BNC 645 - Manual (Page 50)

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PM:DEViation {<deviation in degrees>︱MINimum|MAXimum }
PM:SOURce {INTernal|EXTernal}
PM:STATe ON
4.10 FSK Modulation
Model 645 provides the capability to output FSK (Frequency-Shift Keying)
modulation where the frequency of the waveform shifts between two
frequencies (called “carrier frequency” and “hop frequency”). The
shifting rate is determined by the internal or external modulating signal.
Carrier Waveform
The default carrier waveform is sine. One may also choose from square,
ramp and arbitrary waveforms but not pulse, noise and dc waveforms.
The default carrier frequency is 1 kHz for all waveforms. Each carrier
waveform has its own acceptable range of frequencies. Refer to the table
in Section 3.4 “To Set Output Frequency/Period” for details.
Modulating Waveform
Model 645 accepts either internal or external modulating source but not
both at the same time. The default source is internal, and the only choice
is square wave with a 50% duty cycle. When external source is selected,
the carrier waveform is modulated with an external waveform present at
the Trig In connector on the rear panel. The Trig In connector does not
have adjustable edge polarity when used in FSK.
“Hop” Frequency
The default is 100Hz for all functions. Each carrier waveform has its own
acceptable range of allowable hop frequency as follows.
• Sine: 1μHz to 50 MHz(at carrier frequency = 1μHz).
• Square: 1μHz to 25 MHz(at carrier frequency = 1μHz).
• Ramp: 1μHz to 200 kHz(at carrier frequency = 1μHz).
• Arbitrary: 1μHz to 10 MHz(at carrier frequency = 1μHz).
When external source is selected as the source of modulating waveform,
the modulation is controlled by the signal level of the external waveform.