Research On Diving Missile-borne Synthetic Aperture Radar Imaging Algorithm With High-resolution

Synthetic Aperture Radar(SAR)creates a larger virtual aperture by using of relative motion between the platform to the targets.Within the virtual aperture,it realizes the high-resolution and two-dimensional imaginary for a scene by coherently integrating the echo.It has been widely adopted in the fields of both military and civilian because it can produce high-resolution and multi-dimension images of desired scene observation at any time of day and night regardless of weather conditions.One of the research focuses is the high-resolution missile-born SAR imaginary,which is conducted by combining the SAR with the high-speed platform such as missile.In order to meet the demands of flexible observation,computational load decrease and efficient imaging,missile-born SAR usually works on a highly-squinted mode with sub-aperture data processing method.However,in the diving condition with a high squint,the echo suffers dramatically range-azimuth coupling due to the 3-dimensional(3D)velocity and acceleration,meanwhile,the range-dependent squint angle makes the range envelop and Doppler phase 2-dimensional(2D)spatial variant,which makes the conventional algorithms for straight-path not applicable.Thus,it is well worth to explore an effective algorithm for missile borne SAR working in diving model with high resolution.According to the problems mentioned above,this paper focuses on three aspects,which are developed as follows:1)A three-dimensional equivalent spherical analytical model was studied in this paper.In order to completely remove the linear range cell migration(LRCM),this paper adopts the LRCM correction(LRCM),acceleration compensation(AC)and keystone transformation in the range preprocessing.After the Bulk RCMC(BRCMC),this paper constructs the model through the analysis on the 2D spatial variance of the echo,which can be used to describe the spatial variance of the beam center slant range and Doppler phases with a higher accuracy.The simulation validates the effectiveness of the proposed model.2)An azimuth spatial-variant envelope correction method is studied.Based on the equivalent spherical analytical model proposed in 1),the space-variant expressions of RCMs are re-deduced.According to the analysis on the residual high-order RCM,this paper proposed an azimuth spatial-variant envelope correction method to achieves the residual high-order RCM correction,which produces high quality range compression and shows high potential for the range processing of the echo of missile borne with diving and highly squinted model.The simulation result validated the effectiveness of the proposed method.3)An azimuth-variant Doppler phases correction method is studied.In order to the deal with the case of spatial variant Doppler phases,this paper remodel the azimuth-dependence of the Doppler phases based on the proposed equivalent spherical analytical model,following which a frequency extended non-linear chirp scaling,(FENLCS)algorithm combined with sub-aperture is proposed.This method not only corrects the quadratic and the cubic azimuth-dependent Doppler phases,but also takes the azimuth-dependent residual centroid into account.The simulation result validated the effectiveness of the proposed method.