1 ohm transmission line

for

lines

no

Your simulation does something horrible when you open the switch at

300ns. You also have the full 250A swing at the dI/dt of the output pulse in the power supply. Not good. I also think the PFN and the load should be matched.

What repetition rate do you need? Does the load need to be grounded or could it be balanced?

This doesn't need to fit on a VME board, does it? :-)

Jeroen Belleman

Reply to
Jeroen Belleman
Loading thread data ...

Yeah, z gets inverse on w, so one can push Appcad to its width limits and just scale from there. So, why does Appcad give up?

--
John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

used for

ive

setime

h and the

vaguely

ry

l.

e 2500 feet

y lines

look

ge,

re's no

r

going

.highlandtechnology.com  jlarkin at highlandtechnology dot com

How big a box are you picturing? At the vanderbitl FEL there was a lumped L/C 'storage' line that pulsed the Klystron. (I think it was a few us pulse.) The inductors were coiled sections of copper tubing... maybe 24 of them with adjustable taps. The thing sat in a bath tub sized oil bath. You could only tune it up at low voltage...and of course it would change in mysterious ways at full voltage. No one every let me play with it though.

George H.

Reply to
George Herold

d for

me

d the

uely

00 feet

some of these are in the range at 1.7R

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but of course ridiculously expensive since it is "hifi"

make you own?

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stack or fold and glue

-Lasse

Reply to
langwadt

for

risetime

the

vaguely

2500 feet

lines

look

no

going

Fets are certainly an alternate way to do it, like those IR DirectFets maybe, the ones with tiny source inductances. My pulse duty cycles will be low, numbers like radar, so there won't be enough stored energy to knock over coffee cups or anything like that.

Just connecting to the (un-named) load is a big problem. At, say, 10 amps per ns, every nH adds 10 volts of drop. Which is why a relatively high impedance, high voltage, charged transmission line is interesting.

Past experience:

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John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

for

risetime

lines

look

no

going

That's just the Spice hack. In real life, I'd ground the line, charge it gently, and discharge at very low duty cycle. avalanche transistors, of course.

I also think the PFN and the

It's nice to have a lot of voltage to blast through connection inductances.

Duty cycles will be low, 0.1% maybe. The load could float, I think. I don't know very much about the load or about the customers application or technology. I'm in the phase of scribbling and researching, in advance of visiting some potential customers and trying to look like I know this stuff. That's actually exciting, in a weird scary way.

I wish! It will probably need to be a lot smaller, if only because of that damned speed of light thing.

--
John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

used for

risetime

and the

vaguely

2500 feet

lines

look

no

going

Incwww.highlandtechnology.com  jlarkin at highlandtechnology dot com

The size of, say, a Wonder Bread sandwich.

At the vanderbitl FEL there was a

Pulsed power is fun, like a big Marx or maybe NIF. I get the see them now and then, but only with power off. Bummer.

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John Larkin                  Highland Technology Inc 
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John Larkin

for

the

vaguely

feet

Just considering possibilities, which led to the low-Z tranny line musings.

I've recently got interested in kapton flex lately, for other projects, and I need to learn more about it. Got any good flex fab sources to recommend, like for plated-through rigid-flex stuff?

--
John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

for

the

vaguely

feet

Ok, if it's just for sports I understand. But if under time/space/cost pressure I'd look at the brute force transistor method first. Pulse shaper lines are becoming a thing of the past unless it is an application between darn fast and super darn fast, and where cost is not important.

You could contact these guys:

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Nowadays nearly any reputable PCB house does flex. But AFAIK the only method to make very long lines that way is a "rectangular snake cut" out of a large sheet and then foldovers. But be careful, for some application this is patent-protected.

--
Regards, Joerg 

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Reply to
Joerg

You've made Trinitite!

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"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
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Reply to
Fred Abse

Indeed, it looked just like in the 2nd picture:

formatting link

Thanks. I learned something new today.

--
Regards, Joerg 

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Reply to
Joerg

Indeed. How _does) skin effect affect a microstrip TL behavior?

Parallel micro-coax lines might be better.

Reply to
Spehro Pefhany

and

Pretty much the same way as it always does. After a certain copper weight it won't make too much more sense to add weight.

Possibly. But at the power levels John is contemplating it all has to be beefy.

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Reply to
Joerg

On Mon, 15 Apr 2013 09:02:47 -0700, John Larkin wrote: ...

free book on the subject at:

formatting link

Reply to
Glen Walpert

I had a need to figure out transmission line impedances; the microstrip equations on Wikipedia seemed to work well. Of course, I just needed to know what was wide enough and thin enough: I didn't need to hit a characteristic impedance exactly.

I think that the equation basically depends on a fringe-effect correction for thickness that pretty much goes away as the thickness gets -- um -- thin. At any rate, it makes both intuitive sense, and the equations come out, that for a given thickness with a small thickness to width ratio, the line impedance is pretty much inversely proportional to the width.

So if you had to fine-tune the impedance you could probably make up a couple of test samples, measure, then adjust. I doubt you'd have to do too many iterations before you were getting more impedance variation due to material and method variations than due to the actual dimensions of the metal pieces.

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Reply to
Tim Wescott

for

the

feet

If that's intended to be speaker wire, they are crazy. About the only thing speaker wire can really do badly is add inductance, and those two wide, separated conductors are about as bad as you can do.

--
John Larkin         Highland Technology, Inc 

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Reply to
John Larkin

used for

ve

etime

and the

vaguely

y
.
2500 feet

but they can be glued to a wall and painted over or put under a carpet some even come with adhesive backing, so the WAF is higher ;)

some also mention them for low voltage lighting, I guess for a bunch of LEDs on a ceiling it would quite well, just glue up a grid paint over and connect where you need to

-Lasse

Reply to
langwadt

be used for

drive

risetime

high and the

ng, vaguely

omary

well.

take 2500 feet

r.

elay lines

you look

range,

There's no

your

re going

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at highlandtechnology dot com

and

.highlandtechnology.com  jlarkin at highlandtechnology dot com

Wow... how many amps through this sandwich? What are the magnetic forces involved? Are things gonna flex with the current? (just asking)

George H.

Reply to
George Herold

In most cases I'd agree with you... the high inductance will lead to some treble rolloff. Maybe an OK tradeoff for ease of installation in cases where Spousal Approval Factor and the specifics of the room construction requires that the speaker wiring be surface-mounted but "invisible", but maybe not... I wouldn't use this approach in any but special cases.

I do recall some cases a few years (decades) ago, in which some "high-end" boutique audio power amplifiers were very sensitive to capacitive loading. Stick a long run of high-C-per-foot speaker cable on them, and they'd go unstable and start to oscillate (and might even let the magic blue smoke out). Amps like this would be quite happy with Flatwire, I think... but not if it were folded flat into a low-Z transmission line.

--
Dave Platt                                    AE6EO 
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Reply to
Dave Platt

and

Coax has high breakdown voltage, so is inherently inefficient in storing energy at lower voltages, like my piddly 270 or so. I'd need thin insulation, like kapton flex or thin FR4, to do this.

Micro-coax is pretty lossy at high frequencies. Fifty in parallel would be awkward, too.

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John Larkin                  Highland Technology Inc 
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John Larkin

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