Fixed point analysis of custom filter realizations

Hey,

I am currently in need of a small realization of a LP-filter and have tried to implement this in matlab in a C-style fashion. I have however problems with the coefficient scaling and are unsure how to do this because of the feedacks involved in IIR filtering.

I have seen that matlab have various tools to support in fixed-point analysis. It is possible to generate a filter object by e.g.

[b,a] = butter(3,0.4); Hd = dfilt.df1(b,a); Hd.Arithmetic = 'fixed'; etc..

In this way I could compare different standard filter structures but I cannot analyze a custom filter. One thing that I would want to do is to start from a Direct-Form-1 filter and then reorganize the operators. That is, I want to move various multiplications and additions and see how this affects the transfer function

Can this be done?

[Honglei Chen]

Hi Joel, I'm not sure if I understand what you mean by "move various multiplications and additions" around. Do you mean, for example, comparing between a direct form 1 and a direction form 2 implementations? Thanks.