Research On Multichannel Imaging Technology Of FMCW SAR

Frequency modulated continuous wave synthetic aperture radar(FMCW SAR)is the main developing direction of mini-sized SAR,because of the low system complexity of the FMCW SAR system it has much advantage on volume and weight,in the same time its power consumption and cost are relatively low.Cutting-edge applications not only need the FMCW SAR system to make breakthrough in single parameter but also should meet the demand of the composite index of modern radar,such as high resolution,wide swath,less probability of intercept.Multi-Input Multi-Output(MIMO)radar is an effective solution,compare to single transmitting array and multi-receiving array SAR,MIMO radar can obtain the same spatial sampling rate by using less arrays,this makes it meet the requirements of high resolution and wide swath as well as keep the advantage at miniaturization.What's more,the transmitting antenna and receiving antenna are separated,this will greatly improve the problem of send-receive isolation,so as to increase the integral performance of radar system.In this paper,we combine MIMO technology with FMCW SAR single channel model and Displaced Phase Center Multi-beam in Azimuth(DPC-MAB)multi-channel model is introduced firstly,then the Frequency Modulated Continuous Wave Multi-Input Multi-Output Synthetic Aperture Radar(FMCW MIMO SAR)signal model is given on the basis of FMCW SAR single channel model and DPC-MAB multi-channel model.Analyzing these single models,we can obtain that the basis of FMCW MIMO SAR signal model is DPC-MAB multi-channel model which is based on the FMCW SAR single channel model.During the signal processing of FMCW MIMO SAR,after a series of signal process actions,the processing of FMCW MIMO SAR signal can be divided into multiple single-input and multi-output DPC-MAB SAR signal processing.Using MIMO technology we have to overcome the problem of non-uniform sampling.The non-uniform sampling in azimuth will affect the image quality seriously,so it must be removed.Considering the problem of non-uniform sampling,in this paper,the performance of usual azimuth signal reconstruction algorithms is presented firstly.Then the qualitative analysis for the computational efficiency of these algorithms is given as well as the simulation result of filter blanks method at the situation of overlapped phase centers.According to the simulation result,we obtain that when the phase centers are overlapped filter banks algorithm cannot reconstruct the non-uniformly sampled signal in azimuth,so as to obtain the accurate imaging.Furthermore,this paper proposes a signal reconstruction algorithm based on Fractional Fourier Transform(Fr FT),which has less computing consumption than time-domain reconstruction algorithm,also it overcome the disadvantage of filter banks algorithm,that is when the antenna phase centers become overlapping filter banks algorithm will obtain invalid reconstruction,this improves the image quality greatly.The validity of the proposed algorithm is inspected by using this method within the RD image algorithm.What's more,the validity of this method is verified by using it for point target imaging with RD image algorithm and FMCW MIMO SAR.Finally,in this paper,a preliminary designed experiment system is presented.The detailed introduction of system parameters and the skeleton of system are given.Then,the transmitting and receiving link circuit is introduced in detail.