AM modulation index

Sweet?

Only thing I've tried to grow around here was tomatoes... they do quite well in the shade in the entry patio ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

I'll try to be more careful.

The problem with your killfiling people like Phil is that you can't see his posts, so you can't ignore sub-threads that he starts. You see responses, and you have to read them before you realize that he's involved.

I think it's easier to just see and ignore posts from people you don't like or aren't interested in, and ignore the entire rest of that branch.

Or you could do like Guy Macon, and killfile everybody.

John

I hope you mean Phil Allison, not Phil Hobbs. Not that I mean to, err, be detecting your mistakes.

Oh, never mind.

John

ps - Phil Hobbs' book is a good read, practically worth the insane price. If Allison ever wrote a book, it would be composed entirely of four-letter words.

[snip] [snip]

John! Great idea! You solved the problem in a way that Agent could implement!

I've been after the Forte guys for years to filter on content, but you can't do that without downloading bodies.

But headers contain all the thread/sub-thread information.

Marvelous... just kill ANY "descendent" threads!

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Yeah, that would work. PA could then poison a thread, or at least that branch, forever. Even in the rare case where he said something useful, and others took off from there.

Do you have DSL? That changes ones attitude about stuff like this.

John

RARE INDEED!

I've got cable (Cox HSI), 3~5MB/s

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

"John Larkin" = lunatic

** Go chase this troll's rabbits down as many holes as you like.

My comment was completely fair.

....... Phil

"Jim Thompson"

** Troll.

.......... Phil

"John Fields" = a criminal NUT CASE

** I see you missed the point - again.

** Bullshit - his original post gave away nothing of what he was doing.

It was on an inappropriate NG.

My comments were valid.

YOU can go DROP DEAD.

.......... Phil

I couldn't have said it any better. It is indeed an RFID application. I presume you know there are two (passive) kinds in the 134.2 kHz frequency range: FDX transponders, acting as stated, and HDX transponders, (FSK) sending their ID after the carrier has been turned off. The last kind is relatively simple to receive, sample and decode. The FDX gives no problems in a laboratory environment, but in practice, when it is farther away from the transmitter coil, the AM index gets lower and lower. As long as the transponder (and only the transponder) is within a few inches of the antenna all is well, any further than that.... I need to detect it within two feet.

I figured the only thing I could do is to improve the AM index, before sampling. Digitaly, without enhancement, I can go as low as an AM index of

2500 (within my budget), still about a 100 times too low to detect the transponder from two feet. So I need to spice it up a little.

I know there won't come any solution of this Phil character, so let's simply ignore him (it?) and try to solve this. It is in itself an interesting problem and I'm sure there are many more applications if we could figure it out.

Rutger Unprofessional Circuit Designer (just to please our demon)

"Rutger Stoots"

** TROLL.

........ Phil

--
Where the hell did that come from???  I meant "Allison".

Sorry about that.

--
Why not? Everyone else does... Yes, I meant Allison, thanks.

--
No, I didn\'t.

What you were trying to point out, in a hateful way, was that the
content of Stoots\' post labeled him as a novice.

"Rutger Stoots" wrote in message news:4423c195$0$23339$ snipped-for-privacy@text.nova.planet.nl...

[snip]

I was tinkering with LTSpice and cobbled together a filter and amplifier arrangement that seems to work; the 1.5mV

1KHz pulses burried in the 250V 100KHz signal end up as a 1V p-p zero-centered signal. The circuit takes about 5ms to settle down after turn-on.

I used a simple multi-stage passive low-pass filter to initially cut the 250V signal down to size while preserving most of the 1KHz signal amplitude, and followed that with an active low-pass filter to remove the rest of the "hair" from the signal. The circuit for this filter was obtained from

the "Hi-Cut" filter with a gain of 40 and a cut-off at 2KHz.

After that, a bit of amplification finishes the job.

Here's the LTSpice file:

Version 4 SHEET 1 1476 1236 WIRE -1072 144 -1072 96 WIRE -1072 256 -1072 224 WIRE -1072 416 -1072 336 WIRE -1056 704 -1072 704 WIRE -992 96 -1072 96 WIRE -896 96 -912 96 WIRE -896 192 -896 96 WIRE -896 304 -896 256 WIRE -880 96 -896 96 WIRE -880 704 -912 704 WIRE -880 704 -880 528 WIRE -848 880 -848 736 WIRE -816 528 -880 528 WIRE -800 704 -880 704 WIRE -800 736 -848 736 WIRE -784 96 -800 96 WIRE -784 192 -784 96 WIRE -784 304 -784 256 WIRE -768 96 -784 96 WIRE -688 528 -736 528 WIRE -688 720 -736 720 WIRE -688 720 -688 528 WIRE -672 96 -688 96 WIRE -672 192 -672 96 WIRE -672 304 -672 256 WIRE -608 64 -608 -32 WIRE -608 720 -688 720 WIRE -576 64 -608 64 WIRE -576 96 -672 96 WIRE -464 -32 -608 -32 WIRE -464 80 -512 80 WIRE -464 80 -464 -32 WIRE -416 80 -464 80 WIRE -304 -64 -304 -128 WIRE -304 80 -336 80 WIRE -304 80 -304 16 WIRE -304 128 -304 80 WIRE -304 192 -304 176 WIRE -304 256 -304 192 WIRE -272 80 -304 80 WIRE -192 -128 -304 -128 WIRE -192 -32 -192 -128 WIRE -192 80 -192 32 WIRE -192 256 -192 112 WIRE -144 80 -192 80 WIRE -144 112 -192 112 WIRE -32 -128 -192 -128 WIRE -32 64 -32 -128 WIRE -32 96 -80 96 WIRE -32 96 -32 64 WIRE 96 64 -32 64 WIRE 464 336 384 336 WIRE 464 384 464 336 FLAG -1072 416 0 FLAG 464 384 0 FLAG 384 256 +Vcc IOPIN 384 256 Out FLAG 384 416 -Vcc IOPIN 384 416 Out FLAG -896 304 0 FLAG -784 304 0 FLAG -672 304 0 FLAG -544 48 +Vcc IOPIN -544 48 Out FLAG -544 112 -Vcc IOPIN -544 112 Out FLAG 96 64 Vfilt IOPIN 96 64 BiDir FLAG -112 64 +Vcc IOPIN -112 64 Out FLAG -112 128 -Vcc IOPIN -112 128 Out FLAG -304 256 0 FLAG -192 256 0 FLAG -768 688 +Vcc IOPIN -768 688 Out FLAG -768 752 -Vcc IOPIN -768 752 Out FLAG -848 880 0 FLAG -1072 704 Vfilt IOPIN -1072 704 In FLAG -608 720 Vout IOPIN -608 720 Out SYMBOL voltage -1072 128 R0 WINDOW 0 -74 52 Left 0 WINDOW 3 -221 7 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 250 100KHz) SYMBOL voltage -1072 240 R0 WINDOW 0 -74 53 Left 0 WINDOW 3 394 -497 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 1.5ms 5ms 1e-6 1e-6 .5ms 1.0ms 7) SYMBOL voltage 384 240 R0 WINDOW 0 -70 60 Left 0 WINDOW 3 45 50 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 9V SYMBOL voltage 384 320 R0 WINDOW 0 -70 60 Left 0 WINDOW 3 34 54 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V4 SYMATTR Value 9V SYMBOL res -896 80 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 100K SYMBOL res -784 80 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 100K SYMBOL res -672 80 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 100K SYMBOL cap -912 192 R0 SYMATTR InstName C4 SYMATTR Value .001µF SYMBOL cap -800 192 R0 WINDOW 3 25 61 Left 0 SYMATTR Value .001µF SYMATTR InstName C5 SYMBOL cap -688 192 R0 SYMATTR InstName C6 SYMATTR Value .001µF SYMBOL Opamps\\\\LT1028 -544 16 R0 SYMATTR InstName U1 SYMBOL Opamps\\\\LT1028 -112 32 R0 SYMATTR InstName U2 SYMBOL cap -320 128 R0 SYMATTR InstName C1 SYMATTR Value 836nF SYMBOL cap -208 -32 R0 SYMATTR InstName C2 SYMATTR Value 10nF SYMBOL res -320 64 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 139 SYMBOL res -288 32 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R2 SYMATTR Value 6K SYMBOL res -288 96 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R3 SYMATTR Value 135 SYMBOL Opamps\\\\LT1028 -768 656 R0 SYMATTR InstName U3 SYMBOL res -720 512 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R7 SYMATTR Value 2MEG SYMBOL cap -992 688 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C3 SYMATTR Value .01µF SYMBOL res -1008 720 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R8 SYMATTR Value 10K TEXT -1040 -296 Left 0 !.tran 0 20ms 0ms 100ns TEXT -1040 -256 Left 0 ;Behavior of voltage source V2: TEXT -1008 -168 Left 0 ;Initial Low-Pass filtering section TEXT -576 -168 Left 0 ;Buffer TEXT -320 -168 Left 0 ;Active Low-Pass Filter TEXT -976 488 Left 0 ;Amplifier

Why don't you just go and buy modules from SAVI?

Then you can enjoy the benefits of my circuit design ;-)

Obviously I can't tell you what to do, it's proprietary.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Huh? This doesn't even make any sense. It's none of my business what Phil posts; I simply killfile everything from him. But some people insist on responding to his juvenile rantings, and sometimes those people have something constructive to offer, so I hate to filter them just on the grounds that they're occasional trollfeeders.

Hope This Helps! Rich

No, you're right, it's not. Sending pulses and listening in between is how they do radar and sonar, not trying to detect the modulation of a

250V carrier caused by a grain-of-rice RFID.

Maybe he should get some RFID stuff and study it.

And, what's the goal anyway?

Thanks, Rich

--
Sure it does.  I asked Phil a question, and your yenta ass answered
for him, so if I were to ask you a question you\'d be happy with Phil
answering for you?