rfckt.microstrip

Microstrip transmission line

Description

Use the rfckt.microstrip object to create a microstrip transmission lines characterized by line dimensions and optional stub properties.

A microstrip transmission line is shown in cross-section in the following figure. Its physical characteristics include the microstrip width (w), the microstrip thickness (t), the substrate height (d), and the relative permittivity constant (ε).

Note

txlineMicrostrip is recommended over rfckt.microstrip because it enables you to:

• Create a standard, embedded, inverted, or suspended microstrip transmission line.

• Build a circuit object with a standard, embedded, inverted, or suspended microstrip transmission line.

• Input the txlineMicrostrip object to the microstripLine object from RF PCB Toolbox™ for EM modeling.

• Model a standard, embedded, inverted, or suspended microstrip transmission line element in an RF chain created using an rfbudget object or the RF Budget Analyzer app, and then export this element to RF Blockset™ or to rfsystem System object™ for circuit envelope analysis.

(since R2023b)

Creation

Syntax

h = rfckt.microstrip

h = rfckt.microstrip(Name,Value)

Description

h = rfckt.microstrip returns a microstrip transmission line object whose properties are set to their default values.

h = rfckt.microstrip(Name,Value) sets properties using one or more name-value pairs. For example, rfckt.microstrip('Thickness',0.0075e-6) creates a microstrip transmission line with thickness of 0.0075e-6 meters. You can specify multiple name-value pairs. Enclose each property name in a quote. Properties not specified retain their default values.

Properties

AnalyzedResult — Computed S-parameters, noise figure, OIP3, and group delay values

rfdata.data object

Computed S-parameters, noise figure, OIP3, and group delay values, specified as rfdata.data object. AnalyzedResult is a read-only property. For more information refer, Algorithms.

Data Types: function_handle

EpsilonR — Relative permittivity of dielectric

9.8 (default) | scalar

Relative permittivity of dielectric, specified as a scalar. The relative permittivity is the ratio of permittivity of the dielectric,$$\epsilon$$, to the permittivity in free space, $${\epsilon }_0$$.

Data Types: double

Height — Dielectric thickness or physical height of conductor

6.35e-4 (default) | scalar

Dielectric thickness or physical height of the conductor, specified as a scalar in meters.

Data Types: double

LineLength — Physical length of transmission

0.01 (default) | scalar

Physical length of transmission, specified as a scalar in meters.

Data Types: double

LossTangent — Loss angle tangent of dielectric

0 (default) | scalar

Loss angle tangent of dielectric, specified as a scalar.

Data Types: double

Name — Object name

Read-only: 'Microstrip Transmission Line' (default) | 1-by-N character array | string scalar

This property is read-only.

Object name, specified as an 1-by-N character array or string scalar.

Data Types: char

nport — Number of ports

2 (default) | positive integer

Number of ports, specified as a positive integer. nportt is a read-only property.

Data Types: double

SigmaCond — Conductor conductivity

Inf (default) | scalar

Conductor conductivity, specified as a scalar in Siemens per meter (S/m).

Data Types: double

StubMode — Type of stub

'NotaStub' (default) | 'Series' | 'Shunt'

Type of stub, specified as one of the following values: 'NotaStub', 'Series', 'Shunt'.

Data Types: double

Termination — Stub transmission line termination

'NotApplicable' (default) | 'Open' | 'Short'

Stub transmission line termination, specified as one of the following values: 'NotApplicable', 'Open', 'Short'.

Data Types: double

Thickness — Physical thickness of microstrip

5.0e-6 (default) | scalar

Physical thickness of microstrip, specified as a scalar in meters.

Data Types: double

Width — Physical width of parallel-plate

6.0e-4 (default) | scalar

Physical width of parallel-plate, specified as a scalar in meters.

Data Types: double

Object Functions

analyze	Analyze RFCKT object in frequency domain
calculate	Calculate specified parameters for rfckt objects or rfdata objects
circle	Draw circles on Smith Chart
extract	Extract specified network parameters from rfckt object or data object
listformat	List valid formats for specified circuit object parameter
listparam	List valid parameters for specified circuit object
loglog	Plot specified circuit object parameters using log-log scale
plot	Plot circuit object parameters on X-Y plane
plotyy	Plot parameters of RF circuit or RF data on xy-plane with two Y-axes
getop	Display operating conditions
polar	Plot specified object parameters on polar coordinates
semilogx	Plot RF circuit object parameters using log scale for x-axis
semilogy	Plot RF circuit object parameters using log scale for y-axis
smith	Plot circuit object parameters on Smith Chart
write	Write RF data from circuit or data object to file
getz0	Calculate characteristic impedance of RFCKT transmission line object
read	Read RF data from file to new or existing circuit or data object
restore	Restore data to original frequencies
getop	Display operating conditions
groupdelay	Group delay of S-parameter object or RF filter object or RF Toolbox circuit object

Examples

Microstrip Transmission Line

Create a microstrip transmission line using rfckt.microstrip.

tx1=rfckt.microstrip('Thickness',0.0075e-6)

tx1 = 
   rfckt.microstrip with properties:

             Width: 6.0000e-04
            Height: 6.3500e-04
         Thickness: 7.5000e-09
          EpsilonR: 9.8000
       LossTangent: 0
         SigmaCond: Inf
        LineLength: 0.0100
          StubMode: 'NotAStub'
       Termination: 'NotApplicable'
             nPort: 2
    AnalyzedResult: []
              Name: 'Microstrip Transmission Line'

Algorithms

The analyze method treats the microstrip line as a 2-port linear network and models the line as a transmission line with optional stubs. The analyze method computes the AnalyzedResult property of the transmission line using the data stored in the rfckt.microstrip object properties as follows:

• If you model the transmission line as a stubless line, the analyze method first calculates the ABCD-parameters at each frequency contained in the modeling frequencies vector. It then uses the abcd2s function to convert the ABCD-parameters to S-parameters.

  The analyze method calculates the ABCD-parameters using the physical length of the transmission line, d, and the complex propagation constant, k, using the following equations:

  $$\begin{array}{l}A=\frac{e^{kd}+e^{-kd}}{2}\\ B=\frac{Z_0*\left(e^{kd}-e^{-kd}\right)}{2}\\ C=\frac{e^{kd}-e^{-kd}}{2*Z_0}\\ D=\frac{e^{kd}+e^{-kd}}{2}\end{array}$$

  Z₀ and k are vectors whose elements correspond to the elements of f, the vector of frequencies specified in the analyze input argument freq. Both can be expressed in terms of the specified conductor strip width, substrate height, conductor strip thickness, relative permittivity constant, conductivity, and dielectric loss tangent of the microstrip line, as described in [1].

• If you model the transmission line as a shunt or series stub, the analyze method first calculates the ABCD-parameters at the specified frequencies. It then uses the abcd2s function to convert the ABCD-parameters to S-parameters.

  When you set the StubMode property to 'Shunt', the 2-port network consists of a stub transmission line that you can terminate with either a short circuit or an open circuit.

  

  Z_in is the input impedance of the shunt circuit. The ABCD-parameters for the shunt stub are calculated as:

  $$\begin{array}{c}A=1\\ B=0\\ C=1/Z_{in}\\ D=1\end{array}$$

  When you set the StubMode property to 'Series', the 2-port network consists of a series transmission line that you can terminate with either a short circuit or an open circuit.

  

  Z_in is the input impedance of the series circuit. The ABCD-parameters for the series stub are calculated as:

  $$\begin{array}{c}A=1\\ B=Z_{in}\\ C=0\\ D=1\end{array}$$

References

[1] Gupta, K. C., R. Garg, I. Bahl, and P. Bhartia, Microstrip Lines and Slotlines, 2nd Edition, Artech House, Inc., Norwood, MA, 1996.

Version History

Introduced before R2006a