Multitap RF canceller with single LMS loop for adaptive co-site broadband interference cancellation

With the development of wireless communication technology, an urgent problem to be solved is co-site broadband interference on independent communication platforms such as satellites, space stations, aircrafts and ships. Also, the problem of strong self-interference rejection should be solved in the co-time co-frequency full duplex mode which realizes spectrum multiplication in 5G communication technology. In the research of such interference rejection, interference cancellation technology has been applied. In order to reject multipath interference, multitap double LMS (Least Mean Square) loop interference cancellation system is often used for cancelling RF (Radio Frequency) domain interference cancelling. However, more taps will lead to a more complex structure of the cancellation system. A novel tap single LMS loop adaptive interference cancellation system was proposed to improve the system compactness and reduce the cost. In addition, a mathematical model was built for the proposed cancellation system, the correlation function of CP2FSK (Continuous Phase Binary Frequency Shift Keying) signal was derived, and the quantitative relationship was established between the correlation function and the interference signal bandwidth and tap delay differential. The steady-state weights and the expression of the average interference cancellation ratio (ICR) were deduced in the scenes of LOS (Line of Sight) interference with antenna swaying on an independent communication platform and indoor multipath interference. The quantitative relationship was deeply analyzed between the interference cancellation performance and the parameters such as antenna swing, LMS loop gain, and interference signal bandwidth, which was verified by simulation experiment. And the performance of the proposed interference cancellation system was compared with that of the traditional double LMS loop cancellation system. The results showed that the compact single LMS loop cancellation system can achieve an average interference rejection capability comparable to the double LMS loop cancellation system.