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Analyze RFCKT object in frequency domain



analyze(rfcktobject,frequency) calculates the following rfckt data at the specified frequency values:

  • Circuit network parameters

  • Noise figure

  • Output third-order intercept point

  • Power data

  • Phase noise

  • Voltage standing-wave ratio

  • Power gain

  • Group delay

  • Reflection coefficients

  • Stability data

  • Transfer function


rfbudget and RF Budget Analyzer is recommend over analyze because they enable you to analyze gain, noise figure, IP2, and IP3 of cascaded RF elements and export to RF Blockset™ and rfsystem for circuit envelope analysis. (since R2023b)

analyze(rfcktobject,frequency,zl,zs,zo,aperture) calculates the circuit data specified frequency values with optional arguments such as load impedance, source impedance, reference impedance and aperture.

analyze(rfcktobject,frequency,condition,value) calculates the circuit data at the specified frequency values and operating conditions for the circuitdata object. For more information to set conditions and values, see setop function.


When you specify condition/value pairs, the analyze method changes the object's values to match your specification.


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Create and analyze a two-wire network object.

ans = 
   rfckt.twowire with properties:

            Radius: 7.5000e-04
        Separation: 0.0016
               MuR: 1
          EpsilonR: 2.3000
       LossTangent: 0
         SigmaCond: Inf
        LineLength: 0.0100
          StubMode: 'NotAStub'
       Termination: 'NotApplicable'
             nPort: 2
    AnalyzedResult: [1x1]
              Name: 'Two-Wire Transmission Line'

This example shows how to analyze an RF amplifier at different reference impedances.

Assign the load and the source impedances.

zl = 50 - 50*1i;
zs = 200 + 50*1i;

Create two amplifier circuits with the same Touchstone® file.

circuit50 = read(rfckt.amplifier,'default.s2p');
circuit75 = read(rfckt.amplifier,'default.s2p');

Analyze the amplifier circuits at two different reference impedance, 50 and 75 ohms.

analyzed_circuit50 = analyze(circuit50, circuit50.NetworkData.Freq, zl, zs,50);
analyzed_circuit75 = analyze(circuit75, circuit50.NetworkData.Freq, zl, zs,75);

Plot S21 for the two amplifier circuits.

hold on;

Note that in this example two amplifier circuits derived from a same touchstone file at two different reference impedances produce two different S21 plot. This is because, the S-parameters are only dependent on the reference impedance, z0, and not on the source impedance, zs or the load impedance, zl.

The analyze function stores zs and zl in the amplifier and these impedances are used when a zs and zl dependent parameter is calculated. For example, plot transducer gain, Gt of the two amplifier circuits.

hold on;

Note that Gt is dependent on zs, zl, and z0. Hence for the two amplifier circuits derived from a same touchstone file with same zs and zl at z0 of 50 and 75 ohms yields the same Gt.

Input Arguments

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RFCKT object to analyze, specified as a object handle.

Example: amp = rfckt.amplifier;analyze(amp,frequency)Analyzes the rfckt.amplifier object with handle amp at the specified frequency.

Data Types: char | string

Simulation frequencies, specified as a vector in hertz.

Example: 1.9e9

Data Types: double

Load impedance, specified as a scalar in ohms.

Example: 40

Data Types: double

Source impedance, specified as a scalar in ohms.

Example: 40

Data Types: double

Reference impedance of S-parameters, specified as a real positive scalar or real positive vector in ohms. The length of this vector must be same as of frequency argument.

Example: 40

Data Types: double

Value to determine two closely spaced frequencies at each simulation frequency for the calculation of group delay, specified as a positive scalar or a vector of same length as simulation frequencies. If the aperture is not specified, it will be determines based on the simulation frequencies.

Example: 40

Data Types: double

Version History

Introduced before R2006a