[SOLVED] TLP generator problem, Help!!!

[prcken]

Hi all
Please help to check the attached schematic of Transmission line pulse generator and its corresponding waveforms at each node.
S1 is a switch controlled by the voltage pulse “swctl” as shown in the picture, when swctl is 0V, S1 is open (huge resistance), when swctl is 1V, S1 is closed (zero resistance).
I have 2 questions:
Q1: why the coaxial cable cannot be recharged to generate a series of pulses? It should be recharged!
Q2: why the voltage at far end of the coaxial cable drops abruptly from 100V to 0? I cannot see a negative reflected waveform.
Thanks
Kehan

 

[prcken]

i set enough time to charge the cable this time, got the waveforms in the attached.
Co in my cable model is 98pF, Rsource is 10Mohm, so the τ is about 10µ for 10m length cable, i need at least 2.3τ time interval to charge the cable up to 90% of Vsource.
the charging time i set is 13.8µs as you can see in the figure. but why the cable is negatively charged for the second round?