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Mike Simmonds

AM Modulation on Analog Discovery

Question

Not sure if this the correct forum. Apologies if not.

I want to generate an AM modulated wave with 200% modulation depth.  The WaveForms application appears to allow this.

As shown in the attached file, the results are not what I expected.  I expected to have two equal lobes with the phase of the second lobe reversed from the first.

Are my expectations incorrect or am I setting parameters incorrectly?  Or is there a bug in the Analog Discovery firmware or WaveForms application.

200 percent AM Modulation.jpg

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2 answers to this question

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Hi @Mike Simmonds,

I have moved your thread to where the engineer much more experienced with the WaveForms software will be able to see and respond to your question.

Thanks,
JColvin

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The question was solved in private message.

The preview is correct.
The output will be Carrier * (100% + AM)
With 200% AM index you get output amplitude between 300% and -100%
If you want to be between 2x carrier and zero use 100%AM

Thanks for the explanation.  It encouraged me to look more closely at the effect of offset.
After playing around a bit more, I found that I can get my desired waveform by using 100% modulation and -100% offset.

image.png.3b57fddf13b4c1a2747b27694bb36521.png

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