The following file simulates a transmission line inverter. Two transmission line elements are required since two propagation modes are excited. In the case of a coaxial line, the first line (t1) models the inner conductor with respect to the shield, and the second line (t2) models the shield with respect to the outside world.
transmission-line inverter
v1 1 0 pulse(0 1 0 0.1N)
r1 1 2 50
x1 2 0 0 4 tline
r2 4 0 50
.subckt tline 1 2 3 4
t1 1 2 3 4 z0=50 td=1.5ns
t2 2 0 4 0 z0=100 td=1ns
.ends tline
.tran 0.1ns 20ns
.end