Research On The Key Technologies Of The Cosite Interference Cancellation

With the rapid development of communication industry, the wireless communication has a broad development space not only in the military field but also in civilian domain. But the cosite interference causes a serious influence on the performance of the communication equipments. With the development of adaptive signal processing, the adaptive interference cancellation technology, whose nucleus is the adaptive wiener filter, has become one of the common methods to solve the problem of cosite interference. In order to cancel the interference signal, the weighted coefficient of the filter is adjusted continuously according to some certain standard, which makes the amplitude and phase of the output signal and the reference signal synchronous. As far as the adaptive interference cancellation technology been studied, the existing key technologies are mainly applied to adjacent frequency domain full-duplex communication system. These technologies mainly include three aspects: the antenna spacing and position adjustment, the interference cancellation in the analog domain and the interference cancellation in digital domain. This paper mainly studies the key technologies of the analog interference cancellation before the receiver.The common key technologies of analog interference cancellation mainly collect the interference signal at the transmitter and take the adaptive algorithm to adjust the amplitude and phase of this correlative signal to realize the interference cancellation at the receiver. Although this method can solve the problem of the interference cancellation in the analog domain, it remains to be optimized for systems with space limitations. This paper proposes a new scheme to realize the interference cancellation in RF domain only by applying signal process in the receiver, which not only saves the system space but also reduces the system complexity.In this paper, firstly the problem of cosite interference, the research situation at home and abroad and the related technology of adaptive interference cancellation are introduced. Secondly, the existing key technologies of the cosite interference cancellation are analyzed. Thirdly, a new scheme which can offset the interference signal is put forward, and the key technologies of this scheme, including anti-alias filter, ADC and DAC, the fractional delay filter, the fractional time delay estimation, channel equalization algorithm and smoothing filter are researched. In addition, we introduce the overall scheme and analyze the signal processing of the whole scheme in theory. Finally, the simulations of these technologies we select, including the different influence between the big signal and the little signal in the process of ADC, the performance analysis of fractional delay filter and fractional delay estimation and convergence performance of BLMS are given. Moreover, the simulation of the whole system is provided to verify the feasibility of the scheme in theory. The simulation results show that the ICR of this scheme interference can reach more than 35 d B in 200MHz~400MHz, which can satisfy the demand of interference cancellation.In conclusion, the proposed scheme is applicable to the interference cancellation at a certain frequency range in analog domain and the biggest advantage of this approach is only a signal process in the receiver is needed. For systems with space limitation, this study reduces the complexity of the system. Due to domestic related research is less and after searching in several academic databases, the proposed scheme is said to be a pioneering research in this field, and a related national defense patent for it has been applied.