I have designed one LPF using the cut-off frequency equation 1/2*pi*RC.
I am planning to implement the designed filter as a cascaded form of three LPFs.

Then, how can I split-up R & C values into three values each for each section ?

I know, in a cascaded connection net cut-off frequency would be the product of
cut-off frequency of each sections.

So, can I divide net R & C values by 3 to get values of each section ?

 

Have you tried using Elsie?

http://www.tonnesoftware.com/elsie.html

The freeware version will design up to a 7-pole filter.

It's really good for a freeware program. It will save you a lot of time.

 

OK, I guess I should have actually read that you are using an RC filter rather than an LC filter.

Try simulating your filter in Spice.

 

Hello,

Are the filters pure RC filters or are there opamps involved?

Here is a page for filter design:
http://alignment.hep.brandeis.edu/Lab/Filter/Filter.html

It is a link from the EDUCYPEDIA page on filters:
http://www.educypedia.be/electronics/analogfil.htm

You could also take a look at the filterdesign PDF of TI (attached).

Bertus

 

Are the filters pure RC filters or are there opamps involved?


Bertus

All documents here you have presented concentrate on active filters, but here I am dealing with a simple passive RC filter only used for blocking carrier frequency at demodulation stage.

 

Hello,

Can you show us the demodulation stage you have upto now?
If you want to make a passive RC network,
the RC timings off all parts can be the same,
but the impedance of the 2nd should be higher as the 1st
and impedance of the 3rd should be higher as the 2nd.
This is because the followers are loads to the feeding filters.

Bertus

 

If you wish to block a carrier frequency, then I suggest you look at Elsie. Well-designed and tuned LC filters will have far better rejection and lower losses than RC filters.

 

Here is my Pulse Amplitude Modulation (PAM) application....

 

Try this tool:
http://www.national.com/analog/webench#activefilters

Edit:
Errrr just noticed you said passive only. Oh well, it's still an interesting tool.