Documentation

analyze

Analyze circuit object in frequency domain

Syntax

analyze(h,freq)
analyze(h,freq,zl,zs,zo,aperture)
analyze(h,freq,'condition1',value1,...,'conditionm',valuem)

Description

analyze(h,freq) calculates the following circuit 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

h is the handle of the circuit object to be analyzed. freq is a vector of frequencies, specified in hertz, at which to analyze the circuit. OIP3 is always infinite for passive circuits.

analyze(h,freq,zl,zs,zo,aperture) calculates the circuit data at the specified frequency values. The arguments zl, zs, zo, and aperture are optional. zl, zs, and zo represent the circuit load, circuit source, and reference impedances of the S-parameters, respectively. The default value of all these arguments is 50 ohms.

    Note:   When you specify impedance values, the analyze method changes the object's values to match your specification.

The aperture argument determines the two frequency points that the analyze method uses to compute the group delay for each frequency in freq. aperture can be a positive scalar or a vector of the same length of as freq.

    Note:   For rfckt.datafile, rfckt.passive, rfckt.amplifier, and rfckt.mixer objects that contain measured S-parameter data, the analyze method uses the two nearest measurement points to compute the group delay, regardless of the value of aperture.

Group delay τg at each frequency point f is the negative slope of the phase angle of S21 with respect to f:

τg(f)=ΔϕΔω=arg(S21(f+))arg(S21(f))2π(f+f)

where:

  • f+ is:

    • f(1 + aperture/2) for aperture < 1.

    • f + aperture/2 for aperture ≥ 1.

    If f is the maximum value of freq, then f+ = f.

  • f is:

    • f (1 – aperture/2) for aperture < 1.

    • f – aperture/2 for aperture ≥ 1.

    If f is the minimum value of freq, then f = f.

By default, analyze calculates the group delay in nanoseconds.

The value of aperture affects the accuracy of the computed group delay. If aperture is too large, the slope estimate may be not accurate. If aperture is too small, the computer numerical error may affect the accuracy of the group delay result.

analyze(h,freq,'condition1',value1,...,'conditionm',valuem) calculates the circuit data at the specified frequency values and operating conditions for the object h. The inputs 'condition1',value1,...,'conditionm',valuem are the condition/value pairs at which to analyze the object. Use this syntax for rfckt.amplifier, rfckt.mixer, and rfdata.data objects where the condition/value pairs are operating conditions from a .p2d or .s2d file.

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

When you analyze a network that contains several objects, RF Toolbox™ software does not issue an error or warning if the specified conditions cannot be applied to all objects. For some networks, because there is no error or warning, you can call the analyze method once to apply the same set of operating conditions to any objects where operating conditions are applicable. However, you may want to analyze a network that contains one or more of the following:

  • Several objects with different sets of operating conditions.

  • Several objects with the same set of operating conditions that are configured differently.

To analyze such a network, you should use the setop method to configure the operating conditions of each individual object before analyzing the network.

Analysis of Circuit Objects

For most circuit objects, the AnalyzedResult property is empty until the analyze method is applied to the circuit object. However, the following four circuit objects are the exception to this rule:

  • rfckt.datafile — By default, the AnalyzedResult property of rfckt.datafile objects contains the S-parameter, noise figure, and group delay values that are calculated over the network parameter frequencies in the passive.s2p data file. OIP3 is ∞ by default because the data in passive.s2p is passive.

  • rfckt.passive — By default, the AnalyzedResult property of rfckt.passive objects contains the S-parameter, noise figure, and group delay values that are the result of analyzing the values stored in the passive.s2p file at the frequencies stored in this file. These frequency values are also stored in the NetworkData property. OIP3 is always ∞ for rfckt.passive objects because the data is passive.

  • rfckt.amplifier — By default, the AnalyzedResult property of rfckt.amplifier objects contains the S-parameter, noise figure, OIP3, and group delay values that result from analyzing the values stored in the default.amp file at the frequencies stored in this file. These frequency values are also stored in the NetworkData property.

  • rfckt.mixer — By default, the AnalyzedResult property of rfckt.mixer objects contains the S-parameter, noise figure, OIP3, and group delay values that result from analyzing the values stored in the default.s2p file at the frequencies stored in this file. These frequency values are also stored in the NetworkData property.

For a detailed explanation of how the analyze method calculates the network parameters, noise figure values, and OIP3 values for a particular object, see the AnalyzedResult property on the reference page for that object.

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