AnalyzedResult property - Class: rfckt.cascade
Package: rfckt

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

Values

rfdata.data object

Description

Handle to an rfdata.data object that contains the S-parameters, noise figure, OIP3, and group delay values computed over the specified frequency range using the analyze method. This property is empty by default.

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.

  

  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 C_A' and C_A", corresponding to the first two matrices in the cascade, using the following equation:

  

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

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

  

  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:

  

  In the two preceding equations, Z_S 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:

  

  where G_n is the gain of the nth element of the cascade and OIP_3,N is the OIP₃ of the n^th 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.

Examples

Analyze a cascade of three circuit objects:

amp = rfckt.amplifier('IntpType','cubic');
tx1 = rfckt.txline;
tx2 = rfckt.txline;
casc = rfckt.cascade('Ckts',{tx1,amp,tx2});
analyze(casc,[1e9:1e7:2e9]);
casc.AnalyzedResult

References

Hillbrand, H. and P.H. Russer, "An Efficient Method for Computer Aided Noise Analysis of Linear Amplifier Networks," IEEE Transactions on Circuits and Systems, Vol. CAS-23, Number 4, pp. 235–238, 1976.

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