Single pole filter, difference equation and documentation

Hi,

I notice from the documentation that all of the different
single_pole_* filters have the same difference equation. Is this
correct?


Trond D.

On Fri, May 11, 2007 at 01:01:44PM +0200, Trond D. wrote:

Hi,

I notice from the documentation that all of the different
single_pole_* filters have the same difference equation. Is this
correct?


Trond D.

I was wondering that myself the other day :wink:

I haven’t had the time to check them out yet.

Eric

gr_single_pole_avg filter kernel:

output = d_alpha * input - d_one_minus_alpha * d_prev_input;
d_prev_input = input;

gr_single_zero_avg filter kernel:

output = d_alpha * input + d_one_minus_alpha * d_prev_input;
d_prev_input = input;

gr_single_pole_iir filter kernel:

output = d_alpha * input + d_one_minus_alpha * d_prev_output;
d_prev_output = output;

gr_single_pol_rec filter kernel:

output = d_alpha * input + d_one_minus_alpha * d_prev_output;
d_prev_output = output;

So it looks like the first three blocks compute different things but the
fourth is a duplicate of the third. The difference equation in the
header files is the same for all four, but is only correct for the last
two.


Johnathan C.
Corgan Enterprises LLC
http://corganenterprises.com

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