Passive Detection Based On Loran-C System Feasibility Study

This paper revolves around the feasibility of passive detection through the using of Loran-C system, as the subject relevant research work, the main purpose is to verify whether the Loran-C system can be passive detection or not, and based on the Loran-C system for this purpose in theory and practical respectively passive detection done on the feasibility of certain exploration. Specific work as follows:1. Introduce Loran-C system, mainly include the principle of hyperbolic positioning, transmitted signal, Loran-C station chains constituting principles and detailed exposition of the pulse-code each station chain parity cycle and their roles. Analyzes the types of Loran-C system interference signals encountered at work, summed up various interference suppression methods and the advantages and disadvantages of these interference suppression methods. Finally, a problem that in the cycle identification of Loran-C signal, groundwave and skywave latency estimation should be solved urgently have been introduced. Through the introduction of the importance of the skywave latency estimation, and then introduces a number of algorithms for solving skywave latency. At last, summarize the characteristics of these algorithms.2. From the theory requirements of passive detection system as the beginning, do the large amount of quantitative analysis and simulation experiments, from the choice of the matched filter coefficients to Loran-C signal, the resolution of distance and speed for the Loran-C signal, and nalysis the phase congruency of Loran-C signal and do other aspects the relevant work. From these simulations we can get a lot of information, there are great differences between the matched filter coefficients and the actual transmission signal generated by the simulation, as the matched filter coefficients, although the launch signal has a tailing phenomenon, but when the matching filter, also need to be coupled to the signal from the transmitting station as a matched filter coefficients according to the actual situation factor, so as to ensure that not in mismatched filtering state. The range resolution of Loran-C signal is bad, consider using the doppler information to distinguish the targets, that is, from the union of two-dimensional of the distance and doppler to detect targets. If we want to make use of Loran-C signal doppler characteristics to target detection, we need takes longer coherent integration, it is need to consider the problem of Loran-C signal long coherent accumulation. For phasecongruency, Pucheng station transmitting signals is better than Chongzuo station transmitting signals, but through the contrast of theirself emission signals can be seen that the phase coherence Chongzuo station transmits signals emitted signal is better than Pucheng, and with the theoreticcal the simulation signal comparison, the phase behavior of the tail in Chongzuo station transmit signal is not good Pucheng station transmits in the signal phase preserving characteristics.3. Explore the Loran-C signal on the feasibility of detect- ing surface targets, primarily process and analysis the measured signal. Processing the measured signal is also fall across a considerable number of issues, when encountered in the acquisition of the echo signal envelope and phase of walking problems, find out that the sampling clock signal with the transmitted signal clocks are not synchronized, last resulting in a frequency offset. Analysis the spectral from the slow time to the echo signal, to obtain a frequency deviation. Then compensate the frequency offset, and have a good effects. Directly use the method of direct wave is set to zero signal processing methods for processing the measured signal, processing result is not good. With the phase-coded pulse groups parity Loran-C system are complementary code feature, the measured data were matched filter processing of pulses, the results of the processing of unsatisfactory. Finally, in order to facilitate intuitive, effective and fast processing and analysis Loran-C measured data, to design and develop a software that based on MATLAB GUI technology to process measured data which is based on Loran-C system passive detection, mainly use the preceding article of the signal processing algorithms, according to the actual using, testing and verification, the software can be stable and effective, rapid completion of the target of process measured data.