Is DSP useful?

[TheWizard]

@Sean - Sorry, I make not analogue, I say you the true from the my attempts ...

@JC1 - What is DSP... Easy, cheap chip, Hard is not DSP, Hard is the people, sponsors, investitors... hard is the lost time in for tests....

ArcTangent, Filters, Delays - sly algoritm or hard math?

[Delbert grady]

DSP DSP DSP

I was talking to Bruce the other day, he says the trouble is there is nothing to go on.
If you arrive at a murder scene and there is absolutely nothing to go on. No evidence at all, then all the DSP in the world wont find the culprit. With metal detection you have a receive signal that changes in some minute way depending if there is metal or what its made of. So you use DSP to get another half inch of depth. Gold and Mercury Atoms are almost the same thing, just one Electron difference and DSP wont see Electrons. I think Bruce has a valid point here.

[TheWizard]

Bruce....

May be this is story like Bill Gates and 640k RAM for PC........ or Gramophone vs CD...
Candy Man
Sorry but is foolishly affirmation....

[Sean_Goddard]

Hi JC1, Well I am neither Junior Engineer nor technician, but I agree with what you say 100%. The quantisation does introduce many errors, but I failt ot see why the DSP radio works BETTER than the analogue one. Perhaps you could explain as I may be missing something.

I don't doubt you are right in every sense, but I'm at a loss to see why any company would spend millions developing systems using DSP (ala Mobile phone technology, Nimrod which can pick up cars on a road 200 miles away) when analogue is obviously a better system, BUT maybe just for the application they have in mind?

[JC1]

Big Errors

Hi JC1, Well I am neither Junior Engineer nor technician, but I agree with what you say 100%. The quantisation does introduce many errors, but I failt ot see why the DSP radio works BETTER than the analogue one. Perhaps you could explain as I may be missing something.

I don't doubt you are right in every sense, but I'm at a loss to see why any company would spend millions developing systems using DSP (ala Mobile phone technology, Nimrod which can pick up cars on a road 200 miles away) when analogue is obviously a better system, BUT maybe just for the application they have in mind?

DSP radio works better?

The Ham / Citizen Band receivers are

still analog with things like Numerical

Controlled Oscillators {fancy dividers}

for the VFO. The Japanese have done

this very well to the point of changing

the master clock in the receiver so that

the fundamental freq or harmonics don't

kill the receiver.

Now there are things which can be done

with Wavelets and Spectrum hopping/multiplexing

and some real interesting stuff.

But implementing something similiar to

a Lock in Amplifier in analog which will

sync pick out signals a 100 + db below

noise floor in

digital and get 60 db is not impressive,

though it may fit better in a cell phone

that is true.

Now I didn't bring up the issue of DSP.

It sounded to me like it was some kind

of a given.

Why I commented.

So the question is simple.

Exactly what are you planning on implementing

in this DSP? That is the real question.

Do you have the time to do the noise

floor reduction routine? and everything else?

And will it even work? Why will it work?

And the computer errors get most exaggerated

by things like multiplications and divisions.

{by numbers other than binary shifting}

In fact the "real" programmers are experts

on preserving the some of the accuracy of the intial data

which can quickly get ruined by an amature hack.

32 bit precision can look like a joke depending

on just how much processing you are doing.

Anyway I'll shut up maybe. But I can tell you for

a fact that Garrett and Whites actually had good

engineers doing this for them. The problem was

this solution looking for a problem which is not

always the solution at all. In some cases it it.

And maybe it is in this case too but some real

evidence of this needs to be brought forward before

the Conclusion is reached that DSP is the given

answer. And just about ALL your forum help is left

out. Now if you want make a "new" "special" device

that is some kinda of a radar or GPR and it sends out

a "chirpped" waveform, well then I can talk that

talk as well, and walk that walk.

Including RF.

I was working Air Defense Radars when

I was an undergrad. 30 years ago.

[JC1]

Business

Business book must read.

One author who apparently knows his audience is Spencer Johnson, whose book Who Moved My Cheese? has been a bestseller since it first appeared in 1998. This very short work boils down to one clever fable, the implications of which are not hard to interpret but which Johnson nonetheless underlines with a thoroughness to suit the meanest capacities. Put simply, people resemble mice who must always be prepared to find a new source of "cheese." Johnson skillfully depicts the discomfort and denial of people who have recently lost their "cheese," but his presentation of how one goes about finding new cheese is a bit trite.

The testimonials praising Johnson's little book are together almost as long as the book itself. They come from prominent people at prominent companies, including BellSouth, Eastman Kodak, NBC, and Xerox. But these are not exactly the most successful companies in the world today. Alas, business books, as these testimonials inadvertently suggest, bear an ambiguous relation to business success. People who merely dream of being big winners in the rat race are the ones actually reading these books; the real winners, the successful entrepreneurs and executives, can't have time for such distractions. Besides, any lessons one might learn from a business bestseller are probably already understood by those who are really good at "finding cheese."

Find the "cheese".

http://www.affdoublethink.com/archiv...oved_my_ch.php

[Qiaozhi]

Business book must read.

One author who apparently knows his audience is Spencer Johnson, whose book Who Moved My Cheese? has been a bestseller since it first appeared in 1998. This very short work boils down to one clever fable, the implications of which are not hard to interpret but which Johnson nonetheless underlines with a thoroughness to suit the meanest capacities. Put simply, people resemble mice who must always be prepared to find a new source of "cheese." Johnson skillfully depicts the discomfort and denial of people who have recently lost their "cheese," but his presentation of how one goes about finding new cheese is a bit trite.

The testimonials praising Johnson's little book are together almost as long as the book itself. They come from prominent people at prominent companies, including BellSouth, Eastman Kodak, NBC, and Xerox. But these are not exactly the most successful companies in the world today. Alas, business books, as these testimonials inadvertently suggest, bear an ambiguous relation to business success. People who merely dream of being big winners in the rat race are the ones actually reading these books; the real winners, the successful entrepreneurs and executives, can't have time for such distractions. Besides, any lessons one might learn from a business bestseller are probably already understood by those who are really good at "finding cheese."

Find the "cheese".

http://www.affdoublethink.com/archiv...oved_my_ch.php

Yes - I've read this book. It's about people's fear of change. Hence the title "Who moved my cheese?".

[JC1]

Yes kinda

The book is about moving when

markets change and companies that

don't fail. Old record albums come to

mind.

More DSP.

Sorry.

DSP radios receive weaker signals

than a comparable analog radio

because they are more "selective"

with their super sharp digital filters.

This is fine as they don't care about

phase of the carrier. These sharp digital filters

have large phase shifts in their

narrow passband, just like an analog

implementation would, and wreak

havoc on phase information.

You can add additional analog filters

to a VLF being careful not to destroy

phase information but you will not gain

much in SNR performance unless you have

an interferring transmitter near your receiver passband.

PI detectors need a wide passband

i.e. 100 Hz to 100 kHz and will not

benefit from sharp digital filters.

Though the group delay destruction

could yield some interesting looking

distorted decay curves.

In my humble opinion.

[TheWizard]

Easy PI DSP test - result is 1 euro at 40 sm(Air) in room with big 50Hz noise....

[Sean_Goddard]

AH, Now I see JC1. Very good points raised there. I've read the book too, EXCELLENT!!

If super narrow DSP filters change the phase info so much, how come QAM64 used for digital television in the UK works so well? And the military radio I ws telking about demods the I and the Q of the signal as each contains separate data (NOT sure I should have said that on the forum).

Don't get me wrong, I'm NOT arguing with you as from your writings you obviously know what you are talking about.

I concur, the trick with DSP is WHAT to do to WHAT. BTW mark Rowan from Whites and I have virtually identical backgrounds, freaky eh?

BTW, I built a chirp detector aboout a year ago using a PIC and a DDS chip and a few other bits, it worked just fine, great sensitivity across the whole range. I've recently updated the design and it now has two Tx channels (four output DDS) one sweeps down, the other up, though I've found at the crossover you have to blank one channel or it overload the front end badly. The output is a sawtooth waveform from the demodulators, this is then nulled by an opposite polarity sawtooth generated by a trigger from the PIC and an analog circuit controlled by digipots and switchable capacitors. A target shows up as a "blip" or "pimple" of the positive going slope of the demod output, or if a large target, an overall increase in DC level on the I and Q channels. It's basically a normal VLF machine with a swept Tx signal. Works very well. I'll dig out the schematics when I get my lab built again after the recent move.

Interesting thing if I remember is that on the "Disc" channel, the amplitude and position of the pimple are dependent of the type of target material. Maybe someone could use this information further and investigate a new discriminate method. I guess it's because things like gold and silver max phase shift at different frequencies.

[Carl-NC]

JC,

I don't understand why all the discussion over DSP. We are not far enough along with this whole Design Group concept to even begin talking about
architectures. It's entirely possible that an eventual design team will decide that DSP is not the right approach. But it's pointless to make that decision now, or even debate it.

- Carl

[Delbert grady]

the wizard

that chip on your board marked DSP what is it and what does it do

[TheWizard]

dsPIC30 @ 30 MIPS
DO ALL:
Create TX pulse
Digital Processing RX
Noise Reduction & False Alarm Detection
Create Sound 300-1300Hz
Keyboard
Graphical Display
Power Control
EEPROM settings
PC communication...

[Delbert grady]

DSP

thank you for you quick and civil reply I will have to look at some of these.

Could you post just a small bit of DSP code.

[TheWizard]

Main.C

it is from this board...