Research On Preprocessing-based Locating Countermeasures Technology For Passive Locating System

In passive location system, the passive location target does not transmit dedicated locating signal. The locating of passive target was implemented by receiving and processing of the common electromagnetic signal radiated by it. Traditional active location devices, such as radar and sonar, will transmit high power electromagnetic wave, increasing the risk of the anti-radiation weapon and the threat of electromagnetic interference. Passive location system cames to be a new kind of electronic reconnaissance technology, because of its unique advantage of concealment and mobility, attracted more and more attention in the field of electronic countermeasures. In recent years, with the rapid development of signal processing technology in communication and radar receiver, passive locating system can support almost all function of the active radar system with increasing positioning precision. Passive location system has been well studied, but the study of locating countermeasures was rare. It is urgent to research on locating countermeasures technology for passive location system.In this thesis, the basic principle of the traditional TDOA location was given, its positioning performance was studied. According to the interference factor which affected the accuracy of the traditional TDOA location, a preprocessing-based locating countermeasures technology for passive location was proposed. The anti-location performance of the preprocessing-based locating countermeasures technology was studied and the location performance for the cooperational devices was verified. This thesis is organized as follows.(1) Based on the TDOA location theory, the TDOA location precision was significantly effected by the time delay estimation precision and the signal-to-noise ratio(SNR) of receiving signal. In wireless transmission, the time delay estimation precision was decreased by the multipath fading. According to these analysis, a pseudo-multipathbased signal preprocessing method was proposed. The pseudo-multipath signal transimitted by the passive location target could interfere and deceive the noncooperational devices, causing the decrease in location accuracy.(2) Based on the theory mentioned above, a modeling based on the pseudo-multipath signal preprocessing was implemented, and impact of the preprocessing parameters on the time delay estimation precision and location accuracy was analyzed based on our model. The simulation results show that proposed locating countermeasures technology could significantly decrease the location accuracy of non-coopeartional devices using traditional TDOA method.(3) Through the detailed formula deductionand simulation analysis, the impact of SNR, time delay, amplitude factor, and the preprocessing parameters on the TDOA location geometric factor(GDOP) was studied. In particular, the influence of time delay estimation and location accuracy caused by the pseudo-multipath preprocessing with different parameters was researched.(4) The location performance for the cooperational devices was verified by using the known preprocessing and transmitting signal parameters of TDOA location target. Research has shown that the cooperational devices have better location performance than traditional devices caused by the diversity characteristics of pseudo-multipath diversity.