Research On Optronic Radar Signal Processing

The increasement of resolution,bandwidth and the number of channels has led to a higher demand on data processing capacity and speed.For the demand of massive and high-speed data processing,digital processing technology has or will soon expose limitations in computing speed and power consumption.On this background,optronic processing has been developed for radar signal processing.The technology utilizes spatial optical information processing to complete the complex mathematical computing of massive data and applies electronic processing to complete logic operations and sequential control.Owing to high-speed parallel processing and high-density data carrying capacity,this technology has the potential to provide massive data processing and real-time processing for radar systems.Moreover,the processing mainly relies on passive optical components with low power consumption and anti-electromagnetic interference capacity.In this paper,optronic radar signal processing is thoroughly studied.Firstly,the research on high-speed spatial light modulation is carried out,and a novel joint amplitude and phase control(JAPC)method of spatial light using a digital micromirror device(DMD)is proposed.This technology is indispensable for the realization of optronic processing.An off-axis 4f-configuration and a DMD pattern formation algorithm based on mixed integer programming are required for the implementation of the proposed method.As the correlations among all pixels in the modulation result is fully considered,the proposed method has higher modulation precision compared with conventional methods.JAPC method has a superior performance in modulation speed by using a high-speed DMD.It also has the capability of independently and simultaneously controlling amplitude and phase of laser beams,which makes it possible to encode arbitrary complex signal onto laser beams.Then,the research on optronic beamforming of phased array radar signals is carried out,and a real-time optronic beamforming(OPBF)system on receive is proposed.The system is suitable for real-time processing of massive phased array radar data,such as large phased array and multiple beams.In this system,radar raw data and weighting coefficients are both encoded on the laser beams.Radar data is then weighted and summed in the optical domain to obtain the beamforming result.And radar data of all channels are processed in parallel and multiple beams are generated concurrently.Due to the high-speed parallel processing characteristics,compared with DBF,OPBF has a significant advantage in processing speed for massive data.Moreover,the processing speed will not be affected by the increase in the number of array elements and forming beams.Additionally,OPBF system is suitable for narrowband beamforming as well as wideband beamforming.Next,the research on optronic processing of synthetic aperture radar signals is carried out,and a real-time optronic high-resolution synthetic aperture radar(SAR)imaging system is proposed.In this scheme,SAR raw data is encoded on the laser beams,and the modulated laser beams pass through a lens system to form a SAR image.The system has a superior performance of real-time imaging.With the help of subaperture architecture,the proposed system enables optically processing large-scale SAR data in parallel by multiple optical subaperture processing modules.Therefore,the system is able to process high-resolution SAR signals and generate full-resolution SAR image in real time.Moreover,owing to the subaperture structure,the data scale is easy to expand.Finally,the research on optronic encoding in netted radar system is carried out,and a high-dimensional optronic encoding scheme using vortex beam is proposed.Communication is a bridge in netted radar system.The proposed scheme can effectively perform large-capacity and high-speed free-space communication,which is suitable for large-scale netted radar system.In this scheme,an algorithm with a DMD is employed to generate vortex beams that can be used for encoding.Interference is introduced to efficiently decode data information,which avoids stringent alignment required by other phase distribution based decoding technologies.This scheme enables high-dimensional encoding,such as 64-ary encoding.Owing to enhancement of encoding dimension and employment of high-speed DMDs,the proposed scheme enjoys a higher transfer rate exceeding other communication technologies.In addition,the transfer rate can be further improved by introducing vortex arrays,which makes the scheme suitable for high-speed large-capacity communication.