# Simple transmission line question

J

#### josephkk

Jan 1, 1970
0
[...]
If the source is a 5 volt step generator with a 50 ohm source
impedance, the initial wave will be 2.5 volts. When it hits the open
end, it will double to be a clean 5 volt step. A 5 volt wave will then
zip back to the generator end and die there when it hits, and it's all
over. Clean 5 volt step at the far end, and the generator voltage sees
100 ohms (50 internal+50 line) as the transient load, 50 mA peak
current.

LT Spice has transmission lines. If you string a bunch together, you
can see what happens at intermediate points.

I'll have to try it. Does LT spice have directional couplers? It'd
be nice to see what's coming and going....

Directional couplers in spice are trivial! Basically, it's nothing
more than a Wheatstone bridge. Replace one of the sides by the tline
and apply twice the signal to the top of the bridge. The reflection
appears across the bridge. Below an LTspice example to play with.

Jeroen Belleman
==================================================
Version 4
SHEET 1 880 680
WIRE 32 112 -320 112
WIRE 224 112 32 112
WIRE 32 144 32 112
WIRE 224 144 224 112
WIRE -320 224 -320 112
WIRE 32 240 32 224
WIRE 128 240 32 240
WIRE 160 240 128 240
WIRE 224 240 224 224
WIRE 336 240 224 240
WIRE 576 240 432 240
WIRE 32 272 32 240
WIRE 336 272 272 272
WIRE 496 272 432 272
WIRE 496 288 496 272
WIRE 576 288 576 240
WIRE 272 304 272 272
WIRE -320 336 -320 304
WIRE 336 352 272 352
WIRE 400 352 336 352
WIRE 32 368 32 352
WIRE 272 368 272 352
WIRE 400 368 400 352
WIRE 224 384 224 240
WIRE 576 384 576 368
WIRE 160 432 160 240
WIRE 224 432 160 432
WIRE 272 464 272 448
WIRE 400 464 400 448
FLAG 272 304 0
FLAG 496 288 0
FLAG 32 368 0
FLAG 576 384 0
FLAG -320 336 0
FLAG 272 464 0
FLAG 400 464 0
FLAG 336 352 reflected
FLAG 128 240 incident
SYMBOL res 16 128 R0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL res 16 256 R0
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL res 208 128 R0
SYMATTR InstName R3
SYMATTR Value 50
SYMBOL tline 384 256 R0
SYMATTR InstName T1
SYMBOL res 560 272 R0
SYMATTR InstName R4
SYMATTR Value 1meg
SYMBOL voltage -320 208 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value PULSE(0 2 10n 1n 1n 10n)
SYMBOL e 272 352 R0
SYMATTR InstName E1
SYMATTR Value 1
SYMBOL res 384 352 R0
SYMATTR InstName R5
SYMATTR Value 1
TEXT 80 40 Left 2 !.tran 200n

Nice. I really like the transhybrid aspect.

?-)

J

Jan 1, 1970
0
B

#### Bill Sloman

Jan 1, 1970
0
Manual stitch bonding is a lost art these days...

"stitch bonding [â€²stich â€šbÃ¤ndÂ·iÅ‹]
(engineering)

A method of making wire connections between two or more points on an
integrated circuit by using impulse welding or heat and pressure while
feeding the connecting wire through a hole in the center of the welding
electrode."
2003 by The McGraw-Hill Companies, Inc.

There was an old wire bonding machine sitting on the loading dock at
Cincinnati Electronics to be sold as scrap. After one look at it, I
could see why it was scrap. It looked like Noah had brought it over on
his Ark.

They had used it to build hybrids, in house.

I suppose there might have been some hybridisation on Noah's Ark - pairs ofevery species might have gone in for foursomes. I hadn't realised that Noah's Ark had made it to the USA, but I suppose that it's no less improbable than the story about it ending up 12,000 feet high on Mount Ararat, surviving a few volcanic eruptions in the intervening millenia.

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