LLTRA - Lossless Transmission Line Model

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Modified by Phil Loughhead on Mar 4, 2014

Model Kind

Transmission Line

Model Sub-Kind

Lossless

SPICE Prefix

SPICE Netlist Template Format

@DESIGNATOR %1 %2 %3 %4 Z0=@"CHAR. IMPEDANCE" ?"TRANSMISSION DELAY"/TD=@"TRANSMISSION DELAY"//F=@FREQUENCY ?"NORMALISED LENGTH"|NL=@"NORMALISED LENGTH"|/ ?"INITIAL VOLTAGE 1"|IC=@"INITIAL VOLTAGE 1", @"INITIAL CURRENT 1", @"INITIAL VOLTAGE 2", @"INITIAL CURRENT 2"|

Parameters (definable at component level)

The following component-level parameters are definable for this model type and are listed on the Parameters tab of the Sim Model dialog. To access this dialog, simply double-click on the entry for the simulation model link in the Models region of the Component Properties dialog.

Char. Impedance	characteristic impedance (in Ohms). (Default = 50).
Transmission Delay	Transmission delay (in seconds). (Default = 10n).
Frequency	frequency (in Hertz).
Normalised Length	normalized electrical length of the transmission line with respect to the wavelength in the line, at the specified frequency.
Port 1 Voltage	time-zero voltage at port 1 of the transmission line (in Volts).
Port 1 Current	time-zero current at port 1 of the transmission line (in Amps).
Port 2 Voltage	time-zero voltage at port 2 of the transmission line (in Volts).
Port 2 Current	time-zero current at port 2 of the transmission line (in Amps).

Notes

The length of the line must be expressed in one of the following two ways:

the Transmission Delay is specified directly (eg, TD=10ns)
a value for the Frequency is specified, together with a value for the Normalised Length.

If a value for Frequency is specified but a value for the Normalised Length is omitted, then 0.25 is assumed (that is, the frequency is assumed to be the quarter-wave frequency).
The values for Port 1 and Port 2 Initial Voltages and Currents only apply if the Use Initial Conditions option is enabled on the Transient/Fourier Analysis Setup page of the Analyses Setup dialog.
The simulation-ready lossless transmission line component (LLTRA) can be found in the Simulation Transmission Line integrated library (\Library\Simulation\Simulation Transmission Line.IntLib).

Examples

Consider the lossless transmission line in the above image, with the following characteristics:

Pin1 (positive node of Port 1) is connected to net IN
Pin2 (negative node of Port 1) is connected to net GND
Pin3 (positive node of Port 2) is connected to net OUT
Pin4 (negative node of Port 2) is connected to net GND
Designator is LLTR1
Char. Impedance = 50Ohms
Transmission Delay = 20ns

The entry in the SPICE netlist would be:

*Schematic Netlist: TLLTR1 IN 0 OUT 0 Z0=50 TD=20NS