides information ab out making reection and transmission measuremen ts
in time domain mo de. Measuremen ts are made in frequency domain are mathematically
transformed in to time domain using the in ternal 8510 computer. The system m ust b e
equipp ed with the 8510 Op erating System Firmw are, Option 010, whic h con tains Time
Domain mo de. Without this option installed, the message FUNCTION NOT IMPLEMENTED is
display ed when
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TIME DOMAIN is selected.
Using Front P anel Controls in Time Domain Mode
In Time Domain mo de, the fron t-panel STIMULUS blo c k k eys 4
ST ART
5, 4
STOP
5, 4
CENTER
5, and
4 SP AN 5 relate to time. They aect the horizontal (time) axis v alue of the display , indep enden t
of the frequency range c hosen. Use the RPG knob, step k eys, or the k eypad for data en try .
The k eypad terminators also refer to time in seconds, using low ercase annotation. As an
example, en tering 4 0.01 5 4 G/n 5 displays 10 picoseconds.
General Theory
The relationship b et w een the F requency Domain resp onse and the Time Domain resp onse in a
net w ork is describ ed with the F ourier T ransform:
F requency Domain ! Time Domain
H(f ) 0 ! h(t)
It is therefore p ossible to measure the resp onse of a device under test (DUT) in the F requency
Domain and then mathematically calculate the in v erse F ourier T ransform of the data to
give the Time Domain resp onse. The 8510C in ternal computer calculates the time domain
resp onse v alue using Chirp-Z F ast F ourier T ransform computation tec hniques. The resulting
measuremen t is the fully error-corrected Time Domain reection or transmission resp onse of
the device, display ed as a real-time v alue. Figure 11-1 sho ws the F requency and Time Domain
reection resp onses of the same device.
Introduction to Time Domain Measurements 11-1