rfckt.rlcgline

Passive component or network

Description

Use the rlcgline object to represent RLCG transmission lines that are characterized by line loss, line length, stub type, and termination.

Creation

Syntax

h = rfckt.rlcgline

h = rfckt.rlcgline('Property1',value1,'Property2',value2,...)

Description

h = rfckt.rlcgline returns an RLCG transmission line object whose properties are set to their default values.

h = rfckt.rlcgline('Property1',value1,'Property2',value2,...) sets properties using one or more name-value pairs. You can specify multiple name-value pairs. Enclose each property name in a quote

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. Analyzed Result is a read-only property. For more information refer, .Algorithms.

Data Types: function_handle

R — Resistance values per length

vector

Resistance values per length, specified as a vector in ohms per meter. The resistance values correspond to the frequency values in 'Freq' property. All values must be positive. The default value is 0.

Data Types: double

C — Capacitance values per length

vector

Capacitance values per length, specified as a vector in farads per meter. The capacitance values correspond to the frequency values in 'Freq' property. All values must be positive. The default value is 0.

Data Types: double

Freq — Frequency data

M-element vector

Frequency data for the RLCG values, specified as a M-element vector. The values must be positive and correspond to the order of the RLCG values. The default value is 1e9.

Data Types: double

G — Conductance values per length

vector

Conductance values per length, specified as a vector in Siemens per meter. The conductance values correspond to the frequency values in 'Freq' property. All values must be positive. The default value is 0.

Data Types: double

IntpType — Interpolation method used in rfckt.rlcgline

'Linear' (default) | 'Spline' | 'Cubic'

Interpolation method used in rfckt.rlcgline, specified as one of the following values:

Method	Description
Linear	Linear interpolation
Spline	Cubic spline interpolation
Cubic	Piecewise cubic Hermite interpolation

Data Types: char

L — Inductance values per length

vector

Inductance values per length, specified as vector in henries per meter. The inductance values correspond to the frequency values in 'Freq' property. All values must be positive. The default value is 0.

Data Types: double

LineLength — Physical length of transmission line

scalar

Physical length of transmission line, specified as a scalar in meters. The default value is 0.01.

Data Types: double

Name — Object name

'RLCG Transmission Line' (default) | 1-by-N character array

Object name, specified as a 1-by-N character array. Name is a read-only property.

Data Types: char

nport — Number of ports

positive integer

Number of ports, specified as a positive integer. nportt is a read-only property. The default value is 2.

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

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 specified circuit object parameters on X-Y plane
plotyy	Plot specified parameters on X-Y plane with Y-axes on both left and right sides
getop	Display operating conditions
polar	Plot specified object parameters on polar coordinates
semilogx	Plot specified circuit object parameters using log scale for x-axis
semilogy	Plot specified circuit object parameters using log scale for y-axis
smith	Plot specified circuit object parameters on Smith chart
write	Write RF data from circuit or data object to file
getz0	Get characteristic impedance of 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

RLCG Transmission Line

Create an RLCG transmission line using rfckt.rlcgline.

rlcgtx=rfckt.rlcgline('R',0.002,'C',8.8542e-12,'L',1.2566e-6,'G',0.002')

rlcgtx = 
   rfckt.rlcgline with properties:

              Freq: 1.0000e+09
                 R: 0.0020
                 L: 1.2566e-06
                 C: 8.8542e-12
                 G: 0.0020
          IntpType: 'Linear'
        LineLength: 0.0100
          StubMode: 'NotAStub'
       Termination: 'NotApplicable'
             nPort: 2
    AnalyzedResult: []
              Name: 'RLCG Transmission Line'

Algorithms

The analyze method treats the transmission line, which can be lossy or lossless, as a 2-port linear network. It uses the interpolation method you specify in the IntpType property to find the R, L, C, and G values at the frequencies you specify when you call analyze. Then, it calculates the characteristic impedance, Z0, phase velocity, PV, and loss using these interpolated values. It computes the AnalyzedResult property of a stub or as a stubless line using the data stored in the rfckt.rlcgline 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 resistance (R), inductance (L), conductance (G), and capacitance (C) per unit length (meters) as follows:

  $$\begin{array}{c}{Z}_0=\sqrt{\frac{R+j2\pi fL}{G+j2\pi fC}}\\ k=k_r+j{k}_i=\sqrt{(R+j2\pi fL)(G+j2\pi FC)}\end{array}$$

• 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 as shown in the following figure.

  

  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 as shown in the following figure.

  

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

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

The analyze method uses the S-parameters to calculate the group delay values at the frequencies specified in the analyze input argument freq, as described in the analyze reference page.

References

[1] Ludwig, R. and P. Bretchko, RF Circuit Design: Theory and Applications, Prentice-Hall, 2000