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SPICE tarnsient analysis of oscillators - sampling time

Go to the LT Spice HELP and look for O. Lossy line

Try this:

Version 4 SHEET 1 904 680 WIRE -80 96 -128 96 WIRE -48 96 -80 96 WIRE 80 96 32 96 WIRE 160 96 80 96 WIRE 368 96 256 96 WIRE 432 96 368 96 WIRE -128 128 -128 96 WIRE 160 128 112 128 WIRE 288 128 256 128 WIRE 432 128 432 96 WIRE 112 160 112 128 WIRE 288 160 288 128 WIRE -128 240 -128 208 WIRE 432 240 432 208 FLAG 112 160 0 FLAG 288 160 0 FLAG -128 240 0 FLAG 432 240 0 FLAG -80 96 GEN FLAG 80 96 TDR FLAG 368 96 END SYMBOL ltline 208 112 R0 WINDOW 0 -4 -75 Bottom 2 WINDOW 3 -5 -68 Top 2 SYMATTR InstName O1 SYMATTR Value LTR50 SYMBOL voltage -128 112 R0 WINDOW 0 48 73 Left 2 WINDOW 3 33 116 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 1 1n) SYMBOL res 48 80 R90 WINDOW 0 -45 54 VBottom 2 WINDOW 3 -37 53 VTop 2 SYMATTR InstName R1 SYMATTR Value 50 SYMBOL res 416 112 R0 WINDOW 0 53 42 Left 2 WINDOW 3 52 75 Left 2 SYMATTR InstName R2 SYMATTR Value 100 TEXT -96 288 Left 2 !.model LTR50 LTRA(len=10 R=5 L=2.3u C=1n) TEXT 152 224 Left 2 !.tran 10u TEXT 576 128 Left 2 ;TDR of 50 ohm lossy line TEXT 624 168 Left 2 ;DCR = 50 ohms TEXT 640 216 Left 2 ;Td = 470 ns TEXT 616 264 Left 2 ;JL Mar 26, 2017

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin
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If i understand the fundamental problem correctly, y our having an issue simulating at realistic freq. with LTspice? Well let me say this first, your p rogram isn't the only front end with that issue. well - i'd recommend looking at either another program for that specific metric(might as well see if it's unanimous or not too) or adjusting your design. Have you reduced or eliminated anything s uperfluous to this signal path? or the other way can you encapsulate this and use a PLL to eit her maintain freq under load, OR and this still makes my head spacy - you can use a PLL to r un your sim as you were/had it - and clean up / or reduce proportionally the magnitude of your results.

i've seen a lot of strange things happening behind the scenes for a couple programs...I wrote one of them! hahahh...but i wrote it for me and my very specific use. LTspice is no lone wolf...Do you work with Labview? Cadence? Matlab? they're m ore or less the best options im aware of....

sorry i couldnt be more specific - precise operati ons have too many variables

Jasen Betts

Jasen Betts

Lark> >>>>>

Jasen Betts

ev> >>>>>>>>

the frequency error is unmeasurable

Let it run for 1,000 cycles. After

overlap exactly. The frequency

the time step down to get a useful

ulation times silly. There is

be set. When precision matters, I

.

e V source. Run that for 5 seconds

chunky line segments. Change the

lot better.

e using LTSpice with compression on.

Its a solution looking for a problem.

above, is that the LT Spice

sually works fine for things like

tants are nasty.

en I specify a pulse generator

driving a slow RC or something.

ckets inside a transmission

an unlimited amount of

d signal at the other end of the

. it doesn't need separate storage for

is only saved at time-step

ll along the line, so can't

wonder how many effective

whether the time step matters

nd poke a pulse into one

s of reflections, maybe of

forth. There's no "black

lot of internal nodes.

not conducted out of the

of that end node as an

replayed back to the source

lates circuits; it doesn't

appears at the second end

hat doesn't flow into the

the second end and

hm

. It needs internal nodes.

hash of it.

Reply to
A_george

It may use an integral equation for that bit. Chopping the TL up into short sections isn't an efficient solving method.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com
Reply to
Phil Hobbs

I do that with real coax a fair amount. It's good for generating odd pulse trains and so on. with quite decent timing.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com
Reply to
Phil Hobbs

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