Study On Angle Estimation Method For VHF Radar

Since Very High Frequency(VHF) radar has unique advantages in anti-stealth and anti-radiation missiles, it has attracted the world-wide attention and has become a hot focus in recent years. However, due to long wavelength, wide beamwidth and other factors, the accuracy of angle estimation is very poor. So how to improve the accuracy of angle estimation for VHF radar is an important research direction at present. In this thesis, combining with my actual scientific research tasks and main research topics, some angle measurement methods for VHF radar are studied, and several new improved algorithms are proposed based on the work:First of all, a research is made on several basic angle measurement algorithms for VHF radar. General principle and basic angle measurement methods for radar are introduced simply, including amplitude algorithm, phase algorithm, maximum signal algorithm, centroid algorithm and the monopulse angle estimation algorithms. Simulation experiments are also made to verify the advantages, disadvantages and the performance of these angle measurement algorithms. Simultaneously, some existent problems of these methods are discussed and analyzed. The emphasis is placed on the derivation and theory analysis of Kam angle curve in the monopulse angle estimation algorithms.Secondly, the working principle of machine scanning VHF radar and the theory of conventional monopulse angle estimation algorithms are introduced. On the basis of these, two improved methods are proposed, one is the improved monopulse angle measurement method and the other is the improved beam scanning method. The improved monopulse angle measurement method is based on the principle of half-matrix method. The received data is converted into the Doppler channel by DFT operation, and then except several points are saved the rest points are zeroed in the Doppler channel. After that, IDFT operation is necessary. Then the data which have been processed will be used in monopulse angle estimation. The improved beam scanning method is to build a new cost function. This cost function is established to transform the multiple beam scanning into one search, so that we can get the target’s angle information easily. The computational complexity is reduced greatly, what’s more,the simulation results show that the performance of these two improved algorithms is significantly more excellent than conventional algorithms.Next, the basic principle and structural model of distributed VHF radar are introduced. A study on the rough and accurate estimation method based on the ESPRIT algorithm is made. Rough estimation is one of the proper properties of distributed radars. Estimated values of large variance and no illegibility are got from rough estimation, while small variance and illegibility from accurate estimation. Therefore, the estimations should be searched optimally for the real target’s angle. Theory analysis and simulation results show that both methods perform well in angle estimation, and the accurate method is better than the rough one.Finally, according to the structural characteristics of distributed VHF radar, a further analysis is made of the impact of baseline length on the angle measurement accuracy. With the increase of baseline length, the performance of angle estimation for distributed VHF radar has a “V” shaped variation. Associated with this character, a method for determining the optimal baseline length is proposed. Through this method, the optimal baseline length can be ascertained, and the angle eatimation error caused by the structure of distributed VHF radar is reduced. The effectiveness of this method is validated by computer simulation results.