Research On The Beidou Receiver Space-time Adaptive Anti-Jamming Technology

Beidou navigation positioning system(BDS) is a global positioning system which is researched and developed independently by China. It can provide all-timer and all-range continuous navigation, positioning and timing, short message service, so BDS plays an important role in many areas of civil and military. In recent years, the application of the global satellite navigation system is widely and rapidly developed. Because of the poor satellite signal power, hostile interference in military and increasingly complex electromagnetic environment, the navigation terminals are susceptible to be interfered not to work. Therefore, at present, all countries attach great importance to the development of the satellite navigation system and the research on the anti-interference of the navigation terminal. Under this background, it is very important to study the interference suppression algorithm of the navigation receiver based on the array antenna.The traditional receiver anti-jamming technology contains of time domain filtering technology, frequency domain filtering and spatial filtering technology. Time domain processing algorithms tends to be complex and poor adaptability; frequency domain processing algorithms suppression effect is not ideal for wideband interference; pure spatial processing algorithm interference number suppressed is limited by the number of array elements and cannot suppress interference signal from navigation signal direction. The space-time joint technology is proposed to carry on the suppression of interference signal, this technology can increase the number of interference suppressd without increasing the array element and can also inhibit broadband, narrowband interference and multipath interference, the receiver anti-jamming capability is significantly improved.The traditional space-time anti-jamming processing algorithm has two shortcomings:(1) the method involves sampling covariance matrix inverse(SMI) operation, needs high computational complexity and cannot guarantee the interference suppression in real time;(2) The traditional method needs to pre-estimate the direction of arrival(DOA) of desired signal direction or reference signal. When the estimated information is inaccurate, the received satellite signals will be damaged seriously, the receivers will lose the ability of positioning and navigation.In view of the high computational complexity of traditional space-time anti-jamming technology, this paper introduces improved two step iterative variable step least mean square error algorithm(LMS) and improved forgetting factor recursive least squares algorithm(RLS)method to calculate the space-time array antenna weighted value to reduce the computational complexity; for space-time anti jamming technology problems depending on a priori information, this paper reduces the output of the vector tracking loop as the space-time antenna array reference information,which avoids the estimation of the desired signal and enhances the robustness of the algorithms. In this paper, we also study the method of adding frequency domain LMS filter to the A/D output of the space-time array antenna to suppress narrowband interference from the navigation signal direction, so as to enhance the interference suppression capability of the navigation receiver. Finally, through the existing receiver platform to collect and process navigation data, the simulation results verify that the algorithm proposed in this paper can significantly reduce the computational complexity, enhance the anti-jamming capability and robustness of the navigation receiver.