Simulink to see Fourier

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Robert Scott
Robert Scott 2024-4-20
编辑： Pat Gipper 2024-4-22
I have a very simple task but am not being successful.
I have a PWM generator in simulike runing at a certain frequency and certain duty cycle.
I want to take the fourier analysis of it and plot it in a scope.
What i expect to see is the DC component of the perioid signal... (i think?)
So if i have a period signal PWM signal with a magnitude of say 5 and duty cycle of .5 i expect to see a DC of 2.5 out on my scope.
How can i acomplish this? I have tried a few different blocks in simulink but im not getting what im expecting.
Perhaps my expecatations are wrong.

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回答（1 个）

Pat Gipper
Pat Gipper 2024-4-22
I put it in a Matlab Fcn block and it seems to work. See the attached file for details.
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Pat Gipper
Pat Gipper 2024-4-22
编辑：Pat Gipper 2024-4-22
The memory block on the bottom, "io" retains a pointer into the top memory block, "buffer", where the latest sample of the input "u" is stored. "buffer" is a circular memory for storing the block of data for calculating the FFT. I tried to store this information within the Matlab function, but it was extremely unhappy with this attempt. I also wanted to make the FFT length a variable, and this was also problematical. I gave up on this for now and am just using a 32 (or was it 64, I forget?) point fixed length FFT.
You can find memory in the discrete selection of Simulink.
Pat Gipper
Pat Gipper 2024-4-22
编辑：Pat Gipper 2024-4-22
Were you able to open the attached file "fft_fcn.slx"? It was written using Matlab/Simulink 2024a build.

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