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rfckt.cascade

Cascaded network

Description

Use the cascade object to represent cascaded networks of RF objects that are characterized by the components that make up the individual network. The following figure shows the configuration of a pair of cascaded networks.

Creation

Syntax

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

Description

example

h = rfckt.cascade returns a cascaded network object whose properties all have their default values.

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

sets properties using one or more name-value pairs. For example, rfckt.cascade ('nport',2)creates a 2-port RF cascade network. You can specify multiple name-value pairs. Enclose each property naem in a quote.

Properties

expand all

This property is read-only.

Computed S-parameters, noise figure, OIP3, and group delay values. For more information refer, Algorithms.

Data Types: function_handle

Circuit objects in network. All circuits must be 2-port. By default, this property is empty.

Data Types: char

This property is read-only.

Name of cascaded network.

Data Types: char

This property is read-only.

Number of ports of cascaded network. The default value is 2.

Data Types: double

Object Functions

analyzeAnalyze circuit object in frequency domain
calculateCalculate specified parameters for circuit object
circleDraw circles on Smith chart
listformatList valid formats for specified circuit object parameter
listparamList valid parameters for specified circuit object
loglogPlot specified circuit object parameters using log-log scale
plotPlot specified circuit object parameters on X-Y plane
plotyyPlot specified object parameters with y-axes on both left and right sides
polarPlot specified circuit object parameters on polar coordinates
semilogxPlot specified circuit object parameters using log scale for x-axis
semilogyPlot specified circuit object parameters using log scale for y-axis
smithPlot specified circuit object parameters on Smith chart
writeWrite RF data from circuit or data object to file

Examples

expand all

Create a cascade network using rfckt.cascade with amplifier and transmission lines as elements.

amp = rfckt.amplifier('IntpType','cubic');
tx1 = rfckt.txline;
tx2 = rfckt.txline;
casccircuit = rfckt.cascade('Ckts',{tx1,amp,tx2})
casccircuit = 

   rfckt.cascade with properties:

              Ckts: {1x3 cell}
             nPort: 2
    AnalyzedResult: []
              Name: 'Cascaded Network'

Algorithms

The analyze method computes the AnalyzedResult property using the data stored in the Ckts property as follows:

  • The analyze method starts calculating the ABCD-parameters of the cascaded network by converting each component network's parameters to an ABCD-parameters matrix. The figure shows a cascaded network consisting of two 2-port networks, each represented by its ABCD matrix.

    The analyze method then calculates the ABCD-parameter matrix for the cascaded network by calculating the product of the ABCD matrices of the individual networks.

    The following figure shows a cascaded network consisting of two 2-port networks, each represented by its ABCD-parameters.

    The following equation illustrates calculations of the ABCD-parameters for two 2-port networks.

    [ABCD]=[ABCD][ABCD]

    Finally, analyze converts the ABCD-parameters of the cascaded network to S-parameters at the frequencies specified in the analyze input argument freq.

  • The analyze method calculates the noise figure for an N-element cascade. First, the method calculates noise correlation matrices CA' and CA, corresponding to the first two matrices in the cascade, using the following equation:

    CA=2kT[RnNFmin12RnYoptNFmin12RnYoptRn|Yopt|2]

    where k is Boltzmann's constant, and T is the noise temperature in Kelvin.

    The method combines CA' and CA into a single correlation matrix CA using the equation

    CA=CA'+[A'B'C'D']CA''[A'B'C'D']

    By applying this equation recursively, the method obtains a noise correlation matrix for the entire cascade. The method then calculates the noise factor, F, from the noise correlation matrix of as follows:

    F=1+z+CAz2kTRe{ZS}z=[1ZS*]

    In the two preceding equations, ZS is the nominal impedance, which is 50 ohms, and z+ is the Hermitian conjugation of z.

  • The analyze method calculates the output power at the third-order intercept point (OIP3) for an N-element cascade using the following equation:

    OIP3=11OIP3,N+1GNOIP3,N1++1GNGN1G2OIP3,1

    where Gn is the gain of the nth element of the cascade and OIP3,N is the OIP3 of the nth element.

  • The analyze method uses the cascaded 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.

Introduced before R2006a

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