A Kalman Filter-Based Method for Real-Time Tracking of I/Q Impairments in Digital Communication Transmitters

Impairments affecting the baseband modulator of digital transmitters, commonly named I/Q impairments, are responsible for deviations of symbols on the I/Q plane from their original position. They consequently cause a reduction of noise margin and can ultimately increase the probability of error. This is the reason why their evaluation is so important in troubleshooting and testing activities. The paper presents an original method for I/Q impairments evaluation, which is based on discrete extended Kalman filter. The proposed method grants as accurate measurement results as alternative solutions present in the literature, but differently from them, it also permits continuous monitoring of active transmitters through real-time tracking of the aforementioned impairments. The results of several experiments carried out on laboratory signals to assess the performance of the method are presented.