B&K 4070A - Manual (Page 24)

BK Precision 4070A User Manual Rev.2.2
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5.7 External PM Mode
Introduction
External PM mode generates phase-modulated signal of fixed amplitude were externally supplied signal is used as
a modulating signal to vary phase of the carrier signal. Modulated frequency, level, peak deviation and DC offset
values could be manually entered from the front panel keypad in this mode. External signal gating options is
available in this mode. External PM mode could be entered by pressing “Mode”> “PM” >”2” key at any time.
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 21.5 MHz in 0.01 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
0.1 dBm steps.
NOTE: The level specified is a 50O loaded level. This is the level of the signal, which will appear across a 50O
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 signal. For more information on output offsets refer to section 4.4.
Ext Gating Input
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
1,000,000.00 Hz -10.0 dBm 2
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