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Transmission Line

Model transmission line

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  • RF Blockset / Circuit Envelope / Elements

  • Transmission Line block

Description

Use the Transmission Line block to model delayed-based, lumped, and distributed transmission lines. Mask dialog box options change automatically to accommodate model type selection.

Parameters

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Main

Type of transmission line model, specified as one of these.

Transmission Line Types Description

Delay-based and lossless

Model transmission line with delay but no loss.

Delay-based transmission line

Delay-based and lossy

Model transmission line with delay and loss.

Delay-based and lossy transmission line

Lumped parameter L-section

Model transmission line with RLGC L-sections.

R,L,G.C is connected as L-section.

Lumped parameter Pi-section

"Model transmission line with RLGC pi-sections.

R,L,G.C is connected as Pi-section.

Coaxial

Model transmission line as a coaxial transmission line. The cross section of a coaxial transmission line is shown in the following figure. Its physical characteristics include the radius of the inner conductor a, and the radius of the outer conductor b.

Coaxial transmission line layers: Inner conductor, dielectric, outer conductor

Coplanar waveguide

Model transmission line as a coplanar waveguide. The cross section of a coplanar waveguide transmission line is shown in the following figure. Its physical characteristics include conductor width w, conductor thickness t, slot width s, substrate height d, and relative permittivity constant ε.

Cross-section of a coplanar waveguide with and without conductor-backed ground plane

Microstrip

Model transmission line as a standard, embedded, inverted, or suspended microstrip transmission line. The cross-sections of standard, embedded, inverted, and suspended microstrip transmission lines are shown here. The physical characteristics of such a transmission line include microstrip width w, microstrip thickness t, dielectric thickness d, and relative permittivity constant ε.

Cross-section of standard, embedded, inverted, and suspended microstrip transmission lines

Stripline

Model transmission line as stripline transmission line. The cross-section of a stripline transmission line is shown in this figure. Its physical characteristics include strip width w, strip thickness t, dielectric thickness h, and relative permittivity constant ε.

Stripline transmission line

Two-wire

Model transmission line as two-wire transmission line. The cross-section of a two-wire transmission line is shown in the following figure. Its physical characteristics include the radius of wires a, separation or physical distance between the wire centers S, and relative permittivity and permeability of the wires.

Cross-section of a two-wire transmission line

Parallel plate

Model transmission line as a parallel-plate transmission line. The cross-section of a parallel-plate transmission line is shown in the following figure. Its physical characteristics include plate width w, and plate separation d. .

Cross-section of a parallel plate transmission line

Equation based

Model transmission line as an equation-based transmission line. The transmission line, which can be lossy or lossless, is treated as a two-port linear network.

Equation based transmission line

RLCG

Model transmission line as an RLCG transmission line. This line is defined in terms of its frequency-dependent resistance, inductance, capacitance, and conductance. The transmission line, which can be lossy or lossless, is treated as a two-port linear network.

Cross-section of RLGC transmission line

Delay in the transmission line, specified as a real scalar in s, ms, us, or ns.

To enable this parameter, choose one of the following:

  • Delay-based and lossless in Model type.

  • Delay-based and lossy in Model type.

Impedance of the transmission line, specified as a real scalar in Ohm, kOhm, MOhm, or GOhm.

Dependencies

To enable this parameter, choose one of the following:

  • Delay-based and lossless, Delay-based and lossy, or Equation-based in Model type.

  • Lumped parameter L-section or Lumped parameter Pi-section in Model type and By characterisitc impedance and capacitance in Parameterization.

Resistance per unit length of the transmission line, specified as a positive scalar in Ohm/m, kOhm/m, MOhm/m, or GOhm/m.

Dependencies

To enable this parameter, choose one of the following:

  • Delay-based and lossy or RLCG in Model type.

  • Lumped parameter L-section or Lumped parameter Pi-section in Model type and By characterisitc impedance and capacitance in Parameterization.

Number of segments in the transmission line, specified as a positive scalar.

Dependencies

To enable this parameter, choose one of the following:

  • Delay-based and lossy in Model type.

  • Lumped parameter L-section or Lumped parameter Pi-section in Model type and By characterisitc impedance and capacitance or By inductance and capacitance in Parameterization.

Type of parameters to model segments in transmission line, specified as By characterisitc impedance and capacitance or By inductance and capacitance.

Dependencies

To enable this parameter, select Lumped parameter L-section or Lumped parameter Pi-section in Model type.

Capacitance per unit length of the transmission line, specified as a positive scalar in F/m, mF/m, uF/m, nF/m, or pF/m.

Dependencies

To enable this parameter, choose Lumped parameter L-section, Lumped parameter Pi-section, or RLCG in Model type.

Conductance per unit length of the transmission line, specified as a positive scalar in S/m, mS/m, uS/m, or nS/m.

Dependencies

To enable this parameter, choose Lumped parameter L-section, Lumped parameter Pi-section, or RLCG in Model type.

Inductance per unit length of the transmission line, specified as a positive scalar in H/m, mH/m, uH/m, or nH/m.

Dependencies

To enable this parameter, choose one of the following:

  • Lumped parameter L-section, or Lumped parameter Pi-section in Model type and By inductance and capacitance in Parameterization.

  • RLCG in Model type

Outer radius of coaxial transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Coaxial in Model type.

Inner radius of coaxial transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Coaxial in Model type.

Physical width of the conductor, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Coplanar waveguide in Model type.

Physical width of the slot, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Coplanar waveguide in Model type.

Select this parameter to add an infinite-bottom conductor to your coplanar waveguide transmission line.

Dependencies

To enable this parameter, set Model type to Coplanar waveguide.

Type of microstrip transmission line, specified as Standard, Embedded, Inverted, or Suspended.

Dependencies

To enable this parameter, set Model type toMicrostrip .

Width of the microstrip transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, set Model type toMicrostrip.

Physical thickness of the conductor, specified as a nonnegative scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Coplanar waveguide or Microstrip in Model type.

Strip height of the inverted, suspended, or embedded microstrip transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Microstrip in Model type and choose Inverted, Suspended, or Embedded in Structure.

Radius of the conducting wires of the two-wire transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Two-wire in Model type.

Physical distance between the conducting wires of the two-wire transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Two-wire in Model type.

Width of the parallel-plate transmission line, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Parallel-plate in Model type.

Thickness of the dielectric separating the plates, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose Parallel-plate in Model type.

Propagation velocity of a uniform plane wave on the transmission line, specified as a positive scalar in meters per second

Dependencies

To enable this parameter, choose Equation-based in Model type.

Reduction in strength of the signal as it travels over the transmission line, specified as a positive scalar in meters per second

Dependencies

To enable this parameter, choose Equation-based in Model type.

Modeling frequencies, specified as a positive scalar or vector in Hz, kHz, MHz, or GHz.

Dependencies

To enable this parameter, choose Equation-based or RLCG in Model type.

Interpolation method used to calculate the values at the modeling frequencies, specified as Linear, Spline, or Cubic.

Dependencies

To enable this parameter, choose Equation-based or RLCG in Model type.

Conductivity of conductor, specified as a scalar in S/m, mS/m, uS/m, or nS/m.

Dependencies

To enable this parameter, choose Coaxial, Coplanar waveguide, Microstrip, Two-wire or Parallel-plate in Model type.

Thickness of the dielectric on which the conductor resides, specified as a positive scalar in m, cm, mm, um, in, or ft.

Default values of the dielectric thickness of coplanar waveguide, standard, embedded, inverted, and suspended microstrip transmission lines are listed in this table.

Model TypeStructureDefault Dielectric Thickness in mm
Coplanar waveguideN.A.0.635
MicrostripStandard and Inverted0.635
'Suspended'0.3175
'Embedded'1.37

Dependencies

To enable this parameter, set Model type to Microstrip or Coplanar waveguide.

Relative permeability of the dielectric, specified as a scalar.

Dependencies

To enable this parameter, set Model type to Coaxial, Two-wire, or Parallel-plate.

Relative permittivity of the dielectric, specified as a scalar.

Dependencies

To enable this parameter, set Model type to Coaxial, Coplanar waveguide, Microstrip, Two-wire, or Parallel-plate.

Loss tangent of the dielectric, specified as a scalar.

Dependencies

To enable this parameter, set Model type to Coaxial, Coplanar waveguide, Microstrip, Two-wire, or Parallel-plate.

Physical length of the transmission line or l, specified as a positive scalar in m, cm, mm, um, in, or ft.

Dependencies

To enable this parameter, choose one of the following:

  • Delay-based and lossy, Coaxial, Coplanar waveguide, Microstrip, or Two-wire, Parallel-plate, Equation-based, or RLCG in Model type.

  • Lumped parameter L-section or Lumped parameter Pi-section in Model type and By characterisitc impedance and capacitance or By inductance and capacitance in Parameterization.

Type of stub, specified as Not a stub, Shunt, or Series. See Parameter Calculations for Transmission Line with Stub.

Dependencies

To enable this parameter, choose Coaxial, Coplanar waveguide, Microstrip Two-wire, Parallel-plate, Equation-based, or RLCG in Model type.

Type of termination for stub, specified as Open or Short.

Dependencies

To enable this parameter, choose Series or Shunt in Stub mode.

Select this parameter to internally ground and hide the negative terminals. To expose the negative terminals, clear this parameter. By exposing these terminals, you can connect them to other parts of your model.

By default, this option is selected.

Modeling

Options to model S-parameters, specified as:

  • Frequency domain – Computes the baseband impulse response for each carrier frequency independently. This technique is based on convolution. There is an option to specify the duration of the impulse response. For more information, see Compare Time and Frequency Domain Simulation Options for S-parameters.

  • Time domain (rationalfit) – Computes the analytical rational model that approximates the whole range of the data.

For the Amplifier and S-parameters blocks, the default value is Time domain (rationalfit). For the Transmission Line block, the default value is Frequency domain.

Select Automatically estimate impulse response duration to calculate impulse response duration automatically. Clear the selection to specify impulse response duration.

Dependencies

To enable this parameter, choose Frequency domain in Modeling options.

Manually specify impulse response duration, specified as a positive scalar in s, ms, us, or ns.

Dependencies

To enable this parameter, clear Automatically estimate impulse response duration.

Fitting options for rationalfit, specified as Share all poles, Share poles by columns, or Fit individually.

For the Amplifier block, the default value is Fit individually. For the S-parameters block and Transmission Line block, the default value is Share all poles.

Dependencies

To enable this parameter, choose Time domain (rationalfit) in Modeling options.

Relative error acceptable in rationalfit output, specified as a real scalar in decibels.

Dependencies

To enable this parameter, choose Time domain (rationalfit) in Modeling options.

Shows values of Number of independent fits, Number of required poles, and Relative error achieved (dB).

When modeling using Time domain, the Plot in Visualization tab plots the data defined in Data Source and the values in the rationalfit function.

Dependencies

To enable this parameter, choose Time domain (rationalfit) in Modeling options.

Note

Modeling tab is enabled for all transmission line types except Delay-based and lossless, Delay-based and lossy, Lumped parameter L-section, and Lumped parameter pi-section.

More About

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Tips

  • In general, blocks that model delay effects rely on signal history. You can minimize numerical error that occur due to a lack of signal history at the start of a simulation. To do so, in the Configuration Parameters dialog box Solver pane you can specify an Initial step size. For models with delay-based Transmission Line blocks, use an initial step size that is less than the value of the Delay parameter.

References

[1] Sussman-Fort, S. E., and J. C. Hantgan. “SPICE Implementation of Lossy Transmission Line and Schottky Diode Models.” IEEE Transactions on Microwave Theory and Techniques.Vol. 36, No.1, January 1988.

[2] Pozar, David M. Microwave Engineering. Hoboken, NJ: John Wiley & Sons, Inc., 2005.

[3] Gupta, K. C., Ramesh Garg, Inder Bahl, and Prakash Bhartia. Microstrip Lines and Slotlines, 2nd Edition, Norwood, MA: Artech House, Inc., 1996.

[4] Ludwig, Reinhold and Pavel Bretchko. RF Circuit Design: Theory and Applications. Englewood Cliffs: NJ: Prentice-Hall, 2000.

[5] True, Kenneth M. “Data Transmission Lines and Their Characteristics.” National Semiconductor Application Note 806, April 1992.

Version History

Introduced in R2012a

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Behavior changed in R2022a