Research On Key Techniques Of Doppler Direction Finding System

With the development of radio communication technology,courage of radio direction finding is more and more widely,Doppler direction finding technology has got widespread application. During the recent century,the development of Doppler direction finder is very rapid. The factories has taken a series of new technology to make full use of the advantages which are accuracy, sensitivity and small polarization error of Doppler direction finder,improving the performance of finder. Doppler direction has a close relation to radio monitoring of our country. Combined with the process and development of radio monitoring and direction finding in China,it is very important to design and develop single channel Doppler direction finders for short wave or ultrashort wave with excellent performance to promote the growth of radio monitoring in China.This paper selects the single channel Doppler direction finding based on the introduction and comparison of various Doppler direction finding methods,proposes a method on how to find direction,and designs and simulates a single channel Doppler direction finding system for ultrashort wave. The thesis expounds the principle of this direction finding system in detail,the algorithm on calculating the direction angle of arriving wave,the component of the system and the performance simulation with the computer. At last,the direction-finding error is given by calculating the difference between theoretic calculation value and actual measurement. In this system,the input signal is comprehensive sampled and filtered to enhance the accuracy of direction finding.For the Doppler direction-finding system, one of the most critical part is how to accurately capture the carrier in order to process signal. So the carrier synchronization and tracking is very important. This paper studies the carrier synchronization method which has commonly used in recent years, and introduces various kinds of carrier synchronization methods, mainly includes the basic phase lock loop(PLL), a special phase lock loop, cross-dot frequency tracking technology based on FFT. Finally we chose the cross-dot frequency tracking technology based on FFT to apply to actual system, and present a corresponding computer simulation to analyze the effect of carrier capture and tracking...