Agilent Technologies 8719D, User Manual

Page: 406 / 673

Figure 6-72. The Effects of Widowing on the Time Domain of a Short Circuit
In the time domain, range is defined as the length in time that a measurement can be made
without encountering a repetition of the response, A time domain response
repeats at regular intervals because the frequency domain data is taken at discrete frequency
points, rather than continuously over the frequency band.
Measurement range =
where AF is the spacing between frequency data points
Measurement range =
(number of points
1)
frequency
example:
Measurement =
201
points
1
to
2.001
Range or
(number of points
1)
frequency span
1)
(10 (2 x
= 100 x seconds
Electrical length = range
x
the speed of light (3
x
= (100 x x (3 x m/s)
= 30
meters
In this example, the range is 100 ns, or 30 meters electrical length. lb prevent the time domain
responses from overlapping, the test device must be 30 meters or less in electrical length for a
transmission measurement (15 meters for a reflection measurement). The analyzer the
stop time to prevent the display of responses.
Applicationand Operation Concepts