Study On The Space-Time Adaptive Processing For Anti-Jamming Antennas Applied To Satellite Navigation Positioning Terminals

With the rapid development of wireless communication technology, lots of electromagnetic signals surround us, among which some are interference or jamming ones having serious impact on the useful signal receiving. In order to reduce or eliminate these non-useful interferences, a space-time adaptive processing (STAP) technology, based on a nulling method in space-time domain, was proposed to suppress the signals in certain wavebands coming from special incident angles. Especially in the satellite navigation system, due to that the navigating signals arriving on the ground are very weak, it is more important to take some necessary measures to reduce jamming signals. In the thesis, applying the STAP algorithm on the Beidou navigation satellite system (BDS) terminals is presented and investigated.First, a mathematical model of space adaptive processing (SAP) is built, and then the optimal weight vector expressions are deduced under four different criterions, such as maximum signal to interference ratio criterion (MSIR), minimum mean squared error (MMSE) criterion, maximum likelihood (ML) criterion and minimum variance (MV) criterion. Meanwhile, the four corresponding angle response functions (ARF) are given too. According to the characteristics of satellite navigating signals, the power inversion (PI) algorithm simplified from the MV criterion is chosen here. Furthermore, both ARF matlab model of the four-cell compact rectangular and Y-type circular arrays are built, simulated and optimized, which show that anti-jamming capability (AJC) of the former is better when the optimal reference cell is chosen. Actually, both mutual coupling and channel uncertainty effects on the adaptive algorithm are considered during simulation in detail and some conclusions are obtained:1) the AJC becomes weak due to the channel uncertainty while one jamming exists; 2) the AJC becomes worse dramatically due to the mutual coupling, especially for super strong jamming signals. Thus, some suggestions including compensating mutual coupling matrix in software, directly reducing mutual coupling in hardware, and etc. are presented to reduce mutual coupling effect in the system.Second, similarly, a mathematical model of space-time adaptive processing (STAP) is built too and the optimal weight vector expression is deduced under MV criterion of the constraint condition assuming that the steering vector is a unit vector. In the corresponding matlab model, the time-parameter is optimized while strong Gaussian noises exist, which is helpful to decide time-delay orders and snapshot numbers. Moreover, some other two interferences, such as periodical pulse trains and frequency-modulation signal, are considered in the simulation. All the work shows that it is hard to find a general group of parameters to be adaptable to the different kinds of interferences.Finally, a four-cell micro-strip antenna array model is built and optimized in HFSS software and then sample designing, processing and testing are completed. Comparing the simulated data of the antenna array to the measured, there are very close to each other. Unfortunately, the test results from a jamming test system are not very consistent to the simulated, which may be led by the MC effect, data processing precision, the concrete adopted algorithm, and etc.