• NIRFSG_ATTR_IQ_IMPAIRMENT_ENABLED
• NIRFSG_ATTR_IQ_GAIN_IMBALANCE
• NIRFSG_ATTR_IQ_I_OFFSET
• NIRFSG_ATTR_IQ_SKEW
• NIRFSG_ATTR_IQ_OFFSET_UNITS
• NIRFSG_ATTR_IQ_Q_OFFSET

Numeric Value	Data type	Access	Coercion	High Level Functions
1150069	ViBoolean	R/W	None	None

Enables or disables I/Q impairment. The NIRFSG_ATTR_IQ_I_OFFSET, NIRFSG_ATTR_IQ_Q_OFFSET, NIRFSG_ATTR_IQ_GAIN_IMBALANCE, and NIRFSG_ATTR_IQ_SKEW attributes are ignored when the NIRFSG_ATTR_IQ_IMPAIRMENT_ENABLED attribute is disabled.

Defined Values:

VI_TRUE	I/Q impairment is enabled.
VI_FALSE	I/Q impairment is disabled.
Default Value: VI_TRUE

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5830/5831/5832/5840/5841

Numeric Value	Data type	Access	Coercion	High Level Functions
1150072	ViReal64	R/W	None	None

Specifies the gain imbalance of the I/Q modulator (I versus Q).

Gain imbalance is calculated with the following equation:

Units: dB

Valid Values: -6 dB to 6 dB

Default Value: 0 dB

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

Impairment Calibration

Spurious Performance

Numeric Value	Data type	Access	Coercion	High Level Functions
1150070	ViReal64	R/W	None	None

When using a National Instruments AWG module or vector signal transceiver (VST), this attribute specifies the I-signal DC offset. Units are either percent (%) or volts (V), depending on the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute setting.

PXIe-5673/5673E: Actual AWG signal offset is equal to the I/Q modulator offset correction plus the value specified by this attribute. When using an external AWG (non–National Instruments AWG), this attribute is read-only and indicates the I/Q modulator I-offset. Units are volts, as specified by the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute.

Valid Values: -100 to 100% or -0.2 V to 0.2 V

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

Impairment Calibration

Numeric Value	Data type	Access	Coercion	High Level Functions
1150073	ViReal64	R/W	None	None

Specifies the adjustment of the phase angle between the I and Q vectors. If the skew is zero, the phase angle is 90 degrees.

This attribute is ignored when the NIRFSG_ATTR_IQ_IMPAIRMENT_ENABLED attribute is disabled.

Units: degrees (°)

Valid Values: -30° to 30°

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

Impairment Calibration

Numeric Value	Data type	Access	Coercion	High Level Functions
1150081	ViInt32	R/W	None	None

Specifies the units of the NIRFSG_ATTR_IQ_I_OFFSET attribute and NIRFSG_ATTR_IQ_Q_OFFSET attribute. Offset units are either percent or volts.

The AWG or VST offset is the specified percentage of the AWG or VST peak power level when the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute is set to NIRFSG_VAL_PERCENT. Given perfect carrier leakage suppression, the following equation is satisfied

or equivalently

If the NIRFSG_ATTR_IQ_I_OFFSET attribute is set to 100%, NIRFSG_ATTR_IQ_Q_OFFSET attribute is set to 0%, and NIRFSG_ATTR_POWER_LEVEL attribute set to 0 dBm, the desired RF signal is at 0 dBm and the carrier leakage is also at 0 dBm.

Note  For any devices except PXIe-5820, if the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute is set to NIRFSG_VAL_VOLTS, a 0.1 I offset results in a 0.1 V offset in the output. For PXIe-5820 devices, 0.1 I offset results in a 10% offset in the output.

The AWG or VST peak power level changes when settings change in other attributes such as the NIRFSG_ATTR_POWER_LEVEL, NIRFSG_ATTR_FREQUENCY, NIRFSG_ATTR_IQ_SKEW, NIRFSG_ATTR_IQ_GAIN_IMBALANCE, NIRFSG_ATTR_ATTENUATOR_HOLD_ENABLED, and NIRFSG_ATTR_ARB_PRE_FILTER_GAIN attributes. When the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute is set to NIRFSG_VAL_PERCENT, the actual AWG or VST offset changes as the AWG or VST peak power level changes to satisfy the preceding equations. These changes are useful if you are intentionally adding carrier leakage to test the tolerance of a receiver. When the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute is set to NIRFSG_VAL_PERCENT, the carrier leakage, in dBc, remains at a consistent level.

If you are trying to eliminate residual carrier leakage due to calibration inaccuracies or drift, set the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute to NIRFSG_VAL_VOLTS. Offset correction voltage is applied to the I/Q modulator or VST, regardless of changes to the AWG or VST peak power level.

NIRFSG_VAL_PERCENT	Specifies the NIRFSG_ATTR_IQ_I_OFFSET and NIRFSG_ATTR_IQ_Q_OFFSET attribute units as percent.
NIRFSG_VAL_VOLTS	Specifies the NIRFSG_ATTR_IQ_I_OFFSET and NIRFSG_ATTR_IQ_Q_OFFSET attribute units as volts.
Default Value: NIRFSG_VAL_PERCENT

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5830/5831/5832/5840/5841

Numeric Value	Data type	Access	Coercion	High Level Functions
1150071	ViReal64	R/W	None	None

When using a National Instruments AWG module or VST device, this attribute specifies the Q-signal DC offset. Units are either percent (%) or volts (V), depending on the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute setting.

PXIe-5673/5673E: Actual AWG signal offset is equal to the I/Q modulator offset correction plus the value specified by this attribute. When using an external AWG (non–National Instruments AWG), the NIRFSG_ATTR_IQ_Q_OFFSET attribute is read-only and indicates the I/Q modulator Q-offset. Units are volts, as indicated by the NIRFSG_ATTR_IQ_OFFSET_UNITS attribute.

Valid Values: -100% to 100% or -0.2 V to 0.2 V

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

Impairment Calibration