33
Modulation
General
The instrument can apply seven types of modulation: AM (Amplitude Modulation), FM (Frequency
Modulation), PM (Phase Modulation), PWM (Pulse Width Modulation), BPSK (Binary Phase Shift
Keying), SUM (Carrier plus Modulating signal) and FSK (Frequency Shift Keying). It is not possible
to apply all modulations to all carrier types or to simultaneously apply more than one modulation to
any carrier type. For example, PWM cannot be applied to sine, and noise cannot be modulated at
all. However, sine and noise may be used as the modulation shape for any type of modulation
except FSK. See the following sections or the Specification section for information on carrier
waveforms and modulation types and shapes which are supported.
Pressing the MOD key will apply the currently selected modulation to the currently selected carrier
waveform and the MOD key will glow yellow. The screen below shows the effect of pressing the
MOD key when Sine is the selected waveform and the selected modulation type is AM.
The Parameters Box now shows the current modulation parameters of
MODFRQ
,
DEPTH
and
SHAPE
and
AM
is shown in the
FCN
field. The Graph Box shows the modulating waveform below
a representation of the modulated carrier waveform. The Edit Box contains the selected parameter, in
this case modulation
Source
.
To change the carrier waveform parameters press the highlighted carrier waveform key which will
return the display to the carrier menu as shown below.
Notice that
AM
still shows in the
FCN
field of the Parameters Box and the MOD key still glows
yellow indicating that modulation is still active. To return to the modulation menu to edit the
modulation parameters press the MOD key again. To turn off modulation press the MOD key while
the modulation menu is displayed.
The following sections discuss the parameter choices for each type of modulation. Only one
modulation type may be applied to any one time.
AM
To select AM press the MOD key to turn on modulation and then press the
Type
soft-key to show
the display below.
