Daqarta
Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
Software for Windows
Science with your Sound Card!
The following is from the Daqarta Help system:

# PM Modulation Depth

Macro: PMdepth

This control works differently depending on the modulation type.

With Phase modulation, Depth is the percentage of a cycle traversed by the modulator in each direction. For example, with 50% Depth, the main waveform will slide forward by a half cycle (to +180 degrees) and backward by a half cycle (to -180 degrees). At 100% Depth, it will move a full cycle in each direction.

With Slope modulation of a Ramp wave, Depth is the total slope covered by both positive and negative swings of the modulator. For example, if you set Ramp Rise to 50% and this Slope Depth to 100%, then the modulator will cover the entire range from an equivalent of 0% Rise to 100%.

Note that if you set Depth too large for the Ramp Rise, you can break over into a reversed ramp as the Rise goes below 0 or over 100%. For example, with 25% Rise, you would hit this if you set Depth above 50% (ie, +/- 25%) because you would then go below 0 on the negative modulator peaks.

Similarly, with Pulse Width modulation, Depth is again the total width covered by the modulator. So if you set Pulse A Width to 50% and Pulse B to zero, you will start with a square wave. 100% Depth would then take it from fully off (0% A Width) to fully on (100% A Width) over the course of the modulator cycle. Likewise, you must not set Depth too large for the base pulse widths or the pulse will vanish if the overall width goes to 0, or stay high if it goes to 100%.

Macro Notes:

L.1.PMdepth=50 sets Left Stream 1 PM/Slope/PWM Depth to 50%.

L.1.PMdepth=>1 increments Depth by 1%, while L.1.PMdepth=>-1 decrements by 1%. Only +/-1% steps are accepted.

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