MT Measure Quadrature Impairments VI

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MT Measure Quadrature Impairments VI

Measures and reports quadrature impairments over a single user-specified window for each of the supported modulation types. This VI must be called once for each measurement window.

Use the pull-down menu to select an instance of this VI.

Details

MT Measure PSK Quadrature Impairments

This polymorphic instance calculates and reports PSK quadrature impairments on a symbol-by-symbol basis at the symbol timing.

MT Measure PSK Quadrature Impairments

PSK system parameters specifies parameter values defining the PSK system. Wire the PSK system parameters cluster from the PSK (M) or PSK (Map) instance of the MT Generate System Parameters VI to this cluster. Do not alter the values.

samples per symbol specifies an even, positive number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate. The default is 16.

symbol map specifies an ordered array that maps each Boolean symbol to its desired coordinates in the complex plane. The number of states in the array must be 2^N, where N is the number of bits per symbol.

differential PSK specifies how the PSK modulation represents symbols. Differential operation is used to implement PSK formats such as differential quadrature PSK (DQPSK) and /4-DQPSK.

disable (0)	Symbols are represented as constellation points. This is the default value.
enable (1)	Symbols are represented as the transitions between constellation points.

PSK type specifies the type of PSK modulation.

normal	Sets the modulation type to regular PSK. This is the default value.
shifted	Rotates the constellation by /M each symbol.
offset	Sets the modulation type to offset quadrature phase-shift keying (OQPSK). This modulation scheme is a form of phase-shift keying in which four different phase angles are used. This scheme is sometimes referred to as staggered quadrature phase-shift keying (SQPSK). For offset PSK, the ideal symbol timing for Q is offset by 1/2 of a symbol period from the ideal symbol timing for I. offset is currently only supported for M = 4.

recovered complex waveform specifies 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 the MT Demodulate PSK VI to this parameter.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

input bit stream specifies the demodulated bit stream from the output bit stream parameter of the MT Demodulate PSK VI.

impairment measurement window specifies the window over which impairments are measured.

	start index specifies the index of the first sample of the measurement window. The default is 0.
	width specifies the 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.

impairment definition specifies 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.

Vertical Shear (0)

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 = the specified quadrature skew, in radians

= 10^{(IQ gain imbalance/20)}

a = * b

b =

In matrix form, these equations are represented by

where

Axis Shear (1)

With this option selected, this VI 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:

where

= 10^{(IQ gain imbalance/20)}

φ = the specified quadrature skew, in radians

In matrix form, these equations are represented by

where

reset? specifies how the VI handles bits from partial symbols in the input bit stream. When reset? is set to TRUE, bits making up incomplete symbols are discarded. When reset? is set to FALSE, the VI saves the leftover bits and starts with them on the next iteration. The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

IQ gain imbalance returns the measured ratio of I gain to Q gain, in dB.

Tip For shifted BPSK (also called

/2 BPSK with or without differential encoding), certain measurements, including IQ gain imbalance, quadrature skew, and DC offset measurements, are not performed by the current version of the Modulation Toolkit. The current version of the Modulation Toolkit returns NaN in these cases. Other measurements, specifically modulation error ratio, error vector magnitude, magnitude error, and phase error, are valid and returned for shifted (

/2) BPSK.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

modulation error ratio returns the measured modulation error ratio in dB.

magnitude error returns the measured magnitude error as a percentage of full scale. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

DC offset measurements returns 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.

	I returns the DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	Q returns the DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	origin offset returns the offset, in dB, of the constellation origin from its ideal location.

quadrature skew returns the measured quadrature skew of the complex waveform in degrees.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

MT Measure QAM Quadrature Impairments

This polymorphic instance calculates and reports QAM quadrature impairments.

MT Measure QAM Quadrature Impairments

recovered complex waveform specifies 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 the MT Demodulate QAM VI to this parameter.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

input bit stream specifies the demodulated bit stream from the output bit stream parameter of the MT Demodulate QAM VI.

impairment measurement window specifies the window over which impairments are measured.

	start index specifies the index of the first sample of the measurement window. The default is 0.
	width specifies the 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.

QAM system parameters specifies parameter values defining the QAM system. Wire the QAM system parameters cluster returned by the QAM (M) or QAM (Map) instance of the MT Generate System Parameters VI to this cluster. Do not alter the values.

samples per symbol specifies an even, positive number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate. The default is 16.

Note The Modulation Toolkit demodulation and detector VIs use timing recovery, which is optimized for four or more samples per symbol.

symbol map specifies an ordered array that maps each symbol value to its desired coordinates in the complex plane. The number of QAM states in the array must be 2^N, where N is the number of bits per symbol. The length of the vector for the symbol(s) farthest from the origin must be 1.

impairment definition specifies which set of equations is used to represent impairments.

Vertical Shear (0)

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 = the specified quadrature skew, in radians

= 10^{(IQ gain imbalance/20)}

a = * b

b =

In matrix form, these equations are represented by

where

Axis Shear (1)

where

= 10^{(IQ gain imbalance/20)}

φ = the specified quadrature skew, in radians

In matrix form, these equations are represented by

where

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

IQ gain imbalance returns the measured ratio of I gain to Q gain, in dB.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

modulation error ratio returns the measured modulation error ratio in dB.

magnitude error returns the measured magnitude error as a percentage of full scale. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

DC offset measurements returns 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.

	I returns the DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	Q returns the DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	origin offset returns the offset, in dB, of the constellation origin from its ideal location.

quadrature skew returns the measured quadrature skew of the complex waveform in degrees.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

MT Measure MSK Quadrature Impairments

This polymorphic instance calculates MSK quadrature impairments on a point-by-point basis on the oversampled waveform.

MT Measure MSK Quadrature Impairments

recovered complex waveform specifies 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 the MT Demodulate MSK VI to this parameter.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

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

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies the ideal oversampled waveform as a complex-valued array.

impairment measurement window specifies the window over which impairments are measured.

	start index specifies the index of the first sample of the measurement window. The default is 0.
	width specifies the 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.

samples per symbol specifies the number of samples per symbol in the modulated complex waveform. The default is 16.

impairment definition specifies which set of equations is used to represent impairments.

Vertical Shear (0)

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 = the specified quadrature skew, in radians

= 10^{(IQ gain imbalance/20)}

a = * b

b =

In matrix form, these equations are represented by

where

Axis Shear (1)

where

= 10^{(IQ gain imbalance/20)}

φ = the specified quadrature skew, in radians

In matrix form, these equations are represented by

where

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

IQ gain imbalance returns the measured ratio of I gain to Q gain, in dB.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

modulation error ratio returns the measured modulation error ratio in dB.

magnitude error returns the measured magnitude error as a percentage of full scale. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

DC offset measurements returns 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.

	I returns the DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	Q returns the DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	origin offset returns the offset, in dB, of the constellation origin from its ideal location.

quadrature skew returns the measured quadrature skew of the complex waveform in degrees.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

MT Measure PAM Quadrature Impairments

This polymorphic instance calculates and reports PAM quadrature impairments on a symbol-by-symbol basis at the symbol timing.

Note Certain measurements like I/Q gain imbalance and quadrature skew are not applicable for the PAM modulation format because of the inherently one-dimensional nature of the PAM constellation.

MT Measure PAM Quadrature Impairments

recovered complex waveform specifies 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 the MT Demodulate PAM VI to this parameter.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

input bit stream specifies the demodulated bit stream from the output bit stream parameter of the MT Demodulate PAM VI.

impairment measurement window specifies the window over which impairments are measured.

	start index specifies the index of the first sample of the measurement window. The default is 0.
	width specifies the 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.

PAM system parameters specifies parameter values defining the PAM system. Wire the PAM system parameters cluster returned by either the PAM (M) or PAM (Map) instance of the MT Generate System Parameters VI to this cluster.

	samples per symbol specifies an even, positive number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate. The default is 16.
	symbol map specifies an ordered array that maps each Boolean symbol to its desired coordinates in the complex plane. The number of states in the array must be 2^N, where N is the number of bits per symbol.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

modulation error ratio returns the measured modulation error ratio in dB.

magnitude error returns the measured magnitude error as a percentage of full scale. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

DC offset measurements returns 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.

	I returns the DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	Q returns the DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	origin offset returns the offset, in dB, of the constellation origin from its ideal location.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

MT Measure ASK Quadrature Impairments

This polymorphic instance calculates and reports ASK quadrature impairments on a symbol-by-symbol basis at the symbol timing.

Note Certain measurements like I/Q gain imbalance and quadrature skew are not applicable for the ASK modulation format because of the inherently one-dimensional nature of the ASK constellation.

MT Measure ASK Quadrature Impairments

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

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

input bit stream specifies the demodulated bit stream from the output bit stream parameter of the MT Demodulate ASK VI.

impairment measurement window specifies the window over which impairments are measured.

	start index specifies the index of the first sample of the measurement window. The default is 0.
	width specifies the 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.

ASK system parameters specifies parameter values defining the ASK system. Wire the ASK system parameters cluster returned by the ASK instance of the MT Generate System Parameters VI to this cluster. Do not alter the values.

	samples per symbol specifies an even, positive number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate. The default is 16.
	symbol map specifies an ordered array that maps each symbol to its desired level. The number of ASK levels in the array is 2^N, where N is the number of bits per symbol. The length of the vector for the symbols farthest from the origin is 1.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

modulation error ratio returns the measured modulation error ratio in dB.

magnitude error returns the measured magnitude error as a percentage of full scale. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

DC offset measurements returns 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.

	I returns the DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	Q returns the DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	origin offset returns the offset, in dB, of the constellation origin from its ideal location.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

MT Measure CPM Quadrature Impairments

Measures and reports quadrature impairments over a single user-specified window. This VI must be called once for each measurement window. This polymorphic instance calculates CPM quadrature impairments on a point-by-point basis on the oversampled waveform.

MT Measure CPM Quadrature Impairments

recovered complex waveform specifies 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 the MT Demodulate CPM VI to this parameter.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

detected complex waveform specifies the ideal oversampled waveform. Wire the detected complex waveform parameter of the MT Demodulate CPM VI to this parameter.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies 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.

impairment measurement window specifies the window over which impairments are measured.

	start index specifies the index of the first sample of the measurement window. The default is 0.
	width specifies the 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.

samples per symbol specifies the number of samples per symbol in the modulated complex waveform. The default is 16.

impairment definition specifies which set of equations is used to represent impairments.

Vertical Shear (0)

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 = the specified quadrature skew, in radians

= 10^{(IQ gain imbalance/20)}

a = * b

b =

In matrix form, these equations are represented by

where

Axis Shear (1)

where

= 10^{(IQ gain imbalance/20)}

φ = the specified quadrature skew, in radians

In matrix form, these equations are represented by

where

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

IQ gain imbalance returns the measured ratio of I gain to Q gain, in dB.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

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

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

modulation error ratio returns the measured modulation error ratio in dB.

magnitude error returns the measured magnitude error as a percentage of full scale. Magnitude error is the magnitude difference between the ideal and the actual measured symbol locations.

	RMS measurement returns the rms impairment value calculated over the impairment measurement window.
	peak measurement returns the peak impairment value measured over the impairment measurement window.
	peak symbol index returns the index of the symbol having the peak magnitude of impairment.
	individual symbol measurements returns the impairment value for each individual symbol.

DC offset measurements returns 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.

	I returns the DC offset of the I waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	Q returns the DC offset of the Q waveform, expressed as a percentage of the largest I or Q value in the symbol map.
	origin offset returns the offset, in dB, of the constellation origin from its ideal location.

quadrature skew returns the measured quadrature skew of the complex waveform in degrees.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

Details

For more information about the Vertical Shear definition, refer to Kafadar, Karen. “Statistical Calibration of a Vector Demodulator,” HP Journal: June 1988.

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