Basic information about FIR filter

Please tell me:

  1. what is "impule responce"?
  2. what is tap (4 tap filter)?
  3. what do coefficients do in FIR?
  4. what is a "delay" ?
Reply to
faizankhan666
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"impulse", not "impule". In the sampled-time domain an impulse is 1 at sample number 0 and zero everywhere else. An impulse response is what the filter output does in response to an impulse on the input.

The usual way we think about FIR filters is that there's an embedded delay line, so at sample time n we have access to sample n-1, n-2, n-3, and so on, for as many prior samples as we need. Strictly speaking a 'tap' is any point in the delay line where the filter uses the data, but what people usually mean by 'taps' is the number of delays plus one -- so a four tap filter would use sample n, sample n-1, sample n-2 and sample n-3.

They determine the behavior of the filter. If x_n is the signal at sample n and a_m is the m'th coefficient, then your four-tap FIR filter can be expressed as

y_n = a_0 * x_n + a_1 * x_{n-1} + a_2 * x_{n-2} + a_3 * x_{n-3}

See my answer to 2.

One further note: if you're going to do much DSP, you may want to start paying attention to comp.dsp -- this group has good DSP people, but there's more on comp.dsp, and fewer flame wars to distract you.

--
Tim Wescott
Control systems and communications consulting
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Reply to
Tim Wescott

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Regards,

John Popelish
Reply to
John Popelish

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and general googling.

John

Reply to
John Larkin

Thanks....Tim and John...you have given me really helpful information

Reply to
faizankhan666

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