Research On The Methods Of Radar Coincidence Imaging Based On Static Targets

The traditional SAR imaging is in a squint model, and the different information loaded in target echoes can be collected by relative motions between radar and targets. Through the analysis of the static target imaging mechanism, except for the real aperture imaging technique, radar imaging technique in focal plane based on the offset-focus feed can also be acquired. This kind of method is not suitable for long distance imaging with a poor azimuth resolution by using optical lens. Therefore, based on the study of intensity coincidence imaging in the optical system, a high-resolution imaging system is constructed which is similar to "ghost" imaging.Firstly, based on the unique characteristic of array signals, a new active milimeter imaging model is established. The imaging resolution has a great relationship with the array dimensions, distance between the antenna elements and the targets.The changes of the parameters above can influence images' quality. The simulation experiments verify the theoretical resolution by target image and response contour.Secondly, the electromagnetic process is analyzed and the integral models of the incident and reflection process are constructed in detail. The echo matrix, radiation field matrix and target scattering coefficient matrix can lead to the analyses of rank, vector, correlation, and solution. Aiming at different signal to noise ratios,the algorithms of direct correlation and the optimization solution can both reconstruct the targets.Lastly, two kinds of methods to improve the randomness of the radiation field are presented by theoretical analysis and simulation experiments. Schmidt orthogonalization and its revised version to the radiation field matrix are the first method. In the revised version, the orthogonal calculation to each column vector is instead of each row. The first row vector orthogonalizes with the other row vectors and the output matrix orthogonalizes with the third row vector. By this analogy, the corresponding output row vectors are stored in the radiation field matrix. The second method is to construct three types of array antenna-symmetric array antenna, irregular array antenna and circuiting array antenna. The following two questions are studied seriously,(1)the specific form of the source matrix including the transmitting matrix and the delay matrix, and the form has a direct relation to a more complicated radiation field in order to improve the resolution;(2)the influence on the imaging quality by the rotation velocity and the pulse transmitting frequency. Simulation experiments show the random property of radiation field is effectively improved and the imaging quality is greatly improved through the Schmidt orthogonalization and the changes of the array form.