Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Comments on Band pass filter given cutoff frequency and bandwidth

Post

Band pass filter given cutoff frequency and bandwidth

+0
−6

I have decided to try design a band-pass filter with a cut-off frequency of 10kHz and bandwidth of 2 Hz.

Image alt text

$$ \frac{1}{\sqrt{LC}} = 10001 \rightarrow LC = 1/100020001 sec^{2}$$

$$ \frac{R}{L} = 2Hz$$$$ \frac{1}{RC} = 2Hz$$

Here is what I have done but if I plug the values to WolphramAlpha

it says it doesnt have any solutions.What am I doing wrong?

History
Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

4 comment threads

What's the purpose? (4 comments)
Unreadable image deleted. (2 comments)
Equations (1 comment)
"Bandwidth"? (1 comment)
What's the purpose?
a concerned citizen‭ wrote almost 2 years ago

Did you mean "center frequency"? If so, even for a 20 dB attenuation at 1000 times the bandwidth in the stopband, I run into numerical issues and can't get such a high order, and thi sis for a Cauer/elliptic filter. You could try a 2nd order, but that would mean a Q of f0/BW=5000. You'll likely need an xtal for that. A 32768 Hz for watches is in the order of tens of thousands. But, before that, can you say what it is for? It sounds like an XY problem.

MissMulan‭ wrote almost 2 years ago

No I don't mean center frequency I mean bandwidth of the pass band filter,the range of frequencies at which the attenuation is higher than - 3dB

a concerned citizen‭ wrote almost 2 years ago

MissMulan‭ I meant about the 10 kHz part because, as Olin says in his answer, that's not a characteristic of a bandpass filter. But you can define it in terms of center frequency and bandwidth (and attenuations in both pass- and stop-band). You haven't answered, though: what purpose will that filter serve? There may be different, less absurd ways to do it -- because a 2 Hz bandwidth at 10 kHz is absurd. For a 2nd order, the settling time will be 4.6 s for 1%.

MissMulan‭ wrote almost 2 years ago

Ya I agree Q will be really high.