This example shows how to use the I/Q Imbalance Compensator block to remove the effects of an amplitude and phase imbalance on a modulated signal.
The model adds I/Q amplitude and phase imbalance to an 8-PSK signal, and then applies I/Q imbalance compensation to correct the impairments. Impairment addition and compensation performed on the signal by using the I/Q Imbalance and I/Q Imbalance to Compensator Coefficient blocks, respectively. The I/Q Imbalance block sets the amplitude imbalance to 5 dB, the phase imbalance to 7 degrees, and DC offset to 0.
The Constellation Diagram blocks display the 8-PSK reference constellation, and the signal constellation before and after impairment correction.
The model runs for 20 seconds, which is not long enough for the impairment compensation to converge. In the Signal with I/Q Imbalance constellation diagram, observe the effects of the amplitude imbalance and phase imbalance on the 8-PSK signal. In the Compensated Signal constellation diagram, observe that the signal is not well aligned with the reference constellation (shown in red).
The compensation algorithm is adaptive and requires time to accurately estimate the I/Q imbalance. Increase the simulation time to 100 seconds and rerun the model. You can see that the constellation is now well aligned with the reference constellation.
You can try changing other simulation parameters, such the step size in the I/Q Imbalance Compensator block, the amplitude and phase imbalance in the I/Q Imbalance block, the modulation type. Then, observe the effects on the Compensated Signal constellation diagram.