LT Spice transmission line simulation - factor of 0.5 error?
LT Spice transmission line simulation - factor of 0.5 error?
(OP)
I am trying to use LT Spice to model simple lossless transmission line behavior.
As a test case, I considered the geometry discussed in:
thread239-293269: How long does a Transm Line have to be for TL theory to apply
Specifically, I tried to recreate the results shown on slide slide 4 of attachment to the current post (which is the same as slide 4 of attachment to my previous post 27 Feb 11 13:12).
The system which is modeled is as follows:
[Vs]-[Rs=1]--===[TL1]===--===[TL2]===-===[TL3]===-[RLoad=1]
Vs is a ramp rise with magnitude 1, duration 1
TL1: Zc=1, length unimportant since source is matched
TL3: Zc=1, length unimportant since load is matched
TL2: Zc=3, length corresponds to transit time of 3. It represents the anomaly in impedance due to ferrite sleeve.
The Maple / analytical solution (same as previouis post) is described on page 2 and the pdf embedded in slide 3. The result is plotted on slide 4 and has the expected behavior that the output voltage eventually rises to the input voltage.
The LT Spice solution is shown on attached slides 5 and 6. It has the same shape, but only rises to magnitude 0.5... which must be wrong. More details on the LT spice model are on slides 7 and 8.
Am I missing something or did the LT spice model computes this result incorrectly? If so, why?
As a test case, I considered the geometry discussed in:
thread239-293269: How long does a Transm Line have to be for TL theory to apply
Specifically, I tried to recreate the results shown on slide slide 4 of attachment to the current post (which is the same as slide 4 of attachment to my previous post 27 Feb 11 13:12).
The system which is modeled is as follows:
[Vs]-[Rs=1]--===[TL1]===--===[TL2]===-===[TL3]===-[RLoad=1]
Vs is a ramp rise with magnitude 1, duration 1
TL1: Zc=1, length unimportant since source is matched
TL3: Zc=1, length unimportant since load is matched
TL2: Zc=3, length corresponds to transit time of 3. It represents the anomaly in impedance due to ferrite sleeve.
The Maple / analytical solution (same as previouis post) is described on page 2 and the pdf embedded in slide 3. The result is plotted on slide 4 and has the expected behavior that the output voltage eventually rises to the input voltage.
The LT Spice solution is shown on attached slides 5 and 6. It has the same shape, but only rises to magnitude 0.5... which must be wrong. More details on the LT spice model are on slides 7 and 8.
Am I missing something or did the LT spice model computes this result incorrectly? If so, why?
=====================================
(2B)+(2B)' ?





RE: LT Spice transmission line simulation - factor of 0.5 error?
(PS: I didn't take the time to review the attachment in detail. It's a bit late.)
RE: LT Spice transmission line simulation - factor of 0.5 error?
Problem solved. Thanks.
=====================================
(2B)+(2B)' ?