Analog to discrete frequency analysis

Thread Starter


Joined Jun 4, 2011
Say you have the following analog signal given by the equation in the figure and plotted as the green function.

1. You take 48 samples within the 31ms period of the function.
2. You take these samples and upload it to a micro-controller with a Digital to Analog converter.
3. The micro-controller outputs these 48 samples every 10ms. This is shown in the step like version of the green waveform on the oscilloscope capture.

We know the frequency spectrum of the green waveform is are Dirac functions at 31.25Hz and 125Hz.

My Questions:

If we were to design a RC low pass filter to return the Oscilloscope waveform back to the smooth green waveform.

1. Would the oscilloscope waveform have the same frequency spectrum of Dirac at 31.25Hz and 125Hz even though we reduced the period from 31ms to 10ms?

2. How would I analyze the oscilloscope waveform to get the right cut off frequency for my low pass filter?