Re: Alternate approach(s) to introducing FIR and IIR filters

Rune Allnor wrote:
On 21 Jul, 17:53, Greg Berchin <gberc...@xxxxxxxxxxxxxxxxxxx> wrote:
On Jul 21, 11:18 am, Rune Allnor <all...@xxxxxxxxxxxx> wrote:

I have no idea what a "discrete time analog" signal might be.
Does anybody know what this might be?
A continuous-amplitude discrete-time signal? Even that doesn't
describe what I mean.

I did a quick search on "analog transversal filter" and, like you,
found a lot of patents. There looked to be some papers deeper in the
search, though I did not have time to dig very far. But in the good
old days they used to build filters out of analog delay lines. They
were true analog filters -- continuous time and continuous amplitude
-- but they suffered from aliasing just like discrete-time filters.

But they weren't FIRs. Anything where RLC components are parts
can never be FIRs. It's a property of the differential equations
that describe RLC networks.

A while back, someone here on comp.dsp mentioned that SAW filters also
qualify, but I am not terribly familiar with them.

SAWs aren't FIRs, only approximations to linear phase filters.
A different thing. Again, it's a property of the differential
equations.

An ideal SAW device -- one without any edge reflections -- has a finite impulse response response. As the launches wave traverses the chip, pick-up elements receive a signal proportional to their length, analogous to coefficient value. Dual output busses can handle both positive and negative coefficients, but AFIK, it's not don in practice.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
.

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