tdr

Characterize impedance discontinuities from S-parameters using TDR

Since R2025a

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    Description

    Use time-domain reflectometry (TDR) to characterize impedance discontinuities from S-parameter data.

    Creation

    Syntax

    tdrObj = tdr(sparam)
    tdrObj = tdr(sparam,Name=Value)

    Description

    tdrObj = tdr(sparam) creates a TDR object from a Touchstone file or an sparameters object specified in sparam to characterize impedance discontinuities in a system.

    tdrObj = tdr(sparam,Name=Value) sets properties using one or more name-value arguments. For example, t = tdr(ConvertToDifferential=true) enables differential S-parameter conversion.

    example

    Input Arguments

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    N-port S-parameters, specified as either an sparameters object or an N-port Touchstone data file.

    Properties

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    Port definitions for single-ended and differential ports, specified as a vector of integers.

    • Single-ended ports: Define on which ports to perform TDR analysis by specifying the port indices in the vector.

    • Differential ports: Define the differential ports pairs by specifying the port indices in a vector of the form [DiffPort1p, DiffPort1n, DiffPort2p, DiffPort2n ...].

    Example: [1 2]

    Option to enable differential S-parameter conversion, specified as a logical true (1) or false (0). Set this property to true or 1 to enable differential S-parameter conversion.

    Example: true

    Time step of the TDR step response, specified as a positive scalar in seconds. The object uses sample time to define a default input signal and a custom TDR stimulus waveform that you specify using the CustomWaveform property.

    Example: 10e-3

    Rise time of the TDR step stimulus waveform, specified as a positive scalar in seconds.

    Example: 10e-12

    Stop time of the TDR step response, specified as a positive scalar in seconds.

    Example: 10e-8

    Custom TDR stimulus waveform, specified as a 1-D vector. Use this property to generate a custom TDR stimulus as an alternative to the default stimulus generated by this object. By default, the stimulus generated by this object is a step response with the default sample time, rise time, and end time.

    Note

    You must specify sample time in the SampleTime property when creating a custom TDR stimulus waveform using the CustomWaveform property.

    Example: [zeros(1,16),ones(1,16),zeros(1,128)], pulse response assuming 16 samples per symbol.

    Rational fitting options to control the rational object properties, specified as a structure.

    This object uses a rational object to perform rational fitting on complex frequency-dependent data. To do this, the object uses a noniterative interpolatory algorithm to construct a fit with complex frequencies. Input the properties and name-value arguments of the rational object to the structure to control the aspect of the fit. For more information on how to set this property, see Plot Differential TDR Response of a Specific Differential Port Pair.

    Example: struct('Tolerance',-30,'MaxPoles',500)

    This property is read-only.

    Fit of each TDR response, returned as a vectors of rational objects.

    This property is read-only.

    TDR response in units of impedance, returned as a column matrix.

    This property is read-only.

    TDR response in units of volts, returned as a column matrix.

    This property is read-only.

    Time vector corresponding to the TDR responses, returned as a vector.

    This property is read-only.

    IEEE quality rating for causality, reciprocity, and passivity for the input S-parameters, returned as a structure.

    This property is read-only.

    Port label for each TDR response, returned as a string array.

    Example: ["Port 1" "Port 2" "Port 3" "Port 4"]

    Object Functions

    createTDRTableReturn TDR results as MATLAB table
    plotPlot TDR response
    tdr.automaticPortOrderingDisplay port ordering of S-parameter data
    tdr.sParamQualityReturn S-parameter quality metrics

    Examples

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    Open Live Script

    Create an S-parameter object from a 4-port Touchstone file. 

    sparam = sparameters('default.s4p');

    Create a TDR object and set the ConvertToDifferential property to true. In this example, the ports are not defined using the Ports property. Therefore, the tdr object automatically determines the differential ports. 

    tdrObj = tdr(sparam,'ConvertToDifferential',true);

    Plot the differential TDR response of a 4-port S-parameter. This plot displays the port mapping between single-ended (SE) ports that the object identified as differential (DD) pairs.

    plot(tdrObj)

    Figure contains an axes object. The axes object with title Differential TDR Response of sparam sparameter object, xlabel Time (ns), ylabel TDR (\Omega) contains 2 objects of type line. These objects represent DD Port 1: SE 1 & 3, DD Port 2: SE 2 & 4.

    Open Live Script

    Use a 16-port S-parameter Touchstone file to plot the TDR response of a differential port pair located at port 1 and 2.

    First, create a structure to define the rational fitting parameters. These parameters enable you to control the rational fitting process for complex S-parameters.

    rationalOptions = struct('Tolerance',-30,'MaxPoles',500);

    Create a TDR object with the differential port pair set to 1 and 2.

    tdrObj = tdr('default.s16p',...
    ConvertToDifferential=true, ...
    Ports=[1 2],...
    EndTime=9e-9,...
    RiseTime=10e-12,...
    SampleTime=5e-12, ...
    RationalOptions=rationalOptions);

    Plot the differential TDR response of the differential port pair 1 and 2.

    plot(tdrObj)

    Figure contains an axes object. The axes object with title Differential TDR Response of default.s16p, xlabel Time (ns), ylabel TDR (\Omega) contains an object of type line. This object represents DD Port 1: SE 1 & 2.

    Open Live Script

    Create a TDR object from a 4-port Touchstone file.

    tdrObj = tdr('default.s4p');

    Plot the single-ended TDR of a 4-port S-parameter in units of impedance.

    plot(tdrObj)

    Figure contains an axes object. The axes object with title Single Ended TDR Response of default.s4p, xlabel Time (ns), ylabel TDR (\Omega) contains 4 objects of type line. These objects represent Port 1, Port 2, Port 3, Port 4.

    Plot the single-ended TDR of a 4-port S-parameter in units of voltage.

    plot(tdrObj, Type="voltage", Title="TDR Response (Voltage)")

    Figure contains an axes object. The axes object with title TDR Response (Voltage), xlabel Time (ns), ylabel TDR (V) contains 4 objects of type line. These objects represent Port 1, Port 2, Port 3, Port 4.

    Plot the single-ended TDR of a 4-port S-parameter with respect to velocity of propagation of the medium. Scale the X-axis of this response in meters.

    plot(tdrObj,Vp=3e8/2,Title="TDR Response(m)")

    Figure contains an axes object. The axes object with title TDR Response(m), xlabel (m), ylabel TDR (\Omega) contains 4 objects of type line. These objects represent Port 1, Port 2, Port 3, Port 4.

    Create a TDR table that displays the time and voltage TDR values for all the ports specified in the TDR object.

    T = createTDRTable(tdrObj,tdrType='voltage')
    T=10000×5 table
    Time (s)    Port 1 (V)    Port 2 (V)    Port 3 (V)    Port 4 (V)
    ________    __________    __________    __________    __________

          0            1             1             1             1  
      1e-12       1.0062       0.99943        1.0126        1.0087  
      2e-12        1.012       0.99992        1.0237        1.0168  
      3e-12       1.0175        1.0013        1.0335        1.0243  
      4e-12       1.0228        1.0035        1.0421        1.0312  
      5e-12       1.0278        1.0063        1.0498        1.0376  
      6e-12       1.0324        1.0097        1.0565        1.0436  
      7e-12       1.0369        1.0135        1.0625        1.0491  
      8e-12        1.041        1.0175        1.0678        1.0541  
      9e-12       1.0449        1.0218        1.0726        1.0587  
      1e-11       1.0485        1.0263        1.0769         1.063  
    1.1e-11       1.0457        1.0313        1.0682        1.0582  
    1.2e-11        1.043        1.0353        1.0606        1.0536  
    1.3e-11       1.0404        1.0382        1.0542        1.0494  
    1.4e-11       1.0378        1.0402        1.0487        1.0453  
    1.5e-11       1.0353        1.0414         1.044        1.0415  
      ⋮

    Version History

    Introduced in R2025a

    See Also

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