Research On Direction Finding Techniques Based On Space Spectrum Estimation

In recent years, the progresses of large scale integrated circuit and mobile communications have promoted the development of wireless local area network and mobile communication network, the various signal pattern , frequency and function of radio are made complicated in space, and the form diversifies, objectively, require that the radio terminal is able to adapt to many patterns, multifrequency, multifunctional environment. Therefore, in the process of using, planning and creating, the radio consumer longs to be able to predict and describ the states of complicated space radio signals using RKRL(Radio Knowledge Representation Language), include DOA(Direction Of Arrival), frequency, power, modulation modes, signal channel encode, frame structure, etc.. Then analyse on this complicated state space rationally, thereby make reasonal choices. Among them, direction cognition is the most fundamental target. How to realize the direction cognition of radio signals effectively, exactly and quickly, has attracted more and more attention. Researches on space array signal processing based radio direction finding methods have come to be hot spots all over the world. In the actual application, resolution response, precision, expansibility and real-time response have become the most important indexes to appraise the radio direction finding methods. Spatial spectral estimation method is a new development direction of array signal process technology which satisfies perfectly the applicative requirements of radio direction finding. Supported by the projects of"Software System Structure based Radio Cognition Studies"and"Location Technology Studies in Wireless Local Area Network and Mobile Communication", this thesis has engaged in extensive research on some relevant basic theories, implementation methods of spatial spectral estimation and the resolution response, precision, expansibility and real-time response of radio direction finding method based on spatial spectral estimation.In this thesis, we analyze the background and features and give the models of radio direction finding technology based on spatial spectral estimation. Then select MUSIC and Cyclic-MUSIC algorithm as basic algorithm to study roundly based on the analysis and remark of status and problems remaining unsolved. In the meantime, give the technology and implementation method for radio direction finding based on the application background of the research. Spatial spectral estimation is a super-resolution technique. We analyze the super-resolution principle of spatial spectral estimation, present an improved super resolution method based on MUSIC algorithm for estimating the DOA of signals. The proposed method expands a real sensor array into several virtual arrays to enhance the resolution, each virtual array has a different aperture size which is bigger than the original array's, and aperture expanding results in spurious peaks of spatial spectrum, then the proposed method averages the spatial spectrum of the virtual arrays to restrain the spurious peaks. Simulation results show the effectiveness of the method, and prove the method has a higher close-target resolution than standard MUSIC algorithm for incoherent signals.Cyclic-MUSIC algorithm as an advanced method for DOA estimation under complicated radio environment, it has much better anti-jamming and anti-noise performance than MUSIC algorithm. We analyze the bias of Cyclic MUSIC algorithm, explore the effects of carrier frequency, signal bandwidth, cyclic frequency, sensors distance, and DOA angle on the performance of DOA estimation. Then propose an improved cyclic MUSIC algorithm based on the result of the analysis, and reduces the bias substantially by properly choosing the frequency for evaluating the steering vector. Simulation results show the exactitude of the error analysis and the effectiveness of the improved algorithms.2D-DOA estimation is an important problem of radio direction finding application. We introduce the concept of 2D-DOA estimation, and then standard MUSIC and Cyclic-MUSIC algorithm are applied to 3D rectangular formed 2D-DOA estimation. Then we give the basic signal models; and apply Eextended-Cyclic-MUSIC algorithm for enhancing close-target resolution; to avoid spectral peak searching in angle domain, the approach is finding roots of complex function in z-domain, which is similar to root-MUSIC algorithm. As a result, the new algorithm improves the performance of estimating DOA greatly with less sensor requirement and less calculation. In the meantime, the method has a higher close-target resolution than Eextended-Cyclic- MUSIC algorithm.Based on the basic theory of direction finding techniques, a data process system based on high-speed parallel optimization algorithm is designed and developed. The thesis describes the design idea of high-speed parallel optimization algorithm, gives the feasibility analysis, and proves the feasibility by computer simulation. We establishe the system model and overall framework, gives the definition and functions of related modules, and give the integrated simulation and contrast performance test of the system, the system is proved to be efficient through the performance test. This prototype system realizes the core functions of direction finding system and establishes a solid foundation for putting direction finding products into practice.In conclusion, we propose the further development directions of direction finding system.