Hi all!
I am having the following issue when utilizing the variable TIME with NGSPICE:
When I run the simulation using my old computer (Ubuntu 16 and NGSpice v 32) it works perfectly. Instead, when I ran the same code using Windows 11 and NGSpice v 43, I got nonsense.
As an example, the code I post below utilizes two transmission lines coupled to a time-dependent capacitor. This simple code is enough to see the type of analysis I am trying to make.
See in the link a plot comparing the output of the two respective runs:
https://ibb.co/GR674v0
I hope you can help me understand better the origin of the problem, and hopefully, how to fix it.
Many thanks!
Lucas
*==============================================================
*==============================================================
CODE
*==============================================================
*==============================================================
.title TD Dimer
*==============================================================
*-------------------------------------------------------------
- Parameters…
*--------------------------------------------------------------
.param Ck0 = 96.08436682642376pF
.param Ck1 = 86.47593014378138pF
.param wm = 251.32741228718345kHz
.param freq=215kHz
.param T=1/freq
.param step_time = T/500.
.param end_time = T*100
- Specify some initial node voltages
.ic v(v1)=0 v(v2)=0 $ ic: initial conditions
*==============================================================
*-------------------------------------------------------------- - TIME MODULATED CAPACITOR
*-------------------------------------------------------------- - ASCII SCHEME
-
v1 v2
*====o----||----o==== Transmission Line
-
k(t)
*--------------------------------------------------------------
*--------------------------------------------------------------
- leads (50 Ohm with sources)
*Transmission line 1
Vs1 0 vs1 SIN(0V 1V 215kHz 0s 0Hz)
RZ0_1 vs1 v1 50Ohm
*Transmission line 2
Vs2 vs2 0 SIN(0V 0V 215kHz 0s 0Hz)
RZ0_2 vs2 v2 50Ohm
*--------------------------------------------------------------
- Time modulated capacitor
Ck v1 v2 {Ck0 + Ck1 * cos(wm * TIME)}
*--------------------------------------------------------------
*-------------------------------------------------------------
- Transient analysis specs and control
*-------------------------------------------------------------
.TRAN {step_time} {end_time} UIC
.control
run $ run the file
linearize $ resample all points on steps
plot v(v2) $ plot the oscillator voltage vector
set wr_singlescale $ only print out one time scale
wrdata nodes_v1_v2.dat v(v1),v(v2) $ write
.endc
.END