Table Of Contents

MT Measure MSK Quadrature Impairments (G Dataflow)

Last Modified: January 9, 2017

Calculates minimum-shift keying (MSK) quadrature impairments on a point-by-point basis on the oversampled waveform.

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recovered complex waveform

The time-aligned and oversampled complex waveform data after matched filtering, frequency offset correction, and phase offset correction. Wire the recovered complex waveform parameter of MT Demodulate MSK to this parameter.

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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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detected complex waveform

The ideal oversampled waveform. Wire the detected complex waveform parameter of MT Demodulate MSK to this parameter.

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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 ideal oversampled waveform as a complex-valued array.

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impairment measurement window

The window over which impairments are measured.

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start index

Index of the first sample of the measurement window.

Default: 0

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width

Number of symbols over which to measure impairments. A value of -1 (default) measures impairments over all symbols. Positive values must be two or greater.

Default: -1

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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.

Default: no error

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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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quadrature skew

The measured quadrature skew of the complex waveform in degrees.

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samples per symbol

Number of samples per symbol in the modulated complex waveform.

Default: 16

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magnitude error

The measured magnitude error as a percentage. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

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RMS measurement

The RMS impairment value calculated over the impairment measurement window.

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peak measurement

The peak impairment value measured over the impairment measurement window.

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peak symbol index

Index of the symbol having the peak magnitude of impairment.

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individual symbol measurements

The impairment value for each individual symbol.

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DC offset measurements

The measured DC offset of the I or Q waveforms as a percentage of the largest I and Q value in the symbol map of the recovered complex waveform.

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I

The DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.

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Q

The DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.

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origin offset

The offset, in dB, of the constellation origin from its ideal location.

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IQ gain imbalance

The measured ratio of I gain to Q gain, in dB.

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phase error

The measured phase error in degrees. Notice that the phase offset is removed by the demodulator and is excluded from this measurement.

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RMS measurement

The RMS impairment value calculated over the impairment measurement window.

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peak measurement

The peak impairment value measured over the impairment measurement window.

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peak symbol index

Index of the symbol having the peak magnitude of impairment.

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individual symbol measurements

The impairment value for each individual symbol.

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EVM

The measured error vector magnitude (EVM) expressed as a percentage.

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RMS measurement

The RMS impairment value calculated over the impairment measurement window.

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peak measurement

The peak impairment value measured over the impairment measurement window.

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peak symbol index

Index of the symbol having the peak magnitude of impairment.

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individual symbol measurements

The impairment value for each individual symbol.

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modulation error ratio

The measured modulation error ratio in dB.

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error out

Error information. The node produces this output according to standard error behavior.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported


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