I usually differentiate the two filter realizations as "continuous" or
"discrete" time rather than analog or digital. Common filters implemented
with op amps or LC networks are continuous time filters. IIR and FIR
filters are discrete time implementations. IIR realizations can be directly
translated from continuous time filters using the Z transform. FIR filters
can not as they don't have a translation into continuous time.
The bucket brigade filter implemented with delays and multipliers is a valid
FIR design but is not continuous as it's taking samples of the signal to be
filtered much the same as a DSP would do.
FIR filters do have a constant group delay. IIR filters can be implemented
in many configurations.
Steve KT4FY
----- Original Message -----
From: "Radio WC6W" <wc6w@juno.com>
To: <doug@nc.rr.com>; <amps@contesting.com>
Sent: Wednesday, January 17, 2001 12:16 PM
Subject: [AMPS] DSP & and other curiosities
>
> On Wed, 17 Jan 2001 09:15:46 -0500 "Doug Hall" <doug@nc.rr.com> writes:
> >
> >
> >You have it backwards - FIR filters are phase linear, and have a fixed
> group
> >delay, whereas IIR filters do not. IIR filters mimic the operation of
> analog
> >filters (Butterworth, elliptical, etc.) but FIR filters are not
> realizable
> >in the analog world.
> >73,
> >Doug, K4DSP
> >
>
> Hi Doug,
> Just for the history books, I can offer one example of an "analog" FIR.
>
>
> The Reticon (last I heard acquired by EG&G) FIR filters (part no.
> RT5602, if memory serves this morning) which were implemented with bucket
> brigade technology.
>
> I used one of those to implement an outboard CW filter about 15 years
> ago.
>
> 73,
> Marv WC6W
>
>
>
>
>
>
>
>
>
>
> *
>
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