BNC 630 - Manual (Page 20)

15
5.2 Internal AM Mode
Introduction
The Internal AM mode generates an amplitude modulated signal of fixed carrier frequency. An internally-generated sinusoid is
used as a modulating signal to vary the amplitude of a carrier sinusoid. The modulation waveform is not suppressed carrier; i.e. a
fixed amount of carrier power is always present in the modulated signal.
Internal AM Mode Parameters
The Internal AM mode has the following front panel display:
Figure 5.2-1: Internal AM mode display
1. Modulating Frequency
In this field enter the frequency of the modulating sinusoid, from 0 Hz to 10,000 Hz in 1 Hz steps.
2. Percentage modulation
In this field enter the degree to which the modulating signal is allowed to change the carrier amplitude. You may enter from 0%
(no change) to 100% (maximum change) in 1% steps.
To enter a value, type 1 to 3 numeric digits. If you type 3 digits, the value is automatically entered. If you only type 1 or 2 digits,
you can press the MHz key or the KHz key or the Hz key (all are equivalent) to enter the percentage value.
3. Carrier Frequency
In this field enter the frequency of the carrier, from 0 Hz (DC) to 21.5000000 MHz in .01 Hz steps.
4. PEP Level
In this field enter the output level, from 4 mVp-p to 10 Vp-p in 1 mV steps or from -44.0 dBm to +24.0 dBm in .1 dBm steps.
NOTE: The level specified in Internal AM mode is the Peak Envelope Power, or PEP. As a peak-to-peak value, this level represents
the maximum peak-to-peak voltage swing that will result from a 100 percent modulated carrier. If no modulating signal were
applied, the unmodulated carrier would have only half the peak-to-peak swing of a 100% modulated carrier.
NOTE: The level specified is a 50 ohm LOADED level. This is the level of the signal which will appear across a 50 ohm load
connected to the SIG Out connector. Into an open circuit, the output swing will be twice the value entered.
Offset
You can enter an offset voltage for the output waveform. For more information on output offsets refer to section 4.4.
Ext Gating Input
(rear panel connector)
This TTL compatible input can be used to gate the output signal on or off. A logic high level turns off the output.
For further information on the Ext Gating Input, refer to section 2.0.
Int AM: 1,000 Hz Percent Mod: 100%
20,000,000.00 MHz PEP level: -10.0 dBm
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