Advanced methods for I/Q imbalance compensation in communication receivers

I/Q signal processing is widely utilized in today's communication receivers . However, all I/Q processing receiver structures, such as the low-IF recei ver, face a common problem of matching the amplitudes and phases of the I a nd Q branches. In practice, imbalances are unavoidable in the analog front- end, which results in finite and usually insufficient rejection of the imag e frequency band. This causes the image signal to appear as interference on top of the desired signal. We carry out general signal analysis of an imbalanced I processing receiver and propose novel methods for I/Q imbalance compensation using baseband di gital signal processing. A simple structure for compensation is derived, ba sed on a traditional adaptive interference canceller. Improved image reject ion can also be obtained by using more advanced blind source separation tec hniques. Theoretical analysis of the performance of the proposed imbalance compensation structures is presented. In addition, some simulation results are provided in order to further evaluate the performance of the proposed m ethods. The results indicate that the I/Q imbalance can be effectively comp ensated during the normal operation of the receiver, even in the rapidly ch anging case, as long as a linear system model for the imbalance is valid.