cascaded filter design

Discussion in 'General Electronics Chat' started by vinodquilon, Jun 16, 2010.

  1. vinodquilon

    Thread Starter Member

    Dec 24, 2009
    234
    0
    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 ?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    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.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK, I guess I should have actually read that you are using an RC filter rather than an LC filter. :rolleyes: ;)

    Try simulating your filter in Spice.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    vinodquilon likes this.
  5. vinodquilon

    Thread Starter Member

    Dec 24, 2009
    234
    0
    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.
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    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
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    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.
     
  8. vinodquilon

    Thread Starter Member

    Dec 24, 2009
    234
    0
    Here is my Pulse Amplitude Modulation (PAM) application....
     
  9. Ghar

    Active Member

    Mar 8, 2010
    655
    72
Loading...