BNC 630 - Manual (Page 25)

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5.7 External PM Mode
Introduction
The External PM mode generates a phase modulated signal of fixed amplitude. An externally supplied signal on the Ext Mod In
connector is used to vary the phase of a carrier sinusoid.
External PM Mode Parameters
The External PM mode has the following front panel display:
Figure 5.7-1: External PM mode display
1. Peak Phase Deviation
In this field specify the degree to which the modulating signal is allowed to change the carrier phase. You may enter from 0
degrees (no change) to 180 degrees in 1 degree steps.
This parameter is a peak value. If the deviation value were 180 degrees, for example, then the output phase will advance to a
maximum of +180 degrees and retard to a minimum of -180 degrees for a 1 Vp-p input signal.
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 phase deviation value.
Note: FM modulation is equivalent to PM for small frequency deviation values. If you need a larger phase deviation than 180
degrees, go to FM mode and specify an appropriate peak frequency deviation value.
2. Carrier Frequency
In this field enter the frequency of the carrier. You may enter from 0 Hz (DC) to 21.5000000 MHz in .01 Hz steps.
3. 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 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 voltage turns off the output.
For further information on the Ext Gating Input, refer to section 2.0.
External PM Pk dev: 180 deg
20,000,000.00 MHz -10.0 dBm
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