Table Of Contents

MT Apply IQ Impairments (G Dataflow)

Version:
    Last Modified: February 7, 2018

    Applies various I/Q impairments to the complex baseband modulated waveform.

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    input complex waveform

    The modulated complex baseband waveform data.

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    t0

    Trigger (start) time of the Y array.

    Default: 0.0

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    dt

    Time interval between data points in the Y array.

    Default: 1.0

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    Y

    The complex-valued signal-only baseband modulated waveform. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

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    q dc offset

    The desired DC offset of the Q waveform as a percentage of the input complex waveform. Valid values are -100 to +100, inclusive.

    Default: 0

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    iq gain imbalance

    The desired ratio of I gain to Q gain, in dB. Valid values are between -6.0 and +6.0.

    Default: 0

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    quadrature skew

    The desired quadrature skew of the complex waveform in degrees. Valid values are between -30.0 and +30.0 degrees.

    Default: 0

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    i dc offset

    The desired DC offset of the I waveform as a percentage of full scale of the input complex waveform. Valid values are between -100 and +100.

    Default: 0.0

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    impairment definition

    A value that indicates which set of equations is used to represent impairments.

    In the equations in the following table, I is the real component and Q is the imaginary component of each sample in the input complex waveform. I and Q are the real and imaginary components of the corresponding sample in the output complex waveform. I is I DC Offset (%) / 100, and Q is Q DC Offset (%) / 100.

    Name Description
    Vertical Shear

    The definition uses the following equations for I/Q impairments:

    I = a * I + I

    Q = a * sin ( φ ) * I + b * cos ( φ ) * Q + Q

    where

    φ is the specified quadrature skew, in radians

    γ = 10(IQ gain imbalance/20)

    a = γ * b

    b = 2 1 + γ 2

    In matrix form, these equations are represented by

    [ I Q ] = S [ I Q ] + [ I Q ]

    where

    S = [ a 0 a * sin φ b * cos φ ]

    Axis Shear

    With this option selected, this node uses an impairment definition that simplifies the conversion between measured impairments and their inverse impairments. For example, you may want to measure the I/Q impairments of a system and compensate for those impairments by applying the inverse impairments to the generated or received waveform. Using the Axis Shear definition, given a measured skew and imbalance (in dB), the inverse impairments are -1.0 * skew and -1.0 * imbalance. This definition uses the following equations for IQ impairments:

    I = I * γ Q * ( φ 2 ) + I

    Q = I * ( φ 2 ) + Q * ( 1 γ ) + Q

    where

    γ = 10(IQ gain imbalance/20)

    φ is the specified quadrature skew, in radians

    In matrix form, these equations are represented by

    [ I Q ] = S [ I Q ] + [ I Q ]

    where

    S = [ γ φ / 2 φ / 2 1 γ ]

    Default: Vertical Shear

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    frequency offset

    The desired frequency offset, in Hertz (Hz), to apply to the output complex waveform.

    Default: 0

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    reset?

    A Boolean that determines whether this node continues applying the impairments using the previous iteration states.

    TRUE Restarts the impairment generation process.
    FALSE Continues applying the impairments using the previous iteration states.

    Default: TRUE

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    output complex waveform

    The impaired complex baseband modulated waveform data returned by this node.

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    t0

    Trigger (start) time of the Y array.

    Default: 0

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    dt

    Time interval between data values in the Y array.

    Default: 1.0

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    Y

    The complex-valued signal-only baseband modulated waveform. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

    Web Server: Not supported in VIs that run in a web application


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