Research On Satellite Interference Location

Since satellite transmitter is transparent for all signals that arrive at its receiving antenna, the position and frequency of the working satellite are extensively used, so the system of the satellite communications is very frail and will be disturbed easily.For those interferences which last a long time and effect communication services badly, adopting accurate TLS (transmitter location system) technique to find out interference is an important problem to discuss for easing disturbing and enhancing systemic security.In present-day electronic battle, it is also significant that we locate interference in order to destroy target.For the moment,there are two kind of mature systems of satellite interference location—the TLS Model 2000 of America and the SatID of the U.K, whose theory is essentially uniform.They both base on the system of double- satellite of TDOA and FDOA.The TLS technique is applied extensively in satellite system of military affairs and civil application in INTELSAT ,EUTELSAT,America and the U.K.It deals with thousands of interferential events. The precision of location is less than ten kilometer.The system of satellite interference location involves many fields. It solves a lot of problems of interferential events that may be purposive or unmeant, and ensures our legitimate rights and interests.The technique of satellite interference location has been mature abroad, but it is still faulty in our country. So pressing on with our research, going in for more perfectly techniques of location, better precision and quicker speed are still our main task.In this thesis, it studies deeply the methods of based on second-order and fourth-order cumulant of time-delay of arrival (TDOA), frequency-delay of arrival (FDOA) and joint estimation location technology.The simulation results show that the joint method can make up the blur problem in time difference method and the velocity vector unknown problem in Doppler frequency method.So this thesis has theory meaning and actual value in some extent.It proves that the methods are both practical and promising.In this thesis, we have analyzed two or three methods of TDOA, FDOA, and TDOA&FDOA joint estimation, at the same time compared their accuracy of estimation. Although TDOA&FDOA joint estimation is more complex, it's also more accurate and will lead the future.This dissertation studies the problem of satellite interference location systematically.It lays the foundation for the design on the system of double- satellite location system and further reseach.The main contents are as following:Chapter one: In the thesis, the history, significance and evolution of the satellite interference location are reviewed. The interferential reason of satellite communication system, the means of locating unknown target and the arrangement of the thesis'content are presented respectively.Chapter two: The model of satellite interference location in common use—double-satellite location system is introduced. The thesis studies the theory,configuration and algorithm of the double-satellite location system, and then gets the difference between them on the study of three-satellite time-difference localization algorithm,four-satellite time-difference localization algorithm and double-satellite localization algorithm.The theory of double-satellite location is found on time-delay of arrival (TDOA) and frequency-delay of arrival (FDOA) location technology.The track gained by TDOA is hyperboloid which intersects with spherical surface under the konwn information of two satellites, then we get a curve. Another curve gives birth to intersect of FDOA and spherical surface. Finally, get an elliptical area which is the area of interference. And the position of interference can be ascertained by virtue of data-base or other secondary measures.Chapter three: Elicite the basic theories of parameter estimation.In practice, the measure of parameters is important.Because the information which needs to be thansfered is modulated in the parameters. Of course, there are many other parameters for application except TDOA and FDOA, such as angle, distance. By reason of our need, TDOA and FDOA will be introduced mainly in the chapter.About TDOA: Introduce the ways of matlab function, directly and parametric double-spectrum, also give simulation under different conditions. A better result is gained according to altering the formula of the way of directly double-spectrum.The method of parameter double-spectrum doesn't adopt the algorithm of FFT, so it is steadier than the way of directly double-spectrum which makes use of FFT to estimat time-delay.About FDOA: Introduce some basic methods which are based on second-order and fourth-order cumulant, put forward some algorithms and make out a series of simulations. The results show that when signal is mixed with the correlative noise, the way of FDOA estimateion based on the fourth-order cumulant is valid and feasible. However, the way based on second-order cumulant brings deteriorative result.Chapter four: The algorithms of based on second-order and fourth-order cumulant which are used to estimate TDOA and FDOA simultaneously derive out.In this chapter, a joint estimation of the parameters of TDOA and FDOA on satellite interference location is introduced. Analyze receiving signals, and put up the TDOA&FDOA joint estimation algorithm firstly. And then second-order and fourth-order cross ambiguity function are presented concretely.The method of CAF-SOS provides higher estimate accuracy through the simulation, but not for color noise, because the method of CAF-SOS is sensitive to correlative noises.The method of CAF-HOS can meet color noise with Gauss distribution,but possesses slow data convergence performance and high calculation load. Ambiguity function is a very useful tool which can obtain quite accurate value. Taking into account of different data lengths, different noises and different SNR, we simulate and get some useful conclusion. The computer simulation results show the fourth-order cumulant is valid and feasible. Chapter five: First of all, elicit the model of location, and then find the means of location, at last introduce how the location comes true. It is the application of TDOA and FDOA in satellite interference location. The chapter mainly describes two principles of location: geometric principle and algebra principle. According to the principles, we can locate the interference through seeking the point of intersection of hyperbola or iterative calculation.At the end of the chapter, some things about the whole working flow, working condition and location precision are generalized.The whole process can be described as following: it utilizes two receiving antennas which are used to receive signals that are transmitted by satellites, and resorts to a series of means like frequency conversion, A/D conversion, the compare of relativity, brings TDOA and FDOA lastly. So the position of interference can come true by virtue of data-base or other secondary measure.Finally: An overview of author's work and the prospect of technique of satellite interference location are presented.