62
Chapter 2
Making Measurements
Example 3: Modulation
The following equation also determines percentage of modulation using
amplitude units in volts:
Frequency Modulation
This section contains general information about frequency modulation,
as well as a procedure for calculating FM deviation using a spectrum
analyzer.
For sinusoidal modulation where either the modulation frequency or
the FM deviation can be varied, the spectrum analyzer can be used to
accurately set up a modulation index corresponding to a Bessel null.
The following example illustrates how to verify the FM deviation
accuracy of a signal generator with FM capability. We will use a carrier
frequency of 100 MHz and test for FM deviation accuracy at a 25 kHz
rate using the modulation index for the first carrier null (2.401). Figure
2-9 illustrates how to set up the equipment for this measurement.
Figure 2-9
FM Deviation Test Setup
1. Connect the signal source to the spectrum analyzer INPUT 50
Ω
. Set
the source to 100 MHz.
2. Press
PRESET
to begin with the spectrum analyzer in a preset state
and change the settings as follows:
a. Set center frequency to 100 MHz.
b. Set span to 100 kHz.
c. Set resolution bandwidth to 1 kHz.
d. Set video bandwidth to 1 kHz.
where A
s
= sideband amplitude, in volts
A
c
= carrier amplitude, in volts
M
2 A
s
100
×
A
c
------------------------
=
Summary of Contents for 8560E
Page 21: ...21 1 Quick Start Guide ...
Page 48: ...48 Chapter1 Quick Start Guide Manuals Available Separately ...
Page 49: ...49 2 Making Measurements ...
Page 164: ...164 Chapter2 Making Measurements Example 13 Making Pulsed RF Measurements ...
Page 165: ...165 3 Softkey Menus ...
Page 182: ...182 Chapter3 Softkey Menus Menu Trees ...
Page 183: ...183 4 Key Function Descriptions ...
Page 228: ...228 Chapter4 Key Function Descriptions Key Descriptions Figure 4 3 CRT Alignment Pattern ...
Page 289: ...289 5 Programming ...
Page 323: ...Chapter 5 323 Programming Math Functions Figure 5 10 Display Units ...
Page 339: ...339 6 Programming Command Cross Reference ...
Page 369: ...369 7 Language Reference ...
Page 654: ...654 Chapter7 Language Reference VTL Video Trigger Level ...
Page 655: ...655 8 Options and Accessories ...
Page 665: ...665 9 If You Have a Problem ...
Page 674: ...674 Chapter9 If You Have a Problem Power Requirements Figure 9 2 AC Power Cables Available ...