- #1
Bassalisk
- 947
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So I am playing this game.
Guess the signal from its amplitude spectrum(FFT). Signal is periodic. I am currently playing with square wave and what are its characteristics. I am using MATLAB function square to do this.
I set the sampling to 500 Hz.
So above 250 Hz I get aliasing.
So far I got this:
When I use frequencies that are well below 250Hz, 150Hz for example, I get a clear delta in amplitude spectrum at 150 Hz.
http://pokit.org/get/c9a4f5cd7e2b0fc3d461c113f8c2e833.jpg
Another example is for 100 Hz
http://pokit.org/get/821f8411db350e1ac31c2ec168251b68.jpg
I concluded that at even Frequencies I get a delta in 0.(even frequencies like 100 120 Hz etc). Why is that?
And for frequencies between like 100Hz 150Hz I get all these little harmonics, like so:
http://pokit.org/get/e3ca4d9d81017657a4965ce5db9577d1.jpg
Can anybody explain this to me? Why do I get these small harmonics? This is closely related to the sampling which is at 500 Hz, and most weird case of all:
At 240 Hz:
http://pokit.org/get/a49e3210ca2067d5b7a20ce61038d659.jpg
I am completely baffled with these small harmonics!
Can any signal wizard, relate these small harmonics with sampling rate?
Thanks
Guess the signal from its amplitude spectrum(FFT). Signal is periodic. I am currently playing with square wave and what are its characteristics. I am using MATLAB function square to do this.
I set the sampling to 500 Hz.
So above 250 Hz I get aliasing.
So far I got this:
When I use frequencies that are well below 250Hz, 150Hz for example, I get a clear delta in amplitude spectrum at 150 Hz.
http://pokit.org/get/c9a4f5cd7e2b0fc3d461c113f8c2e833.jpg
Another example is for 100 Hz
http://pokit.org/get/821f8411db350e1ac31c2ec168251b68.jpg
I concluded that at even Frequencies I get a delta in 0.(even frequencies like 100 120 Hz etc). Why is that?
And for frequencies between like 100Hz 150Hz I get all these little harmonics, like so:
http://pokit.org/get/e3ca4d9d81017657a4965ce5db9577d1.jpg
Can anybody explain this to me? Why do I get these small harmonics? This is closely related to the sampling which is at 500 Hz, and most weird case of all:
At 240 Hz:
http://pokit.org/get/a49e3210ca2067d5b7a20ce61038d659.jpg
I am completely baffled with these small harmonics!
Can any signal wizard, relate these small harmonics with sampling rate?
Thanks
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