Research On Application Of GPS Nulling Technology Based On Space-time Adaptive Processing

Space-time adaptive processing (STAP) is widely used in signal detection technology in many fields, such as radar, sonar, satellite communications, seismology and so on. The dissertation focuses on adaptive signal processing technology on nulling antenna of satellite receiver. The technology of space-time adaptive nulling antenna analyses the property of input signal in special and time-domain. The technology can greatly promote the freedom of the array antenna in order to raise the number of anti-jam without increasing the number of element of antenna. Especially, it improves capability of satellite receiver for suppressing broadband interferences. STAP is supposed to compute huge matrix which is impossible to be handled by processor, so the signal processing algorithm which can decreases calculation becomes the researching focus now.Taking GPS receiver system as research object, the dissertation probed into the STAP algorithm and space-time adaptive anti-jam technology. And it thoroughly researched the performance of the anti-jam technology. Contributions were summarized as follows:Firstly, the dissertation builts the model of nulling antenna system with the capability of adaptively suppressing interference and achieves special anti-jam nulling technology by adopting RLS algorithm. The model includes satellite signal and interference signal, antenna array, radio frequency processing and signal processing, etc. The dissertation studies the technological data and performance of every model by theoretical analysis and simulating. They formed together the nulling antenna system platform. It has been studied that both mutual coupling of sensor array and channel uncertainties have the influence on adaptive algorithm and correlative technological index since spatial nulling antenna is achieved. Secondly, according to the minimum mean square error (MMSE) criterion, the dissertation puts forward a Space-time least-mean-squares (STLMS) algorithm based on the model of FROST array processing. STLMS is a stochastic gradient algori(?)hm. It has the characteristic:process of recursive operation is simple; computational complexity is small and hardware is easy to establish. It can adjust to the weight of sensor of array antenna in accordance with the amplitude and phase of the incoming interference. STLMS algorithm can suppress interferences in space-frequency domain by increasing the spatial and temporal degree of freedom of nulling antenna, so the algorithm has the capability of suppressing multiple broadband interferences. And the algorithm has the good convergence and misadjustment.T.hirdly, space-time adaptive nulling technology had the good capability of suppressing interference.The dissertation brings in two design projects of space-time nulling technology and used three adaptive processing algorithms. They are the cascaded time-space processing based on RLS algorithm, united space-time processing based on STLMS and multistage nested Winner filter (MSNWF) algorithm, respectively. Compared with space processing, they all enhance the signal to interference and noise ratio (SINR), decrease bit error rate (BER), and improve the performance of the receiver.Fourthly, GPS nulling antenna system is successfully achieved based on STAP. The dissertation introduces the designing idea and technological data of array antenna, radio frequency processing and signal processing module. The system applies FPGA to carrying out STLMS algorithm and accomplished the hardware platform of nulling antenna by debugging. The wire-testing and wireless-testing, especially, associated testing verified that STLMS adaptive processing has better capability of suppressing interference and protecting GPS signal.