Impairment Calibration

I/Q impairments, such as I offset, Q offset, I/Q gain imbalance and I/Q phase skew, degrade the spurious performance of the I/Q modulator. The offsets contribute to carrier suppression. Gain imbalance and phase skew contribute to the creation of an image for the single-sideband RF signal output that is mirrored across the carrier.For a continuous waveform at a frequency +f_s as the baseband signal generated at a carrier frequency of f_c, the expected LO leakage and the image is shown in the following plot.

The image power relative to the desired RF output (ISR), in dBc, is given by the following formula:

where ε represents I/Q gain imbalance

φ represents I/Q skew in radians

The carrier to desired output (CSR), in dBc, is given by the following formula when the output power is 0 dBm:

where α represents volts offset on the I channel

β represents volts offset on the Q channel

Correcting for Temperature Drift

To correct for temperature drift without having to re-initialize a session, call the niRFSG Perform Thermal Correction VI or the niRFSG_PerformThermalCorrection function.

Applying Additional Impairment Correction

You can also apply additional impairment correction with the following properties or attributes: