Multipath Filters (was S/H resonators)

[Grant Richter]

> 
> If you are interested I may try to dig them out and
> to translate the essentials with my clumsy English.
> 
> Anyway, I think this technique may give birth to a whole
> new family of interesting synthesizer filters.
> 

We can only hope!

Please do provide any information you can.
This particular class of filter is very interesting
for a number of reasons. An article in "Speaker Builder" magazine
has a good introduction to "Cepstral" concepts:

http://www.libinst.com/cepst.htm

The article provides a biological justification for evolving
such a brain feature. (hows that for completeness)
A cepsrum is a second order FFT analyzing the "ripples" in 
the first order FFT. It seems to be good for describing the
"features" of comb filters and other filters with repeating
"features".

That I am aware of there are currently three types of device
that produce deliberate comb filters:

Delay lines (peaks with linear spacing)
Phase Shifters (peaks with exponential spacing)
Fixed filter banks (arbitrary spacing)

A fourth type of processor (Theta Processor) was proposed
by Bernie Hutchins in Electronotes and is a delay line
followed by a phase shifter and shifts the comb spacing
in between linear and exponential spacing.
I am basing the linear/exponential spacing thing on the
graphs in the article (which was done on log paper so
everything looks backwards).

These "multipath" filters would form a new type of comb
filter and may be inexpensive to implement or have unique
features.