I am checking the Low Pass Filter coefficient to use on my micro-controller,
I have researched some topic, like https://ez.analog.com/message/21166?commentID=21166#comment-21166
I use the excel to verify my formula is correct or not (check with the SigmaStudio compiler window).
I can not get the correct A1 and A2 value but I can get the correct B0, B1 and B2, so I don't know where is wrong.
like this example:
omega(w0): (2 * Pi() * f0 ) / Fs = 0.130899694
alpha( this is from the SigmaStudio Filter Wiki):
alpha = sin(w0) / (2 * Q) = 0.046285884
like below pic:
from the above calculation,
I can get the similar B0/B1/B2:
from mine excel:
but to check the A1 and A2, the value is not correct, I follow the Wiki formula and the reference topic,
so I am not sure which is the correct answer. I don't know my formula is wrong or not.
Here is mine A1 and A2 formula:
A1 = -2 * cos(w0) = -1.982889723
A2 = 1 - alpha = 0.953714116
from the SigmaStudio compiler window A1 and A2 value:
A2 = -0.911523461341858
from the above I can sure is completely different.
Please help me on this.
Thanks you all !