Identifying filter type based on magnitutde reponse

[mngeow]

This question is one on magnitude respone.

Question:

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Answer:

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You can refer to the answer to see the different values you get when you sub in omega,anyway,the rough sketch of the magnitude response from 0 to pi that I got looks like this:

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Looking at the magnitude response it looks like a band stop filter to me,but the answer provided said that it was a low pass filter? Is the answer wrong maybe?Or am I doing something wrong?

Thanks for the help!

 

[SneaKSz]

Chebychev LPF, the reason why the magnitude go's back up because its inherent to the chebychev type, butterworths don't have this.

kind regards

 

[crutschow]

For a band stop filter the right side of the response gain after 2*pi/3 would be as large as the left side. The response at pi is much less then the response at 0 (assuming we are looking at a log or dB plot). This means the response is a low pass filter (with ripple in the stop band).

 

[mngeow]

ooh.No wonder the answers said it was a lowpass filter! Thanks alot. =)

 

[MrAl]

Hi,

Sometimes you have to look at more of the response too. If you look at only part of a response it may look like a bandstop but if you look at more of it you'll see that the hills go up and down several times (looks like a hair comb) but the general tendency is to decrease with frequency so overall it's still a low pass filter.
I havent checked this actual response myself (yet) but from what others are saying that's most likely what threw you off.