Bnc 645 User Manual download pdf (Page 45)

symmetry), triangle (ramp with 50% symmetry), noise and arbitrary

waveforms. If an arbitrary waveform is chosen, the number of points in

the waveform is limited to 4k points with an automatic decimation

process. The default frequency for internal modulating waveform is 10Hz,

and the acceptable range is from 2 mHz to 20 kHz.

When external source is selected, the carrier waveform is modulated

with an external waveform present at the

Modulation In connector on the

rear panel.

Frequency Deviation

The frequency deviation represents the peak variation in the frequency

of the modulation output based on that of the carrier waveform. The

default value is 100 Hz. Each type of carrier waveform has a different

acceptable range as follows:

•

Sine: 1μHz to 25.05 MHz(at carrier frequency = 25.05 MHz).

•

Square: 1μHz to 12.55 MHz(at carrier frequency = 12.55 MHz).

•

Ramp: 1μHz to 150 kHz(at carrier frequency = 150 kHz).

•

Arbitrary: 1μHz to 5.05 MHz(at carrier frequency = 5.05MHz).

In addition, the maximum allowable value is constrained by the following

two conditions:

•

The frequency deviation must not be greater than the carrier

frequency.

•

The sum of frequency deviation and the carrier frequency must

not be greater than the maximum frequency of the selected

carrier waveform plus 100 kHz; that is, 50.1 MHz for sine,

25.1MHz for square, 300 kHz for ramp, and 10.1 MHz for arbitrary

waveforms.

If a value is set greater than one of the above constraints, Model 645 will

automatically adjust it to the maximum value allowed.

When external source is selected as the source of modulating waveform,

the modulation is controlled by the specified frequency deviation and the

±5v signal levels of the external waveform. When the external waveform

is at +5v, the output will reach positive maximum frequency deviation;

e.g., 100 kHz increase from carrier frequency if the specified frequency

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Bnc 645 User Manual Page 45