How do I know how the output of FIR filter were calculated (e.g., each of summands of the FIR)?

For a given set of FIR coefficient b and input data input, I generate FIR output using filter function (e.g., output = filter(b, 1, input)).

Based on the help explaination, the filter is a "Direct Form II Transposed" implementation of the standard difference equation:

a(1)*y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb)

- a(2)*y(n-1) - ... - a(na+1)*y(n-na)

Is there a way to know each of summands before the summations, i.e., b(1)*x(n), b(2)*x(n-1), ..., for each of input or time instance?

[Paul]

Hi Jay,

Based on filter, the terms b(2)*x(n-1), ... don't appear in its implementation. Is the goal to compute intermediate terms in the filter() implementation?

[Jay]

Hi Paul,

Thanks for the comment. I want to know the intermediate terms for verifying hardware implementation. Is there any way or fuction to provide the intermediate terms? Otherwise, it seems that I need to model it.

[Paul]

AFAIK, there is no function that provides the intermediate terms from filter. The actual implementation of the filter is shown in the More About section of the doc page from which one could, in principal, compute the intermediate terms, by which I mean the w_i.

Maybe there is an alternative function to filter() that will do the filtering and provide additional outputs of intermediate quantities.

[Jay]

Thanks Paul. Perhaps I need to model and implement a FIR to populate the intermediate terms. Thanks!