DIGITAL MODULATION MODE
3-30
Test tones utility
The test tones facility allows verification of the instrument performance by internally generating
two audio sources with independent level and phase adjustment and a DC offset control. The
facility can also be used for generating SSB signals.
Selecting Test Tones from the
Digital Modulation Type Selection
menu (Fig. 3-22), causes the
Digital Modulation System Menu
to be displayed as shown in Fig. 3-27.
Q DC
Offset
IQ
Angle
I
Ampli.
Q
Ampli.
I DC
Offset
Tone
Freq.
LOCAL
Select
System
Select
Mod Type
Digital Modulation System Menu
Test Tones Utility
Tone Frequency: 10.000 kHz
I Amplitude
:
500 mV pk
I DC Offset
:
0 mV
Q Amplitude
:
500 mV pk
Q DC Offset
:
0 mV
IQ Angle
:
90.0
°
C1630
Fig. 3-27 Digital modulation: Modulation system menu with test tones selected
Test tones operation
With
[IQ O/P Enable]
selected from the
Digital Modulation Configuration
menu (see Fig. 3-40
below), the test tones generated at the I and Q IN/OUT sockets are sine waves at a selected
frequency and phase angle. If the test tones are set to generate equal amplitude signals separated
by 90
°
or 270
°
the RF output will be an SSB signal. Adjusting the DC offset will introduce carrier
leak. The I and Q amplitudes and DC offsets can be individually set as follows:
To set the test tone frequency press
[Tone Freq.]
and enter a frequency up to 29 kHz to a
resolution of 1 Hz.
To set the IQ angle, press
[IQ Angle]
and enter an angle in the range 0
°
to 360
°
to a resolution of
0.1
°
.
To set the I or Q amplitude, press either
[I Ampli.]
or
[Q Ampli.]
respectively and enter a voltage
to a maximum of 1.6 V and a resolution of 1 mV.
To set the I or Q DC offset, press either
[I DC Offset]
or
[Q DC Offset]
respectively and enter a
voltage to a maximum of 1.6 V and a resolution of 1 mV.
Menu exit
Press
[Select System]
or
[Select Mod Type]
to return to the respective menus. Press [SIG GEN] to
return to the
Sig Gen
menu where further selections may be made.