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T — Lossless Transmission Line

The lossless transmission line models a two-port distributed element with a specified characteristic impedance and propagation delay.

Syntax

T<name> <port1+> <port1-> <port2+> <port2-> Z0=<impedance> TD=<delay>
Parameter Description
port1+, port1- Port 1 (input) nodes
port2+, port2- Port 2 (output) nodes
Z0 Characteristic impedance (ohms)
TD Propagation delay (seconds)

Examples

* 50-ohm line with 1ns delay
T1 IN 0 OUT 0 Z0=50 TD=1e-9

* Impedance matching
T2 A 0 B 0 Z0=75 TD=5e-9

Typical Usage

Transmission line with matched load
V1 IN 0 PULSE(0 1 0 0.1n 0.1n 5n 20n)
RS IN LINE_IN 50
T1 LINE_IN 0 LINE_OUT 0 Z0=50 TD=1n
RL LINE_OUT 0 50
.TRAN 0.01n 10n
.SAVE V(LINE_IN) V(LINE_OUT)
.END

Notes

  • The lossless model assumes zero series resistance and zero shunt conductance.
  • For accurate high-frequency modeling, ensure the time step is smaller than the propagation delay.