10th order filter

Discussion in 'The Projects Forum' started by Ric Pompey, Jul 25, 2012.

  1. Ric Pompey

    Thread Starter New Member

    Mar 8, 2012
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    Hello. I have a project that i have to design that entails using a selector switch to select one of eight different frequencies between 2970HZ and 4950HZ. These frequencies, when selected, must pass through a 10th order filters.
    My question is can someone recommend an IC ( chip) that will reduce my parts count and allow me to achieve 10th order filtration when one of the eight frequencies is selected.

    Thank you,
    Ric Pompey
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Is the filter HP, LP, or BP?
     
  3. Ric Pompey

    Thread Starter New Member

    Mar 8, 2012
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    It has to be a highly selective filter so that when one of the eight freqencies is selected via some kind of selector switch or dial only that freqency will pass through. The requirement for my application is that the filtration must be 10th order. It is posible that a may need eight different 10th order filters each one configured to pass one of the eight different frequencies.
     
  4. ramancini8

    Member

    Jul 18, 2012
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    A 10th order filter is almost impossible to make with discrete parts, and it will not be tunable. I suggest that you square up the waveform and drive it into a DSP where 10th order adjustable filters are an every day project.
     
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  5. crutschow

    Expert

    Mar 14, 2008
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    Why do you need a 10th order filter?
    What is the separation between frequencies?
    Are they all the same amplitude?
     
  6. Ric Pompey

    Thread Starter New Member

    Mar 8, 2012
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    I work in the train control industry. In this industry, train detection is achieved along the rail using track ckts. These track ckts. Consist of the modulation of eight different audio frequencies and are rotated in such a way that no frequency that is the same will be adjacent ( this is how frequency separation is achieved as they are modulated onto the track). This transmitted signal is is sent onto tracks to impedance bonds that block 750vdc used for traction power but pass the frequency of that particular track ckt. At the other end of the impedance bond, there is another bond that passes the frequency in question to a rcvr which filters and demodulates the signal. The filtration within these rcvrs has to be 10th order for safety consideration.
     
  7. bertus

    Administrator

    Apr 5, 2008
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  8. crutschow

    Expert

    Mar 14, 2008
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    If you really need a 10th order bandpass function (which seems overkill to me) then that would require a large amount of analog circuitry (7 to 10 op amps per frequency -- see the free FilterPro software from Texas Instruments).

    It may be preferable to go with digital filters using an A/D converter to convert the signal to digital format and a Digital Signal Processor (DSP) to perform the filter function. Generation of the program for that requires a fair amount of DSP programming expertise, of course.
     
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  9. SgtWookie

    Expert

    Jul 17, 2007
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    Just saying "I need a 10th order filter" is really quite vague.
    You say you need a bandpass filter, but not how wide the filter must be (passband), nor the stopband frequency and depth, is group delay important, how much ripple in the passband is allowed, nor what generic type of filter.
     
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  10. Ric Pompey

    Thread Starter New Member

    Mar 8, 2012
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    Yes, it does sound like over kill, however, it is the transportation industry. We move people. It is an enviornment where the words fail safe and redundancy checks rule. Thank you for your tips.
     
  11. crutschow

    Expert

    Mar 14, 2008
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    Do you have any performance requirements other than it should be a 10th order filter (since that is a design requirement, not a performance requirement)?
     
    Last edited: Jul 31, 2012
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