LT Spice LTRA
John Larkin
Does anybody have an LT Spice schematic (.asc file) that uses the LTRA
lossy transmission line element? When I do it, nothing comes out!
John
BobW
"John Larkin" <jjla...@highNOTlandTHIStechnologyPART.com> wrote in message
news:l4mhj61g2s9uj18n4...@4ax.com...
John,
The transmission lines on the top of the schematic are lossy transmission
lines.
Bob
Version 4
SHEET 1 2584 752
WIRE -608 64 -640 64
WIRE -528 64 -608 64
WIRE -512 64 -528 64
WIRE -320 64 -432 64
WIRE -208 64 -320 64
WIRE 0 64 -112 64
WIRE 112 64 0 64
WIRE 656 64 112 64
WIRE 896 64 752 64
WIRE 1056 64 896 64
WIRE 1392 64 1056 64
WIRE 1648 64 1488 64
WIRE 1808 64 1648 64
WIRE 2144 64 1808 64
WIRE 2400 64 2240 64
WIRE 2416 64 2400 64
WIRE -640 112 -640 64
WIRE 0 128 0 64
WIRE 896 128 896 64
WIRE 1648 128 1648 64
WIRE -208 160 -208 96
WIRE -112 160 -112 96
WIRE 656 160 656 96
WIRE 752 160 752 96
WIRE 1392 160 1392 96
WIRE 1488 160 1488 96
WIRE 2144 160 2144 96
WIRE 2240 160 2240 96
WIRE 2416 160 2416 144
WIRE -528 176 -528 64
WIRE -640 224 -640 192
WIRE -528 272 -528 256
WIRE -384 272 -528 272
WIRE -352 272 -384 272
WIRE 0 288 0 208
WIRE 144 288 0 288
WIRE 400 288 240 288
WIRE 416 288 400 288
WIRE 896 288 896 208
WIRE 1040 288 896 288
WIRE 1296 288 1136 288
WIRE 1312 288 1296 288
WIRE 1648 288 1648 208
WIRE 1792 288 1648 288
WIRE 2048 288 1888 288
WIRE 2064 288 2048 288
WIRE -528 304 -528 272
WIRE 144 384 144 320
WIRE 240 384 240 320
WIRE 416 384 416 368
WIRE 1040 384 1040 320
WIRE 1136 384 1136 320
WIRE 1312 384 1312 368
WIRE 1792 384 1792 320
WIRE 1888 384 1888 320
WIRE 2064 384 2064 368
WIRE -528 416 -528 384
FLAG -640 224 0
FLAG -320 64 PATH_LAUNCH
FLAG 240 384 0
FLAG 416 384 0
FLAG 144 384 0
FLAG 400 288 VIA1_END
FLAG 1136 384 0
FLAG 1312 384 0
FLAG 1040 384 0
FLAG 1296 288 VIA2_END
FLAG 752 160 0
FLAG 656 160 0
FLAG 112 64 VIA1_NODE
FLAG 1056 64 VIA2_NODE
FLAG -608 64 Vsource
FLAG 2416 160 0
FLAG 2400 64 PATH_END
FLAG 1888 384 0
FLAG 2064 384 0
FLAG 1792 384 0
FLAG 2048 288 VIA3_END
FLAG 1808 64 VIA3_NODE
FLAG -528 416 0
FLAG -384 272 Vref
FLAG -112 160 0
FLAG -208 160 0
FLAG 1488 160 0
FLAG 1392 160 0
FLAG 2240 160 0
FLAG 2144 160 0
SYMBOL voltage -640 96 R0
WINDOW 3 -565 -87 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PWL file="auto random pwl data for LTSpice.txt"
SYMATTR InstName V1
SYMBOL res -416 48 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL tline 192 304 R0
WINDOW 3 -73 -71 Left 0
SYMATTR Value Td=15p Z0=50
SYMATTR InstName T2
SYMBOL res 400 272 R0
SYMATTR InstName R3
SYMATTR Value 10000
SYMBOL res -16 112 R0
SYMATTR InstName R4
SYMATTR Value .001
SYMBOL tline 1088 304 R0
WINDOW 3 -73 -71 Left 0
SYMATTR Value Td=14p Z0=50
SYMATTR InstName T1
SYMBOL res 1296 272 R0
SYMATTR InstName R5
SYMATTR Value 10000
SYMBOL res 880 112 R0
SYMATTR InstName R6
SYMATTR Value .001
SYMBOL res 2400 48 R0
SYMATTR InstName R7
SYMATTR Value 50
SYMBOL tline 1840 304 R0
WINDOW 3 -73 -71 Left 0
SYMATTR Value Td=13p Z0=50
SYMATTR InstName T7
SYMBOL res 2048 272 R0
SYMATTR InstName R8
SYMATTR Value 10000
SYMBOL res 1632 112 R0
SYMATTR InstName R9
SYMATTR Value .001
SYMBOL res -544 160 R0
SYMATTR InstName R2
SYMATTR Value 1000
SYMBOL res -544 288 R0
SYMATTR InstName R10
SYMATTR Value 1000
SYMBOL ltline 704 80 R0
WINDOW 38 0 60 Center 0
SYMATTR SpiceModel BobLossyTLine1inch
SYMATTR InstName O1
SYMATTR Value ""
SYMBOL ltline -160 80 R0
WINDOW 38 0 60 Center 0
SYMATTR SpiceModel BobLossyTLine2inch
SYMATTR InstName O2
SYMATTR Value ""
SYMBOL ltline 1440 80 R0
WINDOW 38 0 60 Center 0
SYMATTR SpiceModel BobLossyTLine2inch
SYMATTR InstName O3
SYMATTR Value ""
SYMBOL ltline 2192 80 R0
WINDOW 38 0 60 Center 0
SYMATTR SpiceModel BobLossyTLine3inch
SYMATTR InstName O4
SYMATTR Value ""
TEXT -1192 72 Left 0 !.tran 0 10e-9 0 .1p
TEXT -1192 136 Left 0 !.options baudrate 10e9
TEXT -1208 200 Left 0 ;Data for the PWL file is generated\nby a spreadsheet
called\n"Piecewise linear data generator for LTSpice.xls"
TEXT 448 448 Left 0 !.model BobLossyTLine1inch LTRA(len=1 R={RperInch}
L={LperInch} C={CperInch})
TEXT 456 480 Left 0 !.model BobLossyTLine2inch LTRA(len=2 R={RperInch}
L={LperInch} C={CperInch})
TEXT 456 512 Left 0 !.model BobLossyTLine3inch LTRA(len=3 R={RperInch}
L={LperInch} C={CperInch})
TEXT 464 568 Left 0 !.param RperInch = 0.2*26.9
TEXT 464 608 Left 0 !.param LperInch = 7.978n
TEXT 472 648 Left 0 !.param CperInch = 3.319p
TEXT 960 568 Left 0 ;DEFAULT VALUES for 50ohm stripline:\n0.200
ohms/inch\n7.978 nH/inch\n3.219 pF/inch\nThe skin effect at 10GHZ multiplies
the resistance per inch by a factor of 26.9.\nAlso, the "proximity effect"
additionally multiplies the resistance per inch by\na factor of 1.5 for
anything than a symmetrical stripline.
TEXT -64 576 Left 0 !.step param RperInch LIST 0.200 5.400
TEXT -48 648 Left 0 !.step param CperInch LIST 3.119p 3.319p
TEXT -56 608 Left 0 !.step param LperInch LIST 7.878n 8.078n
John Larkin
<nimby_GI...@roadrunner.com> wrote:
>
>
>"John Larkin" <jjla...@highNOTlandTHIStechnologyPART.com> wrote in message
>news:l4mhj61g2s9uj18n4...@4ax.com...
>> Hi,
>>
>> Does anybody have an LT Spice schematic (.asc file) that uses the LTRA
>> lossy transmission line element? When I do it, nothing comes out!
>>
>> John
>>
>
>John,
>
>The transmission lines on the top of the schematic are lossy transmission
>lines.
>
>Bob
>
>
Yikes! I'd been connecting the signals to the zigzag thing in the
middle, and grounding the plates! That sort of explains not getting
any output.
Thanks
John
Joerg
I was almost gonna say "Is it plugged in?" but then bit my lip :-)
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
John Larkin
wrote:
>John Larkin wrote:
>> On Thu, 20 Jan 2011 18:58:31 -0800, "BobW"
>> <nimby_GI...@roadrunner.com> wrote:
>>
>>>
>>> "John Larkin" <jjla...@highNOTlandTHIStechnologyPART.com> wrote in message
>>> news:l4mhj61g2s9uj18n4...@4ax.com...
>>>> Hi,
>>>>
>>>> Does anybody have an LT Spice schematic (.asc file) that uses the LTRA
>>>> lossy transmission line element? When I do it, nothing comes out!
>>>>
>>>> John
>>>>
>>> John,
>>>
>>> The transmission lines on the top of the schematic are lossy transmission
>>> lines.
>>>
>>> Bob
>>>
>>>
>>
>> Yikes! I'd been connecting the signals to the zigzag thing in the
>> middle, and grounding the plates! That sort of explains not getting
>> any output.
>>
>
>I was almost gonna say "Is it plugged in?" but then bit my lip :-)
I'm too used to PADS, which won't let you leave wires dangling any old
where. If it's not a valid connection, there can't be a line.
John
Joerg
Eagle lets you draw anything. That has a huge advantage: I can draw
timing diagrams, flow charts, mechanical sketches, anything. People have
generated wedding cake templates with it. However, if you hit the ERC
button it'll generate a warning list with all the locations that have
loose ends. LTSpice doesn't :-(
John Larkin
wrote:
Oh, PADS lets me add "2d lines" and text on a schematic, but they
don't conduct electricity. But it won't let me draw a dangling
connection. I remember one version of ORCAD that would tend to
terminate a wire just a pixel or two short of a node, *inside* a
connection dot, so it looked connected but wasn't. PADS won't allow
that. Once you start a connection line, you have to end it on a node
or bail.
You can create an offpage in PADS and never create a mate for it, but
that's easily checked for. PADS will also import/export all (as in
ALL, including decals) of a schematic or PCB in ASCII. I wrote a
couple of PowerBasic programs to do crosschecks of netlists, and one
to check a PCB against our BOM. The Brat loves them.
LT Spice let me apparently connect to graphic-only features of the
delay line symbol, and ran the simulation with no warnings. And no
output! It doesn't seem to mind dangling wires.
Incidentally, the LT Spice delay line model has differential signal
connectivity from one end to the other, but no common-mode
connectivity. So a short lossless delay line behaves like an ideal 1:1
transformer. There must be a use for that.
Version 4
SHEET 1 880 680
WIRE 96 80 32 80
WIRE 400 80 224 80
WIRE 32 112 32 80
WIRE 96 128 96 80
WIRE 128 128 96 128
WIRE 224 128 224 80
WIRE 400 128 400 80
WIRE 128 160 32 160
WIRE 336 160 224 160
WIRE 32 192 32 160
WIRE 336 240 336 160
WIRE 400 240 400 208
WIRE 400 240 336 240
WIRE 32 304 32 272
WIRE 336 304 336 240
FLAG 32 304 0
FLAG 336 304 0
FLAG 32 112 0
SYMBOL tline 176 144 R0
WINDOW 0 -19 -40 Left 0
WINDOW 3 -67 45 Left 0
SYMATTR InstName T1
SYMATTR Value Td=100n Z0=50
SYMBOL voltage 32 176 R0
WINDOW 3 46 103 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value PULSE(0 1 1u)
SYMBOL res 384 112 R0
SYMATTR InstName R1
SYMATTR Value 1
TEXT 128 232 Left 0 !.tran 100u
John
Phil Hobbs
Turn on the connection dots. It's in some menu or other.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
John Larkin
It still allows dangling wires, and apparent connections that aren't.
No big deal, I know now.
John
Joerg
I remember the drill in some Orcad Versions, move every part and see if
all the spaghetti moves as well.
> You can create an offpage in PADS and never create a mate for it, but
> that's easily checked for. PADS will also import/export all (as in
> ALL, including decals) of a schematic or PCB in ASCII. I wrote a
> couple of PowerBasic programs to do crosschecks of netlists, and one
> to check a PCB against our BOM. The Brat loves them.
>
> LT Spice let me apparently connect to graphic-only features of the
> delay line symbol, and ran the simulation with no warnings. And no
> output! It doesn't seem to mind dangling wires.
>
One of the more common mistakes when people use delay lines for the
first time is not connecting the other end to GND (or to somewhere
else). "But I don't have to do that on real coax!"
> Incidentally, the LT Spice delay line model has differential signal
> connectivity from one end to the other, but no common-mode
> connectivity. So a short lossless delay line behaves like an ideal 1:1
> transformer. There must be a use for that.
>
Guilty. I have used TX lines as transformers.
Let your sim below run hi-Z, send short pulses in, and you'll get an
interesting pattern coming out :-)
--