Research Of Passive Radar Target Detectionbased On GNSS Signal

The use of outside source for target detection is a kind of passive radar system, whose signal receiver and transmitter is generally in a different place. Different from traditional active radar, the passive radar itself based on external sources does not need to launch detection signal while using third-party non-cooperative signals, such as FM radio signals, TV, GSM mobile communication signal and GPS signal, etc., as the light source. The radiation source signal after exposure to the target will be scatted or reflected, and the passive radar, by receiving the target echo signal and gaining the useful information, completes the detection and position of target. Passive radar signal itself does not need to launch, which greatly improve the performance of their hidden, so it has a strong ability of anti-interference and survival.In this thesis, it uses the signals of GNSS navigation satellite as the radiation source to research the mechanism of passive radar target detection. This thesis mainly use GPS signal as an example to analyze and deduce.To begin with, after analyzing the characteristic of GNSS reflection signals and research status of passive radar, the thesis elaborates the feasibility to use GNSS signals as the radiation source for the passive radar from following aspects, such as the available signal source, signal characteristics, the power of the direct wave and target echo signals and the signal’s fuzzy function and so on.Then the content above, this thesis discusses the methods of location, AOA and TOA/TDOA. Through matlab simulation, it compares their location accuracy and analyzes error sources by GDOP. It also proves that adding receivers and changing their pattern can help to improve the location accuracy. It makes a good foundation for the target location and tracking accurately.After that, it studies the maneuvering target tracking algorithm. On basis of analyzing KF and its extensional algorithms, the thesis achieves the maneuvering target tracking by the method of fundamental location and filtering estimation. In allusion to the existing problems, such as slow error convergence speed and tracking divergent, it proposes an improved algorithm based on the steepest descent and makes some simulations and analysis furtherly. The result shows that the improved algorithm speeds up the convergence speed of tracking error, lowers the probability of tracking divergent, improves the location and tracking accuracy and gains a better tracking result.Finally, in order to gain longer detectable time and get more detection data, the thesis divides the movement process into three phases, rising, smooth running and falling. Combining the geometric diagrams, it deduces the calculation formula of the detectable time under general situations and gives the antenna direction status when gaining the longest detectable time.