Research On Distributed ISAR Imaging Technology

Distributed ISAR is a new type of radar that has been used to image non-cooperative targets in recent years.It has important application potential and value in battlefield detection and homeland defense.The difference from the traditional single-station ISAR is that the distributed ISAR adopts spatially separated transmitting and receiving array elements,and an equivalent spontaneous self-receiving element can be formed between any transmitting array element and any receiving array element.Through reasonable deployment,multiple equivalent elements located at different observation angles simultaneously observe the target.The relative rotation between the target and the equivalent element is used to fill the angular separation between the elements of the equivalent elements,thus forming a large observation angle.It can not only overcome the situation that the single station ISAR can not obtain a large observation angle under the limited motion of the target itself,but also has the potential of high azimuth.At the same time,because the system is placed in space,it also has strong battlefield survivability and anti-stealth capability.Firstly,this paper establishes the echo model of distributed ISAR,analyzes the principle of distributed ISAR to improve the azimuth resolution,and simulates and analyzes the equivalent array element echo observation angle without interval,no overlap,interval,overlap.Basic imaging methods in different situations.Then,this paper studies the distributed ISAR echo joint sparse processing method.If there is a small interval between the observation angles of the equivalent elements,the existing method usually uses interpolation to recover the missing data and then process it.However,when the observation angle interval is too large or the echo signal noise is relatively low,the interpolation method is difficult to obtain accurate results.Therefore,for the large interval of echo,the echo is sparsely represented and solved by orthogonal matching pursuit(OMP).At the same time,the sparse solution method is also applicable to the case where the point target is not rotating at a constant speed.It is verified that the stability and applicability are better than the traditional interpolation method when the echo interval is large and the signal-to-noise ratio is low.Finally,the paper also studies the incoherent fusion of sub-images.The imaging quality of high-speed maneuvering and stealth targets is easily affected by the observation angle and target motion.In this chapter,the target echoes obtained from different observation angles of distributed ISAR are used for single-station ISAR imaging and then image fusion,which can overcome the RCS fluctuation of stealth target and improve the stability of the image.In order to overcome the influence of the non-uniform rotation of the high maneuvering target on the azimuth imaging of the substation after the translational compensation,we use the Matched Fourier Transform(MFT)to perform the ISAR imaging of the substation.