AM modulation index

Hey, bud, whatever happened to that SSB 1 GHz mixer you were going to post on ABSE?

Jim

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

--- No, it won't.

There are always people drifting through here who wouldn't be aware that a shun was in place (If one could even get put place, since trying to get everyone here to agree to it would be like trying to herd cats) and Phil would go after them.

--- Grow thicker skin.

-- John Fields Professional Circuit Designer

Don't know actually, but it makes sense.

Meindert

aren't

Oh? And in what way does it differ?

Meindert

"Passive" tags simply rectify to double the frequency.

...Jim Thompson

I didn't see any response besides Larkin responding to Phil Allison's crap.

So I didn't think there was any interest beyond perpetuating flame.

But I'll dig it up and post "it" or "them". "Them" use passive 90° phase shifters and thus have "bandwidth".

"It" used quadrature dividers (for synthesizer use).

...Jim Thompson

On Thu, 23 Mar 2006 20:12:56 +0100, "Meindert Sprang" wrote:

--- An earlier post of mine to Rich Grise explains the difference, at least in the way I understood the OP's meaning.

Because I thought a notch filter centered on 100kHz might be the way to go, I simulated one being driven by a 250VPP source modulated by a 10mV square wave in order to see whether the modulation could be easily recovered. Even with a 120dB notch at 100kHz and perfect components the results weren't too encouragaging, and if you've got Linear's simulator you can run this circuit file to see why:

Version 4 SHEET 1 880 852 WIRE -512 336 -512 112 WIRE -512 512 -512 416 WIRE -512 576 -512 512 WIRE -336 112 -512 112 WIRE -272 416 -272 304 WIRE -272 512 -512 512 WIRE -272 512 -272 496 WIRE -160 304 -272 304 WIRE -160 512 -272 512 WIRE -160 512 -160 352 WIRE -112 112 -256 112 WIRE -112 176 -112 112 WIRE -112 288 -112 256 WIRE -112 512 -160 512 WIRE -112 512 -112 368 WIRE 16 112 -112 112 WIRE 16 656 16 112 WIRE 48 112 16 112 WIRE 48 656 16 656 WIRE 160 112 128 112 WIRE 160 144 160 112 WIRE 160 368 160 208 WIRE 160 512 -112 512 WIRE 160 512 160 368 WIRE 160 560 160 512 WIRE 160 656 112 656 WIRE 160 656 160 640 WIRE 192 112 160 112 WIRE 192 368 160 368 WIRE 208 656 160 656 WIRE 304 112 272 112 WIRE 304 368 272 368 WIRE 304 368 304 112 WIRE 304 656 272 656 WIRE 304 656 304 368 FLAG -512 576 0 SYMBOL res 144 96 R90 WINDOW 0 -52 59 VBottom 0 WINDOW 3 -38 58 VTop 0 SYMATTR InstName R1 SYMATTR Value 1591.55 SYMBOL res 288 96 R90 WINDOW 0 -48 62 VBottom 0 WINDOW 3 -43 61 VTop 0 SYMATTR InstName R2 SYMATTR Value 1591.55 SYMBOL res 176 656 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R3 SYMATTR Value 795.77 SYMBOL cap 144 144 R0 WINDOW 0 -61 31 Left 0 WINDOW 3 -67 61 Left 0 SYMATTR InstName C3 SYMATTR Value 2e-9 SYMBOL cap 112 640 R90 WINDOW 0 70 33 VBottom 0 WINDOW 3 70 34 VTop 0 SYMATTR InstName C1 SYMATTR Value 1e-9 SYMBOL cap 272 640 R90 WINDOW 0 72 33 VBottom 0 WINDOW 3 74 34 VTop 0 SYMATTR InstName C2 SYMATTR Value 1e-9 SYMBOL voltage -512 320 R0 WINDOW 3 24 44 Invisible 0 SYMATTR Value SINE(0 250 100000) SYMATTR Value2 AC 1 SYMATTR InstName V1 SYMBOL res -240 96 R90 WINDOW 0 -39 54 VBottom 0 WINDOW 3 -35 57 VTop 0 SYMATTR InstName R5 SYMATTR Value 10 SYMBOL sw -112 384 M180 WINDOW 0 32 15 Left 0 WINDOW 3 32 44 Left 0 SYMATTR InstName S1 SYMBOL voltage -272 400 R0 WINDOW 39 0 0 Left 0 WINDOW 3 -227 105 Invisible 0 WINDOW 0 -50 6 Left 0 SYMATTR Value PULSE(0 1 0 1e-6 1e-6 .0005 .001) SYMATTR InstName V2 SYMATTR Value2 AC 1 SYMBOL res -128 160 R0 SYMATTR InstName R6 SYMATTR Value 2.4999e5 SYMBOL res 288 352 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R7 SYMATTR Value 1e6 TEXT -474 538 Left 0 !.ac dec 64 10 1e6 TEXT -144 0 Left 0 ;fc = 1/2 pi r1 c1 TEXT -144 32 Left 0 ;R1 = R2 = 2R3 TEXT -144 64 Left 0 ;C1 = C2 = C3/2 TEXT -474 570 Left 0 !;tran 0 .03 .01 TEXT -520 624 Left 0 !.model SW SW(Ron=1 Roff=10Meg Vt=0.5Vh=0)

-- John Fields Professional Circuit Designer

Best regards, Spehro Pefhany

Something here doesn't make any sense. How can you receive with the same antenna while you are transmitting? Exactly what do you think you are really measuring?

If you are measuring voltage at the antenna input with respect to ground and you are seeing millivolt changes when the transponder shorts its own coil, then all you are seeing is a change in the antenna impedance caused by the shorted coil. The change in the antenna impedance causes a small change in the voltage on your transmitter final. Your antenna impedance is the load impedance seen by your transmitter final. That's why everything else also causes a change in what you are seeing.

This is not really amplitude modulation since 100% modulation would imply a zero load resistance (i.e. output voltage equal to zero) and therefore no power transfer at all on negative peaks.

As John points out for metal detectors, you really need a separate receiving apparatus. It should be tuned to the oscillator frequency you are using on your transmitter. I assume your transponder puts out its digital stream at a certain frequency. You could monitor for a bitstream at that frequency. I suspect all you would need is a simple product detector to recover the bitstream.

tim ab0wr

I never see Phil's replies (since I killfile on Phil Allison "as author").

I only see his crap when someone, like Larkin, continues the flame.

Fields, You sure you understand Usenet filtering ?:-)

...Jim Thompson

Posted at.......

Newsgroups: alt.binaries.schematics.electronic Subject: Re: AM modulation index - SSB-Mixer-ExampleForSED.zip Message-ID:

...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 | |

Simple solution: killfile me too.

John

I thought of that, but OCCASIONALLY you have something useful to offer ;-)

...Jim Thompson