CIC Filter Length
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From: analog_fever on 5 Aug 2010 17:29 I am reading about CIC filters used for an Sigma Delta converter. In that the author mentions that - For a 2nd order filter, decimating by N, the length of the impulse response is 2N+1 - For a 3rd order filter, decimating by N, the length of the impulse response is 3N. - For a 4th order filter, decimating by N, the length of the impulse response is 4N. The filter has to operate for a min number of cycles at least equal to the length of the impulse response. Can somebody explain how he is defining the length of the impulse response here?
From: Rick Lyons on 7 Aug 2010 08:08 On Thu, 05 Aug 2010 16:29:46 -0500, "analog_fever" <usu_vlsi(a)n_o_s_p_a_m.yahoo.com> wrote: >I am reading about CIC filters used for an Sigma Delta converter. In that >the author mentions that > >- For a 2nd order filter, decimating by N, the length of the impulse >response is 2N+1 > >- For a 3rd order filter, decimating by N, the length of the impulse >response is 3N. > >- For a 4th order filter, decimating by N, the length of the impulse >response is 4N. > >The filter has to operate for a min number of cycles at least equal to the >length of the impulse response. > >Can somebody explain how he is defining the length of the impulse response >here? Hello analog_fever, I think the impulse response length of a CIC filter is: Imp. Resp. length = M(N-1) + 1 where M is the order of the filter. You should be able, without too much trouble, to check this using some software. Goos Luck, [-Rick-]
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