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Plot specified circuit object parameters using log-log scale


lineseries = loglog(h,parameter) plots the specified parameter in the default format using a log-log scale. h is the handle of a circuit ( rfckt ) object.

The loglog method returns a column vector of handles to lineseries objects, one handle per line. This output is the same as the output returned by the MATLAB® loglog method.


lineseries = loglog(h,parameter1,...,parametern) plots the parameters parameter1, ..., parametern from the object h on an X-Y plane using logarithmic scales for both the x- and y- axes.

lineseries = loglog(h,parameter1,...,parametern,format) plots the parameters parameter1, ..., parametern in the specified format. format is the format of the data to be plotted, e.g. 'Magnitude (decibels)'.


For all circuit objects except those that contain data from a data file, you must perform a frequency domain analysis with the analyze method before calling loglog.

lineseries=loglog(h,'parameter1',...,'parametern', format,xparameter ,xformat,'condition1',value1,..., 'conditionm',valuem,'freq',freq,'pin',pin) plots the specified parameters at the specified operating conditions for the object h.


If h has multiple operating conditions, such as from a .p2d or .s2d file, the loglog method operates as follows:

  • If you do not specify any operating conditions as arguments to the loglog method, then the method plots the parameter values based on the currently selected operating condition.

  • If you specify one or more operating conditions, the loglog method plots the parameter values based on those operating conditions.

  • When you use an operating condition for the xparameter input argument, the method plots the parameters for all operating condition values.


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Create and analyze a two-wire network object.

 tx1 = rfckt.twowire('Radius',7.5e-4);
 freq = linspace(1e9,10e9,10);
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'

Plot S11 using the log-log scale.

 linesereis = loglog(tx1,'S11')

linesereis = 
  Line (S_{11}) with properties:

              Color: [0 0.4470 0.7410]
          LineStyle: '-'
          LineWidth: 0.5000
             Marker: 'none'
         MarkerSize: 6
    MarkerFaceColor: 'none'
              XData: [1 2 3 4 5 6 7 8 9 10]
              YData: [1x10 double]
              ZData: [1x0 double]

  Show all properties

Input Arguments

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RF circuit or data object, specified as object handle.

Data Types: char | string

Valid parameters of circuit objects, specified as a character vector or string.

Type listparam(rfobject) to get a list of valid parameters for a circuit object, h. Type listformat(rfobject,parameter) to see the legitimate formats for a specified parameter. The first listed format is the default for the specified parameter.

independent variable to use in plotting the specified parameters. Several xparameter values are available for all objects. When you import rfckt.amplifier, rfckt.mixer, or object specifications from a .p2d or .s2d file, you can also specify any operating conditions from the file that have numeric values, such as bias.

This table shows the commonly available parameters and the corresponding xparameter values. The default values listed in the table are used if the xparameter is not specified.

Parameter Namexparameter values
Pout, Phase, LS11, LS12, LS21, LS22Pin (default), Freq
S11, S12, S21, S22, NF, IIP3, OIP3, GroupDelay, VSWRIn, VSWROut, GammaIn, GammaOut, FMIN, GammaOPT, RN, TF1, TF2, Gt, Ga, Gp, Gmag, Gmsg, GammaMS, GammaML, K, Delta, Mu, MuPrimeFreq

Format for the specified xparameter. You do not need to specify xformat when xparameter is an operating condition.

This table shows the available xformat values that are available for the xparameter values, along with the default values that are used if xformat is not specified.

xparameter valuesxformat values
PindBm (default), mW, W, dBW

THz, GHz, MHz, KHz, Hz

By default, xformat is chosen to provide the best scaling for the given xparameter values.

AMMagnitude (decibels) (default), Magnitude (linear)

Name-Value Pair Arguments

Example: semilogy(h,'Pout','Pin','Freq',2.1e9)

Specify optional comma-separated pairs of Name,Value pair arguments. Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (''). You can specify several name and value pair arguments in any order as Name1, Value1, ..., NameN, ValueN.

'condition1',value1, ..., conditionm,valuem are the optional condition/value pairs at which to plot the specified parameters. These pairs are usually operating conditions from a .p2d or .s2d file. For some parameters, you can specify a set of frequency or input power values at which to plot the specified parameter.

For example:

  • When plotting large-signal S-parameters as a function of input power, you can specify frequency points of interest using condition/value pairs.

  • When plotting large-signal S-parameters as a function of frequency, you can specify input power levels of interest using condition/value pairs.

  • When plotting parameters as a function of an operating condition, you can specify both frequency and input power values using condition/value pairs.

Frequency in Hz, specified as the comma-separated pair consisting of 'Freq' and a positive scalar.

Input power level, in dBm, specified as the comma-separated pair consisting of 'Pin' and a positive scalar.

Output Arguments

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lineseries object, returned as a column vector of object handles.


  • Use the Property Editor ( propertyeditor ) or the MATLAB set function to change Line Properties. The reference pages for MATLAB functions such as figure, axes, and text also list available properties and provide links to more complete property descriptions.


    Use the MATLAB loglog function to create a log-log scale plot of parameters that are specified as vector data and are not part of a circuit ( rfckt ) object or data ( rfdata ) object.

Introduced in R2007a