IQ Impairment:Offset Units Property

NI RF Signal Generators Help (NI-RFSG 18.1)


Edition Date: June 2018
Part Number: 371025V-01
View Product Info

Download Help (Windows Only)


NI-RFSG 18.1 Help
NI-RFSG 18.2.1 Help
NI-RFSG 19.1 Help

Short Name: Offset Units

Property of niRFSG

Specifies the units of the I Offset property and the Q Offset property. Offset units are either percent (%) or volts (V).

Supported Devices: PXIe-5644/5645/5646, PXIe-5673/5673E, PXIe-5820/5840

Default Value: Percent

The AWG or VST offset is the specified percentage of the AWG or VST peak power level when the Offset Units property is set to Percent. Given perfect carrier leakage suppression, the following equation is satisfied:

or equivalently,

If the I Offset property is set to 100%, the Q Offset property is set to 0%, and the Power Level (dBm) property is set to 0 dBm, the desired RF signal is at 0 dBm and the carrier leakage is also at 0 dBm.

The AWG or VST peak power level changes when settings change in other properties such as the Power Level (dBm), Frequency (Hz), IQ Skew (Degrees), Gain Imbalance (dB), Attenuator Hold Enabled, and Arb Pre-filter Gain (dB) properties. When the Offset Units property is set to Percent, the actual AWG or VST offset changes as the AWG or VST peak power level changes in order 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 Offset Units property is set to 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 Offset Units property to volts. Offset correction voltage is applied to the I/Q modulator or VST, regardless of changes to the AWG or VST peak power level.

Percent (11000)

Specifies the I Offset and Q Offset property units as percent.

Volts (11001)

Specifies the I Offset and Q Offset property units as volts.

Remarks

The following table lists the characteristics of this property.

Datatype iL
PermissionsRead/Write
High-level VIs N/A
Channel-based No
ResettableYes

WAS THIS ARTICLE HELPFUL?

Not Helpful