Research Of Synthetic Aperture Sonar Imaging Algorithm And MATLAB Simulation

Synthetic aperture sonar(SAS)is one technology of imaging sonar with high resolution.It uses a small aperture arrays of uniform motion along the route,periodically launch chirp signal,and coherent accumulation those received echo signal,then it synthesize a large aperture array.This is the reason why it can achieve the high azimuth resolution.One of the outstanding advantages of SAS is the azimuth resolution that it is only related with the size of aperture,and it is independence of the signal's frequency and the distance between sonar and target.But it also has disadvantages of SAS: Firstly,it has the strict requirement for the movement of array,because it must be coherent for echo signals;Secondly,it had to processing a large amount of data,and the system become more complex.It eased with the development of computer technology.Because it is more mature in SAS domain,the time domain delay-and-add algorithm more used in SAS in China.But when the detection distance become farther,the effective length of SAS become longer,the amount of data which need to be processed is increasing.So the time domain delay-and-add algorithm can't meet the real-time demand.In this article,we choose the frequency-wavenumber algorithm,and analyzed the detail.First of all,we studied the principle of SAS technology,and analyzed the reason why the azimuth resolution in SAS which is independent of the signal's frequency and the distance between sonar and targets.And we detailed study of the effects for the settings of system's parameter when we used the technology of SAS.Then we studied the signal processing techniques which we need to be used on the SAS.It is mainly include: The classical imaging algorithms of SAS(time domain delay-and-add algorithm,Range-Doppler algorithm,Chirp-Scaling algorithm,frequency-wavenumber algorithm);when we used the technology of multi-receiver,the technology of data's fusion and the method of phase's compensation when spatial sampling is uneven should be taken into account,The data fusion can be realization in the time domain or frequency domain,and it is convenience in the frequency domain when need to reconstruction the signal;and the method of compensation about motion error which be caused by the instability of the platform and the complexity of the propagation characteristic about sound in ocean.,about it,we mainly studied the phase gradient autofocus algorithm which mostly used in the array-list,and redundant phase center which mostly used in the multi-receiver.Finally,it can be show by the results of simulation and real data that the almost same of the accuracy between the frequency-wavenumber algorithm and the time domain delay-and-add algorithm,but comparing with the time domain delay-and-add algorithm,the amount of calculation about frequency-wavenumber algorithm is far less.Then comparison of the effects when we using different width of scenarios and different method of interpolation.It is verify that when the target is close to the center of scene,the nearest neighbor interpolation will be able to ensure that the accuracy of final results.And when the hypothesis of “go-stop-go” is not valid,we verify the correctness of the improvements frequency-wavenumber algorithm.