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From: Vladimir Vassilevsky on 5 Mar 2010 11:45


gretzteam wrote:

> Hi,
> I've been playing with wave lattice filters for a little while and only
> yesterday realized that they were just a structure used to implement the
> same good old transfer function that maps nicely onto the Direct Form I,
> II, transposed etc. For some reason I thought they were a different beast.

It usually helps to read the textbook first.

> Now I wonder how do people come up with new structures. The mapping from
> the transfer function to a lattice wave filter is not obvious at all! Let's
> say that I couldn't just start from DF1 and come up with a lattice
> structure...

Sometimes it could be useful to mimic the topology of analog filters.
BTW, lattice filter originates from analog filter, too.

> Are there still new structures being found yielding power or area
> advantages?

Well, in some cases you can get by lesser numeric precision or avoid
some multiplications in favor of shifts and additions.

> Are there any book or research on this topic?

Any book on filter design has examples of different structures.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
From: glen herrmannsfeldt on 5 Mar 2010 13:45
Tim Wescott <tim(a)seemywebsite.now> wrote:
(snip)

> Sometimes, an effort to circumvent a patent leads to a
> superior solution (I wish I had an example to hand).

Superior or not, the only one I remember is cobalt doped
ferric oxide to circumvent the patent on chromium dioxide.

I do remember having a real BASF cassette with real CrO2,
and that it wasn't as good as the other type II cassettes
that I was using at the time.

-- glen
From: gretzteam on 5 Mar 2010 13:54
>So I don't think there are any techniques out there that are going to
>offer astounding improvements, and techniques that _do_ offer
>improvements are going to do so at the cost of easy understandability.
>Keep in mind that the "direct form" filters have the coefficients of the
>polynomials as gains -- I'm pretty sure that's why they're called
>"direct form". There may be filters out there that are significantly
>'better' in some technical way, but I can pretty much guarantee you that
>you wouldn't be able to look at the code that generates them and just
>write down the filter transfer function.
>
>--
>Tim Wescott
>Control system and signal processing consulting
>www.wescottdesign.com
>

Hi all,
Thanks for the 'philosophical' answers.
Now does anybody know of a group doing active research on finding new
structures?

Thanks
From: Rune Allnor on 5 Mar 2010 14:02
On 5 Mar, 19:54, "gretzteam" <gretzt...(a)yahoo.com> wrote:

> Now does anybody know of a group doing active research on finding new
> structures?

Why would anyone want to? The lattice / ladder structures
date back at least to the '60s / '70s; possibly a lot further.
If there is anything at all going on, it would be in the realm
of Kalman'ish filters, like uncented KFs, H_inf or particle
filters.

This stuff on filter structures is *ancient*.

Rune
From: Tim Wescott on 5 Mar 2010 16:09
Rune Allnor wrote:
> On 5 Mar, 19:54, "gretzteam" <gretzt...(a)yahoo.com> wrote:
>
>> Now does anybody know of a group doing active research on finding new
>> structures?
>
> Why would anyone want to? The lattice / ladder structures
> date back at least to the '60s / '70s; possibly a lot further.
> If there is anything at all going on, it would be in the realm
> of Kalman'ish filters, like uncented KFs, H_inf or particle
> filters.
>
> This stuff on filter structures is *ancient*.

You still see papers in the IEEE Circuits & Systems transactions, mainly
having to do with clever ways to implement them in full-custom silicon.

Perhaps the OP should be asking if there's a good _review_.

A Kalman filter is orthogonal to what (I think) the OP wants -- the
Kalman design methodology finds the best behavioral model of a filter
given some system description and optimization rule; the OP seems to be
looking for different filter topologies to realize a known transfer
function.

For that matter, you could easily want a filter that is both Kalman and
is structured to best use the available numerical precision. In that
case one may want to take a Kalman filter and rearrange it's terms to
better leverage the numeric precision of the processor.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
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