Stanford Research Systems DS345, Manual

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Modulation and Sweeps
2-17
PHASE MODULATION
Introduction
The DS345 is capable of phase modulating any of its output functions, ex-
cept NOISE and ARB, using its internal modulation generator. The modula-
tion waveform may be a sine, square (PSK), triangle, ramp, or arbitrary pat-
tern (see ARBITRARY MODULATION section for information about ARB
patterns). The rear-panel MODULATION OUTPUT outputs a signal with 0V
corresponding to the largest negative phase deviation and +5V correspond-
ing to the largest positive phase deviation.
Phase Span
During PM the DS345 outputs a signal whose frequency is centered about
the programmed frequency. SPAN sets the amount that the phase varies rel-
ative to zero phase. The minimum phase shift output will be -SPAN/2, while
the maximum phase shift output will be +SPAN/2. The value SPAN/2 is com-
monly called the
deviation
(that is, SPAN = Deviation x 2). The SPAN is dis-
played and set by pressing [SPAN]. The value of the SPAN may be set with
0.001° resolution with a range of 0° to 7199.999°.
Modulation Rate
Press [RATE] to display and set the frequency of the modulating function.
The frequency may be set with two digits of resolution in the 0.001 Hz to 10
kHz range.