Research On The Signal Pre-processing In Lightning Detection System And Comparison Of Localization Algorithms

As a destructive natural phenomena, lightning brings lots of casualties and economic loss. Many measures have been taken to predict lightning. However, due to the limit of measuring technique on lightning, people know little about the process of lightning. Given the shortage of lightning parameter and the weakness of design, the damage from lightning still can not be predictable well. In order to enhance the speed and accuracy of lightning location, we need to design a more effective system that is appropriate with physical mechanism of thunder and lightning. So this paper conduct the work of research on signal pre-processing in lightning with VHF (Very High Frequency) band detection system and positioning technology. With the help of MATLAB,we can acquire the results of DO A (Direction Of Arrival) estimation using three algorithms respectively. Then,compare and analysis the results.Array signal processing system is commonly used in VHF band lightning detection system.First, the system convert the analog signal received by antenna to digital signal,multi-channel high speed bit flow is formed by A/D conversion,then,the parameters which is necessary in lightning location system are acquired from signal processing. Before signal processing,we need to deal with the multiplexed signal data received by antenna previously.Data pre-process in lightning detection system include detecting the information about the state when lightning happens,high speed multiplexer signal down conversion processing and forming covariance matrix,then,with this processed data,we can estimate the direction of arrival signal.In this paper,the state information when lightning happen is detected by the technique of optimal threshold method,with the help of this technique,the sum of false alarm probability and leakage alarm probability diminish. With the help of MATLAB,digital down conversion is simulated and covariance matrix generation module is completed by SIMULINK.TDOA(Time Difference of arrival) and DOA(Direction of arrival) are two common location methods,they are always used in VHF lightning detection system.In this paper,some location methods and algorithm used in DOA are analyzed.Based on the classical algorithm, a sparse robust Capon beam forming algorithm and improvement MUSIC (Multiple Signal Classification) algorithm are presented.Compare the two algorithm with available algorithm,analysis the performance of the two algorithm by software MATLAB. Analysis the results of DOA estimation by using Delay-add algorithm, Capon algorithm and improvement MUSIC algorithm respectively, from the result we can conclude that Capon algorithm perform best in DOA estimation among the three algorithm,improvement MUSIC algorithm is in the middle, Delay-Add algorithm have the worst performance.