User Manual

2)External Source
When modulation source is external, carrier waveform will be modulated by an external
waveform. FM frequency deviation is controlled by ±5V signal level of external modulation
input terminal(Modulation In Connector) on front panel. In positive signal level, FM output
frequency is more than carrier wave frequency, while in negative signal level, FM output
frequency is less than carrier wave frequency. Low external signal level has small deviation.
For example, if the frequency offset is set to 1kHz and the external modulation signal is
+5V, FM output frequency will be the current carrier frequency plus 1kHz. When the
external modulation signal is -5V, FM output frequency will be the current carrier frequency
minus 1kHz.
Modulation wave Frequency Setting
When modulation source is internal, frequency of modulation wave can be modulated.
After enabling FM function, the default of modulation wave frequency is 100Hz. If need to
change, press Param → ModFreq in turn, and the modulation frequency range is 2mHz to
1MHz. When modulation source is external, parameter list will hide the modulation wave
option and modulation frequency option, and carrier waveform will be modulated by an
external waveform. The range of modulation signal input from external is 0Hz to 20Hz.
Frequency Deviation Setting
Frequency deviation represents the difference between frequency of the FM modulated
waveform and the carrier frequency. Settable range of FM frequency deviation is from
1μHz to the maximum of current carrier wave frequency, and the default value is 1kHz.
If need to change, press Param → FreqDev in turn.
Frequency deviation ≤ carrier wave frequency. If frequency deviation value is set higher
than carrier wave frequency, the device will automatically set the offset value to the carrier
frequency’s maximum allowable frequency.
frequency deviation +carrier wave frequency must ≤ the allowed maximal frequency of
current carrier wave. If the frequency deviation value is set to an invalid value, the device
will automatically set the offset value to the carrier frequency’s maximum allowable frequency.
Comprehensive Example:
Make the instrument work in frequency modulation (FM) mode, then set a sine wave with
2kHz from the internal of the instrument as a modulation signal and a square wave with
frequency of 10kHz and amplitude of 100mVpp as a carrier wave signal. Finally, set
frequency deviation to 5kHz. Specific steps are seen as following:
Enable Frequency Modulation (FM) Function
Press Menu → Mod → Type → FM in turn to start the FM function.
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