Research Of Phase Modulated Continuous Wave Inverse Synthetic Aperture Ladar

Inverse synthetic aperture ladar,which uses laser as active detection source and synthetic aperture technique to improves the resolution limitied by diffraction,in theory,can image maneuvering target in great distance with centimetre-level resolution.Because of the limitation of laser technology,the traditional system of synthetic aperture ladar in which signal is pulsed and linear frequency modulated can not satisfy the real-time working request and have random initial phase for each pulse causing imaging result blur.Therefore,this paper research the basis theory,the system realization and imaging algrithom of phase modulated continuous wave inverse synthetic aperture ladar,which can dectect target at real-time and solve the problem of random initial phase caused by plused signal.The work in this paper was around phase modulated continuous wave inverse synthetic aperture ladar.Fitstly,the mathematical model and imaging theory of inverse synthetic aperture ladar was explained.Reasons,advantages and disadvantages of the maxium length sequence coded binary phase shift keying continuous wave which is concrete realizable design for phase modulated continuous wave inverse synthetic aperture ladar were discussed in system level.After the mathematical module of system was given out,a new imaging algorithm which can compensate the phase shift caused by Doppler effect in one maxium length sequence period was introduced.Following that,key devices and parameter designing of the system were introduced.An Experimental equipment based on the new method used inside the laboratory was also introduced.Then,imaging experiments for rotation targets with more than 33.5m distance were shown.The imaging results prove the feasibility of the system and the correction of the theory.Motion compensation for maneuvering target was studied to improve the system imaging ability.A new way which deletes the unmatched points to align range cells was proposed.At last,to deal with mass data,dual compression based on compressed sensing and lossless data compressiont was proposed.With real experiment data,compression,recover and imaging result based on the recover data were exhibited.The paper has following innovation points:(1)Based on the real time working request,maxium length sequence coded binary phase shift keying continuous wave was selected as the concrete way to realize inverse synthetic aperture ladar.An experimental equipment used inside the laboratory based on the new method was designed and realized.Rotation targets were imaged with the equipment and corresponding results were shown.(2)Because of the differences between maxium length sequence coded binary phase shift keying continuous wave and the traditional way,two new algorithms were proposed.One is an imaging algorithm,whose range compression was done in segmental frequency domain.It can compensate the phase error caused by Doppler effect in one maxium length sequence period.The other algorithm is about moton compensation,which is to align range cells.Its computation cost was much less than the traditional way.