Re: Some questions on digital filter design

#364

Mr.?Marks,

Your?post??is?completely?off?topic?relative?to?my?initial?post?about?the?glaring?cognitive?dissonance?inherent?in?the?EE?community?practice?of?substituting?non-causal?digital?filters??for?causal?analog?filters.

I?shall only??note?the?following?quotation,

?"...?the?refractive?index?for?refraction?from?vacuum?into?that?medium.

n=v/C"

Born?and?Wolf?p.?13?of?the?7th?edition?of?"Principles?of?Optics".

That?value?can?NEVER?be?negative.?A?negative?result??indicates?a?major?cognitive?blunder.

The?entire?post?is?a?exercise?in??"baffle?them?with?bullshit"?and?not?worthy?of?further?comment.?I?should?much?appreciate?it?if?you?would?refrain?from?such?practice.

There?is?an?aphorism,?"The?best?response?to?a?fool?is?silence."?I?have?a?well?deserved?reputation?of?ignoring?that?and?not?suffering?fools?quietly.?I?have?long?said?when?asked?where?I?got?my?doctorate,?"I?didn't?and?be?very?wary?of?someone?who?advertises?the?fact."? I?suggest?you?bear?that?in?mind.

Have?Fun!
Reg

Show quoted text

On?Saturday,?July?6,?2024?at?02:07:58?PM?CDT,?Daniel?Marks?<profdc9@...>?wrote:

A?lot?of?papers?have?been?written?and?ink?spilled?over?misapprehension?as?to?what?group?delay?means.?Lots?of?press?about?"signals?arriving?before?they?were?sent."?They'll?say?anything?these?days?to?get?you?to?click.

It?does?not?imply?some?magic?suspension?of?causality.?Negative?group?delay?only?occurs?for?very?small?bandwidths,?such?that?the?impulse?response?width?is?longer?in?time?than?the?negative?group?delay.?Certainly?interesting?phenomena?happen?in?these?narrow?bandwidth?regions?(for?example?a?negative?index?of?refraction)?but?these?are?only?time?harmonic?responses?which?take?a?sufficient?amount?of?time?to?set?up.

But?I?think?this?digression?into?causality?misses?the?point?when?discussing?communication.?The?time-domain?signals?corresponding?to?the?symbols?span?a?linear?subspace?and?have?distances?apart?(for?example?Euclidean?or?Hamming?distances).?Of?course?these?signals?must?be?causal.?A?pure?sinusoidal?waveform?is?not?causal.?So?if?one?is?using?a?filter?bank?to?separate?frequencies,?one?has?to?decide?how?to?handle?finite-time?sinusoids?(for?example?Gaussian?envelopes?or?cyclic?prefixes).

Because?the?signal?processing?computation?can?be?a?limiting?factor?in?real-time?processing,?this?basis?is?sometimes?partially?determine?by?the?signals?that?can?be?more?readily?processed.?For?example,?FFT?/?OFDM?is?an?example?of?exploiting?symmetry?in?the?filters.?Of?course,?with?a?filter?bank?with?only?a?few?frequencies,?it?might?make?more?sense?to?use?a?small?number?of?FIR?or?IIR?filters.

There's?a?lot?that?is?determined?by?the?specifics?of?what?the?goals?are?and?what?the?available?computational?resources?are.?A?modern?PC?has?an?enormous?amount?of?processing?power?to?be?used?on?a?2.5?kHz?wide?SSB?signal.?Some?examples?of?QRSS?using?very?long?convolutional?codes?have?been?able?to?nearly?approach?the?limit?of?-1.59?dB?Eb/N0.

Dan

Re: Some questions on digital filter design

#363

Mike,

In particular I was referring to the reflection seismology community. I find it very grating that the EE community doesn't properly credit Wiener and his "yellow peril". Big oil was the only significant source of DSP research funding before the late '60s. No one else with enough money to pay the bills could do anything within the limitation of a 250 Sa/s sample rate.

I wish I could have worked as long as you did. I "retired" from Houston to Arkansas to look after Mom and Dad in 2007 fully expecting I'd simply shift to working remotely most of the time with a full week in Houston once a month. 2008 killed that and left me devastated by the loss of my social contacts. I never wanted to retire. Just drop back to 3-6 months a year.

I'm still not relicensed after letting my novice ticket lapse in 1987. But I've been actively working on my CW skills and will only be using CW in some form once I take the exams. Like Dad I'm pure radio nerd rather than a ham.

Have Fun!
Reg

On Sunday, July 7, 2024 at 07:42:05 AM CDT, Mike Feher <n4fs@...> wrote:

Nice reply, Reg, thanks. I was just wondering since you were talking about all sorts of processing that you said “we” were doing back in the 50’s and the 60’s. So, by “we” you meant people/industry in general. Looking back, my actual DSP work started in the late 60’s and continued till I retired in 2016. My last 30 years were more in the advisory mode than actual design. I still think the Weaver approach would be the best for your tunable filter.? Believe Rabiner & Gold had a comprehensive article in the IEEE way before their book came out. Referred to it often. Also when the Remez exchange algorithm resurfaced was a game changer. I remember when QEX started. Paul Rinaldo lived the next town over from me, when I lived in VA. He asked me to do a paper on digital filters. I did and he said it was too math heavy and asked me instead to present the main principles to a local radio club. I did, and most were rolling their eyes or were just plain bored. That totally turned me off to the idea of QEX. Best wishes with your quest. 73 – Mike

?

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Reginald Beardsley via groups.io
Sent: Sunday, July 7, 2024 8:03 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design

?

LoL :-)

No, Mike, I'm only 71. I have a large library and a lifelong habit of reading the original papers and monographs, e.g. Shannon, Weiner et al. I've discovered quite a few citations which were incorrect. My BA is in English lit and my MS in igneous petrology. In those days I could read 600-800 wpm.

In January 1982 I accepted an offer from Amoco to take up geophysics with the promise of extensive training in Tulsa. I had so much fun taking Calculus I that I took II, III and Differential Equations. Very rare for a geologist to learn mathematics at that level. It's changed a bit since, but it was still a primarily descriptive discipline then.

That was actually my only option as the mining sector was in such a deep slump that all the North American mines were closed except for Sudburry complex. In April I received a letter informing me that my offer was rescinded if I didn't report for work on 21 May. I defended on a typescript, drove to New Orleans and locked my keys in the car in front of the Hyatt next to the Amoco offices.

Upon reporting for work the next morning I was informed that my formal training was delayed indefinitely and given a pile of Western field tapes from the late '60s which I was to reprocess through to final migration, the operation that collapses the diffraction hyperbolae of point diffractors to a point. I was provided 2 books. "Reflection Seismology" by Waters, 2nd ed and "Seismic Exploration Fundamentals" by Coffeen. I bought a copy of "Geophysical Data Analysis" by Robinson and Treitel and borrowed a copy of "Time Sequence Analysis in Geophysics" by Kanassewich from the company library. Evenings and weekends I used them to teach myself the rudiments, assisted greatly by my first boss who was an EE and had worked as a programmer at the Tulsa labs. I was able to leverage my knowledge of light propagation to the elastic case. And ham radio with the assistance of my boss who translated geophysical jargon into EE jargon which I understood.

I worked 9 months as a processor and 9 months as an interpreter before I got my first and only 2 week training course in Tulsa. Despite my geology background I was enthralled by signal processing and took off in that direction. There were two choices for a PhD, Austin and Stanford. I didn't like the idea of living in a densely populated area prone to earthquakes and chose Austin.
That cost me my doctorate precisely as a professor friend of the family warned me after my first semester when I related some anecdote of my dealings with Milo Backus. I stayed the course and proved him right. At 36 I could not afford to spend 6 more years working under Claerbout at Stanford and went to work at ARCO. After 4 years with Milo I knew all the major figures in the industry and the Stanford SEP graduates and was under no illusion if a quick passage under Jon.

Have Fun!
Reg

On Saturday, July 6, 2024 at 10:41:02 PM CDT, Mike Feher <n4fs@...> wrote:

Wow, Reg, you must be a lot older than I am (79). I started working on DSP stuff in the late 60’s and I was only in my early 20’s then. My career spans 50 years of working on signal processing, whether it be analog or digital. Been a ham for over 60 years and I never had any desire to try any of the digital modes. I preferred CW, SSB or AM. Left the DSP stuff for work. 73 – Mike

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

Re: Some questions on digital filter design

#362

开云体育

Agree, Dave. 73 – Mike

?

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of David Kirkby
Sent: Sunday, July 7, 2024 6:39 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design

?

On Sun, 7 Jul 2024 at 04:41, Mike Feher via <n4fs=[email protected]> wrote:

Wow, Reg, you must be a lot older than I am (79). I started working on DSP stuff in the late 60’s and I was only in my early 20’s then. My career spans 50 years of working on signal processing, whether it be analog or digital.

?

Having had a WhatApp video chat with Reg, I am pretty sure he is not much older than 79, and I would guess a bit younger.?

Been a ham for over 60 years and I never had any desire to try any of the digital modes. I preferred CW, SSB or AM. Left the DSP stuff for work. 73 – Mike

?

The digital modes have never interested me. I would prefer to use my ears and brain rather than an ADC and CPU.?

?
Mike B. Feher, N4FS

?

Dave G8WRB

Re: Some questions on digital filter design

#361

开云体育

Nice reply, Reg, thanks. I was just wondering since you were talking about all sorts of processing that you said “we” were doing back in the 50’s and the 60’s. So, by “we” you meant people/industry in general. Looking back, my actual DSP work started in the late 60’s and continued till I retired in 2016. My last 30 years were more in the advisory mode than actual design. I still think the Weaver approach would be the best for your tunable filter.? Believe Rabiner & Gold had a comprehensive article in the IEEE way before their book came out. Referred to it often. Also when the Remez exchange algorithm resurfaced was a game changer. I remember when QEX started. Paul Rinaldo lived the next town over from me, when I lived in VA. He asked me to do a paper on digital filters. I did and he said it was too math heavy and asked me instead to present the main principles to a local radio club. I did, and most were rolling their eyes or were just plain bored. That totally turned me off to the idea of QEX. Best wishes with your quest. 73 – Mike

?

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Reginald Beardsley via groups.io
Sent: Sunday, July 7, 2024 8:03 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design

?

LoL :-)

No, Mike, I'm only 71. I have a large library and a lifelong habit of reading the original papers and monographs, e.g. Shannon, Weiner et al. I've discovered quite a few citations which were incorrect. My BA is in English lit and my MS in igneous petrology. In those days I could read 600-800 wpm.

In January 1982 I accepted an offer from Amoco to take up geophysics with the promise of extensive training in Tulsa. I had so much fun taking Calculus I that I took II, III and Differential Equations. Very rare for a geologist to learn mathematics at that level. It's changed a bit since, but it was still a primarily descriptive discipline then.

That was actually my only option as the mining sector was in such a deep slump that all the North American mines were closed except for Sudburry complex. In April I received a letter informing me that my offer was rescinded if I didn't report for work on 21 May. I defended on a typescript, drove to New Orleans and locked my keys in the car in front of the Hyatt next to the Amoco offices.

Upon reporting for work the next morning I was informed that my formal training was delayed indefinitely and given a pile of Western field tapes from the late '60s which I was to reprocess through to final migration, the operation that collapses the diffraction hyperbolae of point diffractors to a point. I was provided 2 books. "Reflection Seismology" by Waters, 2nd ed and "Seismic Exploration Fundamentals" by Coffeen. I bought a copy of "Geophysical Data Analysis" by Robinson and Treitel and borrowed a copy of "Time Sequence Analysis in Geophysics" by Kanassewich from the company library. Evenings and weekends I used them to teach myself the rudiments, assisted greatly by my first boss who was an EE and had worked as a programmer at the Tulsa labs. I was able to leverage my knowledge of light propagation to the elastic case. And ham radio with the assistance of my boss who translated geophysical jargon into EE jargon which I understood.

I worked 9 months as a processor and 9 months as an interpreter before I got my first and only 2 week training course in Tulsa. Despite my geology background I was enthralled by signal processing and took off in that direction. There were two choices for a PhD, Austin and Stanford. I didn't like the idea of living in a densely populated area prone to earthquakes and chose Austin.
That cost me my doctorate precisely as a professor friend of the family warned me after my first semester when I related some anecdote of my dealings with Milo Backus. I stayed the course and proved him right. At 36 I could not afford to spend 6 more years working under Claerbout at Stanford and went to work at ARCO. After 4 years with Milo I knew all the major figures in the industry and the Stanford SEP graduates and was under no illusion if a quick passage under Jon.

Have Fun!
Reg

On Saturday, July 6, 2024 at 10:41:02 PM CDT, Mike Feher <n4fs@...> wrote:

Wow, Reg, you must be a lot older than I am (79). I started working on DSP stuff in the late 60’s and I was only in my early 20’s then. My career spans 50 years of working on signal processing, whether it be analog or digital. Been a ham for over 60 years and I never had any desire to try any of the digital modes. I preferred CW, SSB or AM. Left the DSP stuff for work. 73 – Mike

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

Re: Some questions on digital filter design

#360

LoL :-)

No, Mike, I'm only 71. I have a large library and a lifelong habit of reading the original papers and monographs, e.g. Shannon, Weiner et al. I've discovered quite a few citations which were incorrect. My BA is in English lit and my MS in igneous petrology. In those days I could read 600-800 wpm.

In January 1982 I accepted an offer from Amoco to take up geophysics with the promise of extensive training in Tulsa. I had so much fun taking Calculus I that I took II, III and Differential Equations. Very rare for a geologist to learn mathematics at that level. It's changed a bit since, but it was still a primarily descriptive discipline then.

That was actually my only option as the mining sector was in such a deep slump that all the North American mines were closed except for Sudburry complex. In April I received a letter informing me that my offer was rescinded if I didn't report for work on 21 May. I defended on a typescript, drove to New Orleans and locked my keys in the car in front of the Hyatt next to the Amoco offices.

Upon reporting for work the next morning I was informed that my formal training was delayed indefinitely and given a pile of Western field tapes from the late '60s which I was to reprocess through to final migration, the operation that collapses the diffraction hyperbolae of point diffractors to a point. I was provided 2 books. "Reflection Seismology" by Waters, 2nd ed and "Seismic Exploration Fundamentals" by Coffeen. I bought a copy of "Geophysical Data Analysis" by Robinson and Treitel and borrowed a copy of "Time Sequence Analysis in Geophysics" by Kanassewich from the company library. Evenings and weekends I used them to teach myself the rudiments, assisted greatly by my first boss who was an EE and had worked as a programmer at the Tulsa labs. I was able to leverage my knowledge of light propagation to the elastic case. And ham radio with the assistance of my boss who translated geophysical jargon into EE jargon which I understood.

I worked 9 months as a processor and 9 months as an interpreter before I got my first and only 2 week training course in Tulsa. Despite my geology background I was enthralled by signal processing and took off in that direction. There were two choices for a PhD, Austin and Stanford. I didn't like the idea of living in a densely populated area prone to earthquakes and chose Austin.
That cost me my doctorate precisely as a professor friend of the family warned me after my first semester when I related some anecdote of my dealings with Milo Backus. I stayed the course and proved him right. At 36 I could not afford to spend 6 more years working under Claerbout at Stanford and went to work at ARCO. After 4 years with Milo I knew all the major figures in the industry and the Stanford SEP graduates and was under no illusion if a quick passage under Jon.

Have Fun!
Reg

Show quoted text

On Saturday, July 6, 2024 at 10:41:02 PM CDT, Mike Feher <n4fs@...> wrote:

Wow, Reg, you must be a lot older than I am (79). I started working on DSP stuff in the late 60’s and I was only in my early 20’s then. My career spans 50 years of working on signal processing, whether it be analog or digital. Been a ham for over 60 years and I never had any desire to try any of the digital modes. I preferred CW, SSB or AM. Left the DSP stuff for work. 73 – Mike

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

Re: Some questions on digital filter design

#359

On Sun, 7 Jul 2024 at 04:41, Mike Feher via <n4fs=[email protected]> wrote:

Wow, Reg, you must be a lot older than I am (79). I started working on DSP stuff in the late 60’s and I was only in my early 20’s then. My career spans 50 years of working on signal processing, whether it be analog or digital.

Having had a WhatApp video chat with Reg, I am pretty sure he is not much older than 79, and I would guess a bit younger.?

Been a ham for over 60 years and I never had any desire to try any of the digital modes. I preferred CW, SSB or AM. Left the DSP stuff for work. 73 – Mike

The digital modes have never interested me. I would prefer to use my ears and brain rather than an ADC and CPU.?

?
Mike B. Feher, N4FS

Dave G8WRB

Re: Some questions on digital filter design

#358

开云体育

Wow, Reg, you must be a lot older than I am (79). I started working on DSP stuff in the late 60’s and I was only in my early 20’s then. My career spans 50 years of working on signal processing, whether it be analog or digital. Been a ham for over 60 years and I never had any desire to try any of the digital modes. I preferred CW, SSB or AM. Left the DSP stuff for work. 73 – Mike

?

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Reginald Beardsley via groups.io
Sent: Saturday, July 6, 2024 9:05 PM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design

?

In the days of pure analog data acquisition, Texas Instruments was the instrument manufacturing subsidiary of Geophysical Services Inc. GSI's sole peer was Western Geophysical Inc.

TI developed the first ADC in 1958 and fielded the DFS I (Digital Field System) in 1960. (c.f. "Engineering the World", SMU Press 2005, p. 17). Milo Backus was head of research at GSI and led the development of the early seismic software, despite knowing nothing about computers. He was *very* good at mathematics.

On one occasion at Austin between 1985 and 1989 Milo spent several hours trying to process some data himself before giving up and resuming assigning such tasks to slave labor (grad students). I did not personally witness it, but at least two members of the SEER consortium that Milo ran to support us did and commented on it with great amusement for all.

It would be impossible to say how much TI system data I dealt with vs later competitors. Suffice it to say it didn't take long for lots of companies to start buying ADCs from TI and building recording systems.

TI didn't fare well in the "supercomputer" business. I'd never even heard they attempted it. Convex was king along with IBM vector machines. Though a DEC 11/780 with an FPS 120B array processor was the bog standard seismic processing machine in the '80s for smaller companies. The major (sole in 1989?) commercial package DISCO was written for that configuration. The last time I looked at the DISCO source code 20 odd years ago it was still littered with conditional FPS 120B AP calls.

Have Fun!
Reg

_

Re: Some questions on digital filter design

#357

In the days of pure analog data acquisition, Texas Instruments was the instrument manufacturing subsidiary of Geophysical Services Inc. GSI's sole peer was Western Geophysical Inc.

TI developed the first ADC in 1958 and fielded the DFS I (Digital Field System) in 1960. (c.f. "Engineering the World", SMU Press 2005, p. 17). Milo Backus was head of research at GSI and led the development of the early seismic software, despite knowing nothing about computers. He was *very* good at mathematics.

On one occasion at Austin between 1985 and 1989 Milo spent several hours trying to process some data himself before giving up and resuming assigning such tasks to slave labor (grad students). I did not personally witness it, but at least two members of the SEER consortium that Milo ran to support us did and commented on it with great amusement for all.

It would be impossible to say how much TI system data I dealt with vs later competitors. Suffice it to say it didn't take long for lots of companies to start buying ADCs from TI and building recording systems.

TI didn't fare well in the "supercomputer" business. I'd never even heard they attempted it. Convex was king along with IBM vector machines. Though a DEC 11/780 with an FPS 120B array processor was the bog standard seismic processing machine in the '80s for smaller companies. The major (sole in 1989?) commercial package DISCO was written for that configuration. The last time I looked at the DISCO source code 20 odd years ago it was still littered with conditional FPS 120B AP calls.

Have Fun!
Reg

On Saturday, July 6, 2024 at 02:10:48 PM CDT, Mike N2MS <mstangelo@...> wrote:

Reg,

Did you do any work with Texas Instruments or their equipment? In the early 1980's one of our managers visited TI in Dallas. They showed him what he described as a "Supercomputer", using ECL logic, that was used in seismic research.

Enjoy your discussions.

Mike N2MS

> On 07/06/2024 1:51 PM EDT Reginald Beardsley via groups.io <pulaskite@...> wrote:
>
>
> At which point the oil industry had been doing digital processing of seismic data for years as we could live with 4 ms sample rates. Our peak signal was at best 30-35 Hz. Still is as the earth is the same.
>
> My introduction to seismic processing was a bunch of late '60's marine data that Amoco wanted to reprocess. The improvement in computing resources resulted in stunning improvements in the images. Those tapes also taught me a lot about cracking hex dumps of data from weird recording systems. One set of tapes was an experimental format Western Geophysical used briefly. The tip off was "ROM 14" on the observer notes. When I called Western after numerous failed demux attempts, I mentioned that. The reply was "Wait a few minutes." He came back, gave me the missing information and I was able to demux the data.
>
> Have Fun!
> Reg

Re: Some questions on digital filter design

#356

A website that hosts PDFs. My google query was (with the inner quotes):

“digital signal processing "frerking" pdf”

Without the inner quotes google thinks you mean “freaking”.

Hope this helps and may IA win their lawsuit so I can go back to borrowing from their library.

Show quoted text

On Sat, Jul 6, 2024 at 7:10?PM Dave Daniel via <kc0wjn=[email protected]> wrote:

What is "pdfcoffee"?

DaveD
KC0WJN

==============================
All spelling mistakes are the responsibilty of the reader (Rick Renz, STK, ca. 1994)
==============================

On Jul 6, 2024, at 20:09, Mark LaPlante via <mcpderez=[email protected]> wrote:

?
It’s available on pdfcoffee.

On Sat, Jul 6, 2024 at 3:21?PM Jerry via <jerry=[email protected]> wrote:
I always considered Frerking to be the king of communications signal processing but the books are currently out of sight.? I realized his ALC in SHARC code and it ended up in a couple radios.? Might be available on scribd?
?
Digital Signal Processing in Communications Systems
?
From: Chuck Harris
Sent: Saturday, July 6, 2024 10:28 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design
?
Is it really a breach of causality if the output
that displays the breach doesn't actually occur
until some processing delay after the input that
caused the output?
?
I remember discussing this stuff at length some 50
years ago in a class on linear systems.... all I
remember is discussing it, not what we decided, nor
how we got there.
?
I do recall that simplicity in the math required
that certain apparently non-causal things would
appear in the results.
?
There is a whole lot of blue ink underlining way
too much, in the section on convolution of the
impulse function, and causality, in my copy of
Linear Systems Analysis by Liu & Liu... which, for
me, usually meant I was hopelessly confused...
?
-Chuck Harris
?
?
On Sat, 6 Jul 2024 16:37:12 +0000 (UTC) "Reginald Beardsley via
" <pulaskite=[email protected]> wrote:
> ?This?is?a?general?reply?to?Jeff,?Mike?and?Dave.?I?initially?looked
> at:
>
> Digital?Design?Handbook
> Fred?J.?Taylor
> Marcel?Dekker?1983
>
> Digital?Signal?Processing
> Oppenheim?and?Shafer
> Prentice-Hall?1975
>
> Theory?and?Application?of?Digital?Signal?Processing
> Rabiner?and?Gold
> Prentice-Hall?1975
>
> Digital?Signal?Processing?with?Kernel?Method
> Rojo-Alvarez?et?al
> Wiley/IEEE?2018
>
> Advanced?Digital?Signal?Processing
> and?Noise?Reduction
> Vaseghi
> Wiley?4th?ed?2008
>
> ?Subsequent?to?the?responses?I?checked:
>
> Spectral?Analysis?and?Time?Series
> Priestly
> Academic?Press?1981
>
> Continuous?a?Signals?and?System?Analysis?and?Discrete
> McGillem?and?Cooper
> Holt,?Reinhart?and?Winston?1974
>
> None?of?them?properly?discuss?the?issue?of?causality.
>
> I?did?NOT?look?at?any?of?the?many?monographs?by?Enders?Robinson,
> Robinson?&?Treitel?or?John?H.?Karl?as?I?know?they?have?the?matter
> stated?very?clearly.?Robinson?and?Treitel?were?members?of?Norbert
> Weiner's?Geophysical?Analysis?Group?at?MIT?and?founded?the?entire
> basis?of?DSP.?I?spent?4?years?at?UT?Austin?under?another?member?of
> the?GAG,?Milo?Backus.?Robinson?performed?the?first?digital
> deconvolution?problem?in?1952?using?pencil,?paper?and?a?desk
> calculator.??Robinson?has?pride?of?place?as?the?first?person?to?apply
> DSP?to?data.
>
> Causality?requires?that?the?real?and?imaginary?parts?be?a?Hilbert
> transform?pair.?This?is?well?stated?in:
>
> The?Fourier?Integral?and?Some?of?Its?Applications
> Ronald?Bracewell
> McGraw-Hill?2nd?ed?1978
>
> Causality?simply?states?that?there?is?no?output?prior?to?the?input.
> If?a?filter?is?not?causal?it?produces?output?before?the?event.?The?EE
> community?appears?to?consistently?label?a?zero?phase?signal?as?linear
> phase?with?a?phase?delay.?As?Bracewell?provides?a?proof?and?I?spent?2
> semesters?studying?Churchill's?"Operational?Mathematics"?under?Bill
> Guy?in?"Integral?Transforms"?at?Austin?in?addition?to?the?semester?I
> spent?with?Bracewell?in?"Linear?Systems",?if?the?EE?community?wants
> to?redefine?the?math?they?may.?I?shall?stick?to?what?the
> mathematicians?wrote.
>
> Have?Fun!
> Reg
>
>
>
>
>
?
?
?
?
?
?

Re: Some questions on digital filter design

#355

开云体育

What is "pdfcoffee"?

DaveD

KC0WJN

==============================

All spelling mistakes are the responsibilty of the reader (Rick Renz, STK, ca. 1994)

==============================

Show quoted text

On Jul 6, 2024, at 20:09, Mark LaPlante via groups.io <mcpderez@...> wrote:

?
It’s available on pdfcoffee.

On Sat, Jul 6, 2024 at 3:21?PM Jerry via <jerry=[email protected]> wrote:
I always considered Frerking to be the king of communications signal processing but the books are currently out of sight.? I realized his ALC in SHARC code and it ended up in a couple radios.? Might be available on scribd?
?
Digital Signal Processing in Communications Systems
?
From: Chuck Harris
Sent: Saturday, July 6, 2024 10:28 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design
?
Is it really a breach of causality if the output
that displays the breach doesn't actually occur
until some processing delay after the input that
caused the output?
?
I remember discussing this stuff at length some 50
years ago in a class on linear systems.... all I
remember is discussing it, not what we decided, nor
how we got there.
?
I do recall that simplicity in the math required
that certain apparently non-causal things would
appear in the results.
?
There is a whole lot of blue ink underlining way
too much, in the section on convolution of the
impulse function, and causality, in my copy of
Linear Systems Analysis by Liu & Liu... which, for
me, usually meant I was hopelessly confused...
?
-Chuck Harris
?
?
On Sat, 6 Jul 2024 16:37:12 +0000 (UTC) "Reginald Beardsley via
" <pulaskite=[email protected]> wrote:
> ?This?is?a?general?reply?to?Jeff,?Mike?and?Dave.?I?initially?looked
> at:
>
> Digital?Design?Handbook
> Fred?J.?Taylor
> Marcel?Dekker?1983
>
> Digital?Signal?Processing
> Oppenheim?and?Shafer
> Prentice-Hall?1975
>
> Theory?and?Application?of?Digital?Signal?Processing
> Rabiner?and?Gold
> Prentice-Hall?1975
>
> Digital?Signal?Processing?with?Kernel?Method
> Rojo-Alvarez?et?al
> Wiley/IEEE?2018
>
> Advanced?Digital?Signal?Processing
> and?Noise?Reduction
> Vaseghi
> Wiley?4th?ed?2008
>
> ?Subsequent?to?the?responses?I?checked:
>
> Spectral?Analysis?and?Time?Series
> Priestly
> Academic?Press?1981
>
> Continuous?a?Signals?and?System?Analysis?and?Discrete
> McGillem?and?Cooper
> Holt,?Reinhart?and?Winston?1974
>
> None?of?them?properly?discuss?the?issue?of?causality.
>
> I?did?NOT?look?at?any?of?the?many?monographs?by?Enders?Robinson,
> Robinson?&?Treitel?or?John?H.?Karl?as?I?know?they?have?the?matter
> stated?very?clearly.?Robinson?and?Treitel?were?members?of?Norbert
> Weiner's?Geophysical?Analysis?Group?at?MIT?and?founded?the?entire
> basis?of?DSP.?I?spent?4?years?at?UT?Austin?under?another?member?of
> the?GAG,?Milo?Backus.?Robinson?performed?the?first?digital
> deconvolution?problem?in?1952?using?pencil,?paper?and?a?desk
> calculator.??Robinson?has?pride?of?place?as?the?first?person?to?apply
> DSP?to?data.
>
> Causality?requires?that?the?real?and?imaginary?parts?be?a?Hilbert
> transform?pair.?This?is?well?stated?in:
>
> The?Fourier?Integral?and?Some?of?Its?Applications
> Ronald?Bracewell
> McGraw-Hill?2nd?ed?1978
>
> Causality?simply?states?that?there?is?no?output?prior?to?the?input.
> If?a?filter?is?not?causal?it?produces?output?before?the?event.?The?EE
> community?appears?to?consistently?label?a?zero?phase?signal?as?linear
> phase?with?a?phase?delay.?As?Bracewell?provides?a?proof?and?I?spent?2
> semesters?studying?Churchill's?"Operational?Mathematics"?under?Bill
> Guy?in?"Integral?Transforms"?at?Austin?in?addition?to?the?semester?I
> spent?with?Bracewell?in?"Linear?Systems",?if?the?EE?community?wants
> to?redefine?the?math?they?may.?I?shall?stick?to?what?the
> mathematicians?wrote.
>
> Have?Fun!
> Reg
>
>
>
>
>
?
?
?
?
?
?

Re: Some questions on digital filter design

#354

It’s available on pdfcoffee.

Show quoted text

On Sat, Jul 6, 2024 at 3:21?PM Jerry via <jerry=[email protected]> wrote:

I always considered Frerking to be the king of communications signal processing but the books are currently out of sight.? I realized his ALC in SHARC code and it ended up in a couple radios.? Might be available on scribd?
?
Digital Signal Processing in Communications Systems
?
From: Chuck Harris
Sent: Saturday, July 6, 2024 10:28 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design
?
Is it really a breach of causality if the output
that displays the breach doesn't actually occur
until some processing delay after the input that
caused the output?
?
I remember discussing this stuff at length some 50
years ago in a class on linear systems.... all I
remember is discussing it, not what we decided, nor
how we got there.
?
I do recall that simplicity in the math required
that certain apparently non-causal things would
appear in the results.
?
There is a whole lot of blue ink underlining way
too much, in the section on convolution of the
impulse function, and causality, in my copy of
Linear Systems Analysis by Liu & Liu... which, for
me, usually meant I was hopelessly confused...
?
-Chuck Harris
?
?
On Sat, 6 Jul 2024 16:37:12 +0000 (UTC) "Reginald Beardsley via
" <pulaskite=[email protected]> wrote:
> ?This?is?a?general?reply?to?Jeff,?Mike?and?Dave.?I?initially?looked
> at:
>
> Digital?Design?Handbook
> Fred?J.?Taylor
> Marcel?Dekker?1983
>
> Digital?Signal?Processing
> Oppenheim?and?Shafer
> Prentice-Hall?1975
>
> Theory?and?Application?of?Digital?Signal?Processing
> Rabiner?and?Gold
> Prentice-Hall?1975
>
> Digital?Signal?Processing?with?Kernel?Method
> Rojo-Alvarez?et?al
> Wiley/IEEE?2018
>
> Advanced?Digital?Signal?Processing
> and?Noise?Reduction
> Vaseghi
> Wiley?4th?ed?2008
>
> ?Subsequent?to?the?responses?I?checked:
>
> Spectral?Analysis?and?Time?Series
> Priestly
> Academic?Press?1981
>
> Continuous?a?Signals?and?System?Analysis?and?Discrete
> McGillem?and?Cooper
> Holt,?Reinhart?and?Winston?1974
>
> None?of?them?properly?discuss?the?issue?of?causality.
>
> I?did?NOT?look?at?any?of?the?many?monographs?by?Enders?Robinson,
> Robinson?&?Treitel?or?John?H.?Karl?as?I?know?they?have?the?matter
> stated?very?clearly.?Robinson?and?Treitel?were?members?of?Norbert
> Weiner's?Geophysical?Analysis?Group?at?MIT?and?founded?the?entire
> basis?of?DSP.?I?spent?4?years?at?UT?Austin?under?another?member?of
> the?GAG,?Milo?Backus.?Robinson?performed?the?first?digital
> deconvolution?problem?in?1952?using?pencil,?paper?and?a?desk
> calculator.??Robinson?has?pride?of?place?as?the?first?person?to?apply
> DSP?to?data.
>
> Causality?requires?that?the?real?and?imaginary?parts?be?a?Hilbert
> transform?pair.?This?is?well?stated?in:
>
> The?Fourier?Integral?and?Some?of?Its?Applications
> Ronald?Bracewell
> McGraw-Hill?2nd?ed?1978
>
> Causality?simply?states?that?there?is?no?output?prior?to?the?input.
> If?a?filter?is?not?causal?it?produces?output?before?the?event.?The?EE
> community?appears?to?consistently?label?a?zero?phase?signal?as?linear
> phase?with?a?phase?delay.?As?Bracewell?provides?a?proof?and?I?spent?2
> semesters?studying?Churchill's?"Operational?Mathematics"?under?Bill
> Guy?in?"Integral?Transforms"?at?Austin?in?addition?to?the?semester?I
> spent?with?Bracewell?in?"Linear?Systems",?if?the?EE?community?wants
> to?redefine?the?math?they?may.?I?shall?stick?to?what?the
> mathematicians?wrote.
>
> Have?Fun!
> Reg
>
>
>
>
>
?
?
?
?
?
?

Re: Some questions on digital filter design

#353

FWIW I derived the reflection response for a source and receiver at arbitrary locations in plane layered media via Z transform for a class exercise. Shortly after I wrote that Treitel and Gutowski published the same thing in Geophysics. A classmate joked I should start submitting my homework to Geophysics. I really like the Z transform because the notation is so tractable.

Have Fun!
Reg

On Saturday, July 6, 2024 at 01:49:14 PM CDT, Jeff Anderson <jca1955@...> wrote:

The book I used in school was "Analog and Digital Filters:? Design and Realization", by Harry Y-F. Lam.? The last three chapters introduce the z-transform and then discuss the design and realization of FIR and IIR digital filters based upon the z-transform.

I thought it was an excellent text, but we were using it in manuscript form, pre-publishing, and in a sense we were its proof-readers.

- Jeff, k6jca

On Saturday, July 6, 2024 at 10:42:12 AM PDT, Reginald Beardsley via groups.io <pulaskite@...> wrote:

Dan,

I'm not looking for simple, I'm looking for meticulously correct. I have a small book, "A Handbook of Fourier Theorems" by Champeney which I *always* consult when I am working on the fringes. This is not close to the fringes.

The Fourier integral extends from -infinity to infinity. The EE delay is the result of substituting dirac(t-tau) for the correct dirac(t) when computing the impulse response.

Have Fun!
Reg

On Saturday, July 6, 2024 at 12:03:33 PM CDT, Daniel Marks <profdc9@...> wrote:

If you want something simple to implement you can use what I did in the fldigi version of SCAMP:

look at the?

int scamp::rx_process(const double *buf, int len)

method.? It implements a simple circular buffer filter, which has a sinc-like response but its frequency may be moved around dynamically.? I use a different approach in my guitar pedal code:

for example look at the "DSP_TYPE_WAH" filter effect.? This uses a dynamically changed bandpass filter based on the position of a foot pedal, and does some simple interpolation to move the center frequency around by changing the coefficients of a digital biquad filter.?

All digital filters are implemented with a delay, and so none are "noncausal."? There is a compromise between group delay, which is the amount of lag that the filter applies to the signal and the sharpness of the filter.? A "minimum phase" filter minimizes this delay and has the property that the real and imaginary parts are related by the Hilbert transform.? A filter can be expressed as a cascade of a minimum phase filter and an all-pass filter.

Dan

Show quoted text

On Sat, Jul 6, 2024 at 8:54?AM Reginald Beardsley via <pulaskite=[email protected]> wrote:

I?am?working?on?numerical?modeling?of?CCW?and?am?at?the?point?that?I?need?to?write?the?code?to?implement?twin?pass?band?tuning.??As?this?is?NOT?seismic?processing?I?pulled?a?small?stack?of?my?EE?DSP?classics?and?started?reading?them.

I?have?always?found?the?descriptions?of?digital?filter?design?in?the?EE?literature?baffling?complex.??As?seismic?is?done?in?recorded?time?it?has?a?great?deal?of?latitude?in?implementation?that?a?real?time?DSP?implementation??lacks.??So?I?presumed?that?the?reason?lay?in?the?real?time?constraint.

Yesterday?I?realized?that?the?design??of?a?static?filter?is?completely?trivial.??Specify?the?frequency?domain?characteristics?and?back?transform?to?the?time?domain.??The?impulse?response?is?the?taps?for?any?arbitrary?filter.??I?also?noticed?that?the?filters?in?the?examples?were?zero?phase?filters.

In?seismic?we?always?use?zero?phase?(aka?"linear?phase"?in?EE?jargon)??filters?as?interpreting?a?symmetric?waveform?is?much?easier.

The?first?step?in?seismic?processing?is?called?"designature".??This?consists?of?using?a?recording?of?the??system?impulse?response?to?create?an?all?pass?filter?which?removes?the?phase?imposed?by?causality.??Typically?the?recording?system?impulse?response?is?measured?and??then?the?phase?of?the?source?is?recorded?for?marine?work?using?arrays?of?air?guns.

Analog?filters?are?minimum?phase?as?are?all?physical?processes.??But?the?digital?design?examples?I?saw?were?zero?phase?with?a?symmetric?impulse?response.??This?leads?to?a?non-physical?result.??The?filter?output?begins?*before*?the?input?arrives.??I?find?that?rather?hard?to?justify?in?a?communication?system.??A?quick?check?of?the?indices?revealed?that?except?for?a?very?brief?mention?of?minimum?phase?and?causality?the?issue?is?completely?ignored.??Oppenheim?and?Schafer?devote?a?few?page?and?Rabiner??and?Gold?a?paragraph?before?dismissing?the?matter.? Another text made no mention of it at all.

Would?a?DSO?which?responded?to?an?impulse?showing?the?trace?varying?*before*?the?peak?of?the?impulse?be?acceptable???I?can't?imagine?why?anyone?would?accept?that.

So?why?should?it?be?acceptable?in?a?communication?system???Can?anyone?elucidate?the?matter?

Have?Fun!
Reg

Re: Some questions on digital filter design

#352

开云体育

I always considered Frerking to be the king of communications signal processing but the books are currently out of sight.? I realized his ALC in SHARC code and it ended up in a couple radios.? Might be available on scribd?

?

Digital Signal Processing in Communications Systems https://a.co/d/03jpwjgr

?

Show quoted text

From: Chuck Harris
Sent: Saturday, July 6, 2024 10:28 AM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design

?

Is it really a breach of causality if the output

that displays the breach doesn't actually occur

until some processing delay after the input that

caused the output?

?

I remember discussing this stuff at length some 50

years ago in a class on linear systems.... all I

remember is discussing it, not what we decided, nor

how we got there.

?

I do recall that simplicity in the math required

that certain apparently non-causal things would

appear in the results.

?

There is a whole lot of blue ink underlining way

too much, in the section on convolution of the

impulse function, and causality, in my copy of

Linear Systems Analysis by Liu & Liu... which, for

me, usually meant I was hopelessly confused...

?

-Chuck Harris

?

On Sat, 6 Jul 2024 16:37:12 +0000 (UTC) "Reginald Beardsley via

groups.io" <pulaskite@...> wrote:

> ?This?is?a?general?reply?to?Jeff,?Mike?and?Dave.?I?initially?looked

> at:

>

> Digital?Design?Handbook

> Fred?J.?Taylor

> Marcel?Dekker?1983

>

> Digital?Signal?Processing

> Oppenheim?and?Shafer

> Prentice-Hall?1975

>

> Theory?and?Application?of?Digital?Signal?Processing

> Rabiner?and?Gold

> Prentice-Hall?1975

>

> Digital?Signal?Processing?with?Kernel?Method

> Rojo-Alvarez?et?al

> Wiley/IEEE?2018

>

> Advanced?Digital?Signal?Processing

> and?Noise?Reduction

> Vaseghi

> Wiley?4th?ed?2008

>

> ?Subsequent?to?the?responses?I?checked:

>

> Spectral?Analysis?and?Time?Series

> Priestly

> Academic?Press?1981

>

> Continuous?a?Signals?and?System?Analysis?and?Discrete

> McGillem?and?Cooper

> Holt,?Reinhart?and?Winston?1974

>

> None?of?them?properly?discuss?the?issue?of?causality.

>

> I?did?NOT?look?at?any?of?the?many?monographs?by?Enders?Robinson,

> Robinson?&?Treitel?or?John?H.?Karl?as?I?know?they?have?the?matter

> stated?very?clearly.?Robinson?and?Treitel?were?members?of?Norbert

> Weiner's?Geophysical?Analysis?Group?at?MIT?and?founded?the?entire

> basis?of?DSP.?I?spent?4?years?at?UT?Austin?under?another?member?of

> the?GAG,?Milo?Backus.?Robinson?performed?the?first?digital

> deconvolution?problem?in?1952?using?pencil,?paper?and?a?desk

> calculator.??Robinson?has?pride?of?place?as?the?first?person?to?apply

> DSP?to?data.

>

> Causality?requires?that?the?real?and?imaginary?parts?be?a?Hilbert

> transform?pair.?This?is?well?stated?in:

>

> The?Fourier?Integral?and?Some?of?Its?Applications

> Ronald?Bracewell

> McGraw-Hill?2nd?ed?1978

>

> Causality?simply?states?that?there?is?no?output?prior?to?the?input.

> If?a?filter?is?not?causal?it?produces?output?before?the?event.?The?EE

> community?appears?to?consistently?label?a?zero?phase?signal?as?linear

> phase?with?a?phase?delay.?As?Bracewell?provides?a?proof?and?I?spent?2

> semesters?studying?Churchill's?"Operational?Mathematics"?under?Bill

> Guy?in?"Integral?Transforms"?at?Austin?in?addition?to?the?semester?I

> spent?with?Bracewell?in?"Linear?Systems",?if?the?EE?community?wants

> to?redefine?the?math?they?may.?I?shall?stick?to?what?the

> mathematicians?wrote.

>

> Have?Fun!

> Reg

>

?

Re: Some questions on digital filter design

#351

Reg,

Did you do any work with Texas Instruments or their equipment? In the early 1980's one of our managers visited TI in Dallas. They showed him what he described as a "Supercomputer", using ECL logic, that was used in seismic research.

Enjoy your discussions.

Mike N2MS

Show quoted text

On 07/06/2024 1:51 PM EDT Reginald Beardsley via groups.io <pulaskite@...> wrote:

At which point the oil industry had been doing digital processing of seismic data for years as we could live with 4 ms sample rates. Our peak signal was at best 30-35 Hz. Still is as the earth is the same. 

My introduction to seismic processing was a bunch of late '60's marine data that Amoco wanted to reprocess. The improvement in computing resources resulted in stunning improvements in the images. Those tapes also taught me a lot about cracking hex dumps of data from weird recording systems. One set of tapes was an experimental format Western Geophysical used briefly. The tip off was "ROM 14" on the observer notes. When I called Western after numerous failed demux attempts, I mentioned that. The reply was "Wait a few minutes." He came back, gave me the missing information and I was able to demux the data.

Have Fun!
Reg

Re: Some questions on digital filter design

Daniel Marks

#350

A lot of papers have been written and ink spilled over misapprehension as to what group delay means.? Lots of press about "signals arriving before they were sent."? They'll say anything these days to get you to click.

It does not imply some magic suspension of causality.? Negative group delay only occurs for very small bandwidths, such that the impulse response width is longer in time than the negative group delay.? Certainly interesting phenomena happen in these narrow bandwidth regions (for example a negative index of refraction) but these are only time harmonic responses which take a sufficient amount of time to set up.

But I think this digression into causality misses the point when discussing communication.? The time-domain signals corresponding to the symbols span a linear subspace and have distances apart (for example Euclidean or Hamming distances).? Of course these signals must be causal.? A pure sinusoidal waveform is not causal.? So if one is using a filter bank to separate frequencies, one has to decide how to handle finite-time sinusoids (for example Gaussian envelopes or cyclic prefixes).

Because the signal processing computation can be a limiting factor in real-time processing, this basis is sometimes partially determine by the signals that can be more readily processed.? For example, FFT / OFDM is an example of exploiting symmetry in the filters.? Of course, with a filter bank with only a few frequencies, it might make more sense to use a small number of FIR or IIR filters. ?

There's a lot that is determined by the specifics of what the goals are and what the available computational resources are.? A modern PC has an enormous amount of processing power to be used on a 2.5 kHz wide SSB signal.? Some examples of QRSS using very long convolutional codes have been able to nearly approach the limit of -1.59 dB Eb/N0.

Dan

Show quoted text

On Sat, Jul 6, 2024 at 12:28?PM Chuck Harris via <cfharris=[email protected]> wrote:

Is it really a breach of causality if the output
that displays the breach doesn't actually occur
until some processing delay after the input that
caused the output?

I remember discussing this stuff at length some 50
years ago in a class on linear systems.... all I
remember is discussing it, not what we decided, nor
how we got there.

I do recall that simplicity in the math required
that certain apparently non-causal things would
appear in the results.

There is a whole lot of blue ink underlining way
too much, in the section on convolution of the
impulse function, and causality, in my copy of
Linear Systems Analysis by Liu & Liu... which, for
me, usually meant I was hopelessly confused...

-Chuck Harris

On Sat, 6 Jul 2024 16:37:12 +0000 (UTC) "Reginald Beardsley via
" <pulaskite=[email protected]> wrote:
> ?This?is?a?general?reply?to?Jeff,?Mike?and?Dave.?I?initially?looked
> at:
>
> Digital?Design?Handbook
> Fred?J.?Taylor
> Marcel?Dekker?1983
>
> Digital?Signal?Processing
> Oppenheim?and?Shafer
> Prentice-Hall?1975
>
> Theory?and?Application?of?Digital?Signal?Processing
> Rabiner?and?Gold
> Prentice-Hall?1975
>
> Digital?Signal?Processing?with?Kernel?Method
> Rojo-Alvarez?et?al
> Wiley/IEEE?2018
>
> Advanced?Digital?Signal?Processing
> and?Noise?Reduction
> Vaseghi
> Wiley?4th?ed?2008
>
> ?Subsequent?to?the?responses?I?checked:
>
> Spectral?Analysis?and?Time?Series
> Priestly
> Academic?Press?1981
>
> Continuous?a?Signals?and?System?Analysis?and?Discrete
> McGillem?and?Cooper
> Holt,?Reinhart?and?Winston?1974
>
> None?of?them?properly?discuss?the?issue?of?causality.
>
> I?did?NOT?look?at?any?of?the?many?monographs?by?Enders?Robinson,
> Robinson?&?Treitel?or?John?H.?Karl?as?I?know?they?have?the?matter
> stated?very?clearly.?Robinson?and?Treitel?were?members?of?Norbert
> Weiner's?Geophysical?Analysis?Group?at?MIT?and?founded?the?entire
> basis?of?DSP.?I?spent?4?years?at?UT?Austin?under?another?member?of
> the?GAG,?Milo?Backus.?Robinson?performed?the?first?digital
> deconvolution?problem?in?1952?using?pencil,?paper?and?a?desk
> calculator.??Robinson?has?pride?of?place?as?the?first?person?to?apply
> DSP?to?data.
>
> Causality?requires?that?the?real?and?imaginary?parts?be?a?Hilbert
> transform?pair.?This?is?well?stated?in:
>
> The?Fourier?Integral?and?Some?of?Its?Applications
> Ronald?Bracewell
> McGraw-Hill?2nd?ed?1978
>
> Causality?simply?states?that?there?is?no?output?prior?to?the?input.
> If?a?filter?is?not?causal?it?produces?output?before?the?event.?The?EE
> community?appears?to?consistently?label?a?zero?phase?signal?as?linear
> phase?with?a?phase?delay.?As?Bracewell?provides?a?proof?and?I?spent?2
> semesters?studying?Churchill's?"Operational?Mathematics"?under?Bill
> Guy?in?"Integral?Transforms"?at?Austin?in?addition?to?the?semester?I
> spent?with?Bracewell?in?"Linear?Systems",?if?the?EE?community?wants
> to?redefine?the?math?they?may.?I?shall?stick?to?what?the
> mathematicians?wrote.
>
> Have?Fun!
> Reg
>
>
>
>
>

Re: Some questions on digital filter design

#349

The book I used in school was "Analog and Digital Filters:? Design and Realization", by Harry Y-F. Lam.? The last three chapters introduce the z-transform and then discuss the design and realization of FIR and IIR digital filters based upon the z-transform.

I thought it was an excellent text, but we were using it in manuscript form, pre-publishing, and in a sense we were its proof-readers.

- Jeff, k6jca

On Saturday, July 6, 2024 at 10:42:12 AM PDT, Reginald Beardsley via groups.io <pulaskite@...> wrote:

Dan,

I'm not looking for simple, I'm looking for meticulously correct. I have a small book, "A Handbook of Fourier Theorems" by Champeney which I *always* consult when I am working on the fringes. This is not close to the fringes.

The Fourier integral extends from -infinity to infinity. The EE delay is the result of substituting dirac(t-tau) for the correct dirac(t) when computing the impulse response.

Have Fun!
Reg

On Saturday, July 6, 2024 at 12:03:33 PM CDT, Daniel Marks <profdc9@...> wrote:

If you want something simple to implement you can use what I did in the fldigi version of SCAMP:

look at the?

int scamp::rx_process(const double *buf, int len)

method.? It implements a simple circular buffer filter, which has a sinc-like response but its frequency may be moved around dynamically.? I use a different approach in my guitar pedal code:

for example look at the "DSP_TYPE_WAH" filter effect.? This uses a dynamically changed bandpass filter based on the position of a foot pedal, and does some simple interpolation to move the center frequency around by changing the coefficients of a digital biquad filter.?

All digital filters are implemented with a delay, and so none are "noncausal."? There is a compromise between group delay, which is the amount of lag that the filter applies to the signal and the sharpness of the filter.? A "minimum phase" filter minimizes this delay and has the property that the real and imaginary parts are related by the Hilbert transform.? A filter can be expressed as a cascade of a minimum phase filter and an all-pass filter.

Dan

Show quoted text

On Sat, Jul 6, 2024 at 8:54?AM Reginald Beardsley via <pulaskite=[email protected]> wrote:

I?am?working?on?numerical?modeling?of?CCW?and?am?at?the?point?that?I?need?to?write?the?code?to?implement?twin?pass?band?tuning.??As?this?is?NOT?seismic?processing?I?pulled?a?small?stack?of?my?EE?DSP?classics?and?started?reading?them.

I?have?always?found?the?descriptions?of?digital?filter?design?in?the?EE?literature?baffling?complex.??As?seismic?is?done?in?recorded?time?it?has?a?great?deal?of?latitude?in?implementation?that?a?real?time?DSP?implementation??lacks.??So?I?presumed?that?the?reason?lay?in?the?real?time?constraint.

Yesterday?I?realized?that?the?design??of?a?static?filter?is?completely?trivial.??Specify?the?frequency?domain?characteristics?and?back?transform?to?the?time?domain.??The?impulse?response?is?the?taps?for?any?arbitrary?filter.??I?also?noticed?that?the?filters?in?the?examples?were?zero?phase?filters.

In?seismic?we?always?use?zero?phase?(aka?"linear?phase"?in?EE?jargon)??filters?as?interpreting?a?symmetric?waveform?is?much?easier.

The?first?step?in?seismic?processing?is?called?"designature".??This?consists?of?using?a?recording?of?the??system?impulse?response?to?create?an?all?pass?filter?which?removes?the?phase?imposed?by?causality.??Typically?the?recording?system?impulse?response?is?measured?and??then?the?phase?of?the?source?is?recorded?for?marine?work?using?arrays?of?air?guns.

Analog?filters?are?minimum?phase?as?are?all?physical?processes.??But?the?digital?design?examples?I?saw?were?zero?phase?with?a?symmetric?impulse?response.??This?leads?to?a?non-physical?result.??The?filter?output?begins?*before*?the?input?arrives.??I?find?that?rather?hard?to?justify?in?a?communication?system.??A?quick?check?of?the?indices?revealed?that?except?for?a?very?brief?mention?of?minimum?phase?and?causality?the?issue?is?completely?ignored.??Oppenheim?and?Schafer?devote?a?few?page?and?Rabiner??and?Gold?a?paragraph?before?dismissing?the?matter.? Another text made no mention of it at all.

Would?a?DSO?which?responded?to?an?impulse?showing?the?trace?varying?*before*?the?peak?of?the?impulse?be?acceptable???I?can't?imagine?why?anyone?would?accept?that.

So?why?should?it?be?acceptable?in?a?communication?system???Can?anyone?elucidate?the?matter?

Have?Fun!
Reg

Re: Some questions on digital filter design

#348

See my earlier comment about the definition of the Fourier transform and the impulse response.

On Saturday, July 6, 2024 at 12:28:57 PM CDT, Chuck Harris <cfharris@...> wrote:

Is it really a breach of causality if the output
that displays the breach doesn't actually occur
until some processing delay after the input that
caused the output?

I remember discussing this stuff at length some 50
years ago in a class on linear systems.... all I
remember is discussing it, not what we decided, nor
how we got there.

I do recall that simplicity in the math required
that certain apparently non-causal things would
appear in the results.

There is a whole lot of blue ink underlining way
too much, in the section on convolution of the
impulse function, and causality, in my copy of
Linear Systems Analysis by Liu & Liu... which, for
me, usually meant I was hopelessly confused...

-Chuck Harris

Show quoted text

On Sat, 6 Jul 2024 16:37:12 +0000 (UTC) "Reginald Beardsley via
groups.io" <pulaskite@...> wrote:
> ?This?is?a?general?reply?to?Jeff,?Mike?and?Dave.?I?initially?looked
> at:
>
> Digital?Design?Handbook
> Fred?J.?Taylor
> Marcel?Dekker?1983
>
> Digital?Signal?Processing
> Oppenheim?and?Shafer
> Prentice-Hall?1975
>
> Theory?and?Application?of?Digital?Signal?Processing
> Rabiner?and?Gold
> Prentice-Hall?1975
>
> Digital?Signal?Processing?with?Kernel?Method
> Rojo-Alvarez?et?al
> Wiley/IEEE?2018
>
> Advanced?Digital?Signal?Processing
> and?Noise?Reduction
> Vaseghi
> Wiley?4th?ed?2008
>
> ?Subsequent?to?the?responses?I?checked:
>
> Spectral?Analysis?and?Time?Series
> Priestly
> Academic?Press?1981
>
> Continuous?a?Signals?and?System?Analysis?and?Discrete
> McGillem?and?Cooper
> Holt,?Reinhart?and?Winston?1974
>
> None?of?them?properly?discuss?the?issue?of?causality.
>
> I?did?NOT?look?at?any?of?the?many?monographs?by?Enders?Robinson,
> Robinson?&?Treitel?or?John?H.?Karl?as?I?know?they?have?the?matter
> stated?very?clearly.?Robinson?and?Treitel?were?members?of?Norbert
> Weiner's?Geophysical?Analysis?Group?at?MIT?and?founded?the?entire
> basis?of?DSP.?I?spent?4?years?at?UT?Austin?under?another?member?of
> the?GAG,?Milo?Backus.?Robinson?performed?the?first?digital
> deconvolution?problem?in?1952?using?pencil,?paper?and?a?desk
> calculator.??Robinson?has?pride?of?place?as?the?first?person?to?apply
> DSP?to?data.
>
> Causality?requires?that?the?real?and?imaginary?parts?be?a?Hilbert
> transform?pair.?This?is?well?stated?in:
>
> The?Fourier?Integral?and?Some?of?Its?Applications
> Ronald?Bracewell
> McGraw-Hill?2nd?ed?1978
>
> Causality?simply?states?that?there?is?no?output?prior?to?the?input.
> If?a?filter?is?not?causal?it?produces?output?before?the?event.?The?EE
> community?appears?to?consistently?label?a?zero?phase?signal?as?linear
> phase?with?a?phase?delay.?As?Bracewell?provides?a?proof?and?I?spent?2
> semesters?studying?Churchill's?"Operational?Mathematics"?under?Bill
> Guy?in?"Integral?Transforms"?at?Austin?in?addition?to?the?semester?I
> spent?with?Bracewell?in?"Linear?Systems",?if?the?EE?community?wants
> to?redefine?the?math?they?may.?I?shall?stick?to?what?the
> mathematicians?wrote.
>
> Have?Fun!
> Reg
>
>
>
>
>

Re: Some questions on digital filter design

#347

At which point the oil industry had been doing digital processing of seismic data for years as we could live with 4 ms sample rates. Our peak signal was at best 30-35 Hz. Still is as the earth is the same.

My introduction to seismic processing was a bunch of late '60's marine data that Amoco wanted to reprocess. The improvement in computing resources resulted in stunning improvements in the images. Those tapes also taught me a lot about cracking hex dumps of data from weird recording systems. One set of tapes was an experimental format Western Geophysical used briefly. The tip off was "ROM 14" on the observer notes. When I called Western after numerous failed demux attempts, I mentioned that. The reply was "Wait a few minutes." He came back, gave me the missing information and I was able to demux the data.

Have Fun!
Reg

On Saturday, July 6, 2024 at 12:22:19 PM CDT, Mike Feher <n4fs@...> wrote:

Most of my DSP work was in the early 70's using discrete chips. It was not even called DSP then. Built both FIT and IIR filters. At the time chips and DACs and ADCs were slow. That was OK as we were working on detecting and classifying submarine signals at acoustic frequencies. In fact, the first couple of filters that I built used serial arithmetic using chips from Rockwell Collins. Things got a lot nicer when AMD came out with parallel multipliers. All my filters were built with cascaded second order sections of the Elliptic design. Also, we used the Weaver method to make them tunable. Regards - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
908-902-3831

Show quoted text

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Reginald Beardsley via groups.io
Sent: Saturday, July 6, 2024 12:37 PM
To: [email protected]
Subject: Re: [qex] Some questions on digital filter design

This is a general reply to Jeff, Mike and Dave. I initially looked at:

Digital Design Handbook
Fred J. Taylor
Marcel Dekker 1983

Digital Signal Processing
Oppenheim and Shafer
Prentice-Hall 1975

Theory and Application of Digital Signal Processing Rabiner and Gold Prentice-Hall 1975

Digital Signal Processing with Kernel Method Rojo-Alvarez et al Wiley/IEEE 2018

Advanced Digital Signal Processing
and Noise Reduction
Vaseghi
Wiley 4th ed 2008

Subsequent to the responses I checked:

Spectral Analysis and Time Series
Priestly
Academic Press 1981

Continuous a Signals and System Analysis and Discrete McGillem and Cooper Holt, Reinhart and Winston 1974

None of them properly discuss the issue of causality.

I did NOT look at any of the many monographs by Enders Robinson, Robinson & Treitel or John H. Karl as I know they have the matter stated very clearly. Robinson and Treitel were members of Norbert Weiner's Geophysical Analysis Group at MIT and founded the entire basis of DSP. I spent 4 years at UT Austin under another member of the GAG, Milo Backus. Robinson performed the first digital deconvolution problem in 1952 using pencil, paper and a desk calculator.? Robinson has pride of place as the first person to apply DSP to data.

Causality requires that the real and imaginary parts be a Hilbert transform pair. This is well stated in:

The Fourier Integral and Some of Its Applications Ronald Bracewell McGraw-Hill 2nd ed 1978

Causality simply states that there is no output prior to the input. If a filter is not causal it produces output before the event. The EE community appears to consistently label a zero phase signal as linear phase with a phase delay. As Bracewell provides a proof and I spent 2 semesters studying Churchill's "Operational Mathematics" under Bill Guy in "Integral Transforms" at Austin in addition to the semester I spent with Bracewell in "Linear Systems", if the EE community wants to redefine the math they may. I shall stick to what the mathematicians wrote.

Have Fun!
Reg

Re: Some questions on digital filter design

#346

Dan,

I'm not looking for simple, I'm looking for meticulously correct. I have a small book, "A Handbook of Fourier Theorems" by Champeney which I *always* consult when I am working on the fringes. This is not close to the fringes.

The Fourier integral extends from -infinity to infinity. The EE delay is the result of substituting dirac(t-tau) for the correct dirac(t) when computing the impulse response.

Have Fun!
Reg

On Saturday, July 6, 2024 at 12:03:33 PM CDT, Daniel Marks <profdc9@...> wrote:

If you want something simple to implement you can use what I did in the fldigi version of SCAMP:

look at the?

int scamp::rx_process(const double *buf, int len)

method.? It implements a simple circular buffer filter, which has a sinc-like response but its frequency may be moved around dynamically.? I use a different approach in my guitar pedal code:

for example look at the "DSP_TYPE_WAH" filter effect.? This uses a dynamically changed bandpass filter based on the position of a foot pedal, and does some simple interpolation to move the center frequency around by changing the coefficients of a digital biquad filter.?

All digital filters are implemented with a delay, and so none are "noncausal."? There is a compromise between group delay, which is the amount of lag that the filter applies to the signal and the sharpness of the filter.? A "minimum phase" filter minimizes this delay and has the property that the real and imaginary parts are related by the Hilbert transform.? A filter can be expressed as a cascade of a minimum phase filter and an all-pass filter.

Dan

Show quoted text

On Sat, Jul 6, 2024 at 8:54?AM Reginald Beardsley via <pulaskite=[email protected]> wrote:

I?am?working?on?numerical?modeling?of?CCW?and?am?at?the?point?that?I?need?to?write?the?code?to?implement?twin?pass?band?tuning.??As?this?is?NOT?seismic?processing?I?pulled?a?small?stack?of?my?EE?DSP?classics?and?started?reading?them.

I?have?always?found?the?descriptions?of?digital?filter?design?in?the?EE?literature?baffling?complex.??As?seismic?is?done?in?recorded?time?it?has?a?great?deal?of?latitude?in?implementation?that?a?real?time?DSP?implementation??lacks.??So?I?presumed?that?the?reason?lay?in?the?real?time?constraint.

Yesterday?I?realized?that?the?design??of?a?static?filter?is?completely?trivial.??Specify?the?frequency?domain?characteristics?and?back?transform?to?the?time?domain.??The?impulse?response?is?the?taps?for?any?arbitrary?filter.??I?also?noticed?that?the?filters?in?the?examples?were?zero?phase?filters.

In?seismic?we?always?use?zero?phase?(aka?"linear?phase"?in?EE?jargon)??filters?as?interpreting?a?symmetric?waveform?is?much?easier.

The?first?step?in?seismic?processing?is?called?"designature".??This?consists?of?using?a?recording?of?the??system?impulse?response?to?create?an?all?pass?filter?which?removes?the?phase?imposed?by?causality.??Typically?the?recording?system?impulse?response?is?measured?and??then?the?phase?of?the?source?is?recorded?for?marine?work?using?arrays?of?air?guns.

Analog?filters?are?minimum?phase?as?are?all?physical?processes.??But?the?digital?design?examples?I?saw?were?zero?phase?with?a?symmetric?impulse?response.??This?leads?to?a?non-physical?result.??The?filter?output?begins?*before*?the?input?arrives.??I?find?that?rather?hard?to?justify?in?a?communication?system.??A?quick?check?of?the?indices?revealed?that?except?for?a?very?brief?mention?of?minimum?phase?and?causality?the?issue?is?completely?ignored.??Oppenheim?and?Schafer?devote?a?few?page?and?Rabiner??and?Gold?a?paragraph?before?dismissing?the?matter.? Another text made no mention of it at all.

Would?a?DSO?which?responded?to?an?impulse?showing?the?trace?varying?*before*?the?peak?of?the?impulse?be?acceptable???I?can't?imagine?why?anyone?would?accept?that.

So?why?should?it?be?acceptable?in?a?communication?system???Can?anyone?elucidate?the?matter?

Have?Fun!
Reg

Re: Some questions on digital filter design

#345

Be happy I left out the list of books by Robinson, et al. And the 2D image processing monographs of which I have a large number.

On Saturday, July 6, 2024 at 12:02:10 PM CDT, Dave Daniel <kc0wjn@...> wrote:

Good answer. But, dang, I now have to peruse those.

DaveD
KC0WJN

==============================
All spelling mistakes are the responsibilty of the reader (Rick Renz, STK, ca. 1994)
==============================

> On Jul 6, 2024, at 12:37, Reginald Beardsley via groups.io <pulaskite@...> wrote:
>
> ? This is a general reply to Jeff, Mike and Dave. I initially looked at:
>
> Digital Design Handbook
> Fred J. Taylor
> Marcel Dekker 1983
>
> Digital Signal Processing
> Oppenheim and Shafer
> Prentice-Hall 1975
>
> Theory and Application of Digital Signal Processing
> Rabiner and Gold
> Prentice-Hall 1975
>
> Digital Signal Processing with Kernel Method
> Rojo-Alvarez et al
> Wiley/IEEE 2018
>
> Advanced Digital Signal Processing
> and Noise Reduction
> Vaseghi
> Wiley 4th ed 2008
>
>? Subsequent to the responses I checked:
>
> Spectral Analysis and Time Series
> Priestly
> Academic Press 1981
>
> Continuous a Signals and System Analysis and Discrete
> McGillem and Cooper
> Holt, Reinhart and Winston 1974
>
> None of them properly discuss the issue of causality.
>
> I did NOT look at any of the many monographs by Enders Robinson, Robinson & Treitel or John H. Karl as I know they have the matter stated very clearly. Robinson and Treitel were members of Norbert Weiner's Geophysical Analysis Group at MIT and founded the entire basis of DSP. I spent 4 years at UT Austin under another member of the GAG, Milo Backus. Robinson performed the first digital deconvolution problem in 1952 using pencil, paper and a desk calculator.? Robinson has pride of place as the first person to apply DSP to data.
>
> Causality requires that the real and imaginary parts be a Hilbert transform pair. This is well stated in:
>
> The Fourier Integral and Some of Its Applications
> Ronald Bracewell
> McGraw-Hill 2nd ed 1978
>
> Causality simply states that there is no output prior to the input. If a filter is not causal it produces output before the event. The EE community appears to consistently label a zero phase signal as linear phase with a phase delay. As Bracewell provides a proof and I spent 2 semesters studying Churchill's "Operational Mathematics" under Bill Guy in "Integral Transforms" at Austin in addition to the semester I spent with Bracewell in "Linear Systems", if the EE community wants to redefine the math they may. I shall stick to what the mathematicians wrote.
>
> Have Fun!
> Reg
>
>
>
>
>