Study On Imagine Agorithems For Space-missile Borne Bistatic Synthetic Aperture Radar

As a special bistatic configuration,space-missile borne bistatic synthetic aperture radar(SMB-BiSAR)has a receiver installed on the missile close to the battlefield,and a transmitter plated on the satellite far from the battlefield.SMB-BiSAR can combine the advantages of the large coverage and high security of the space-borne SAR with the high resolution and high maneuverability of the missile-borne SAR to achieve unique space-to-missile cooperative detection,guidance,etc.,which has a good application prospect.SMB-BiSAR has unique advantages at the cost of system complexity.Satellite orbit differences leads to major changes in the geometric model of SMB-BiSAR,and maneuvering of missiles leads to the failure of traditional models and the mismatch of algorithms.Based on the geometric configuration of the SMB-BiSAR,this thesis conducts in-depth theoretical analysis and simulation verification of the two-dimensional resolution,echo characteristics,and imaging algorithms of the model.As a special bistatic configuration,the imaging model of SMB-BiSAR is constructed in vector according to the geometry of satellite and missile in the reference target loca1(RTL)and earth center fixed(ECF)coordinate system firstly.And the range history and echo signal model is obtained.Then,the constraint of the missile flight path is analyzed based on the orthogonality of iso-range and iso-Doppler contours.Finally,the spatial resolution expression of SMB-BiSAR is derived by the gradient of range history and Doppler frequency.The simulations verify that SMB-BiSAR has the ability to obtain the high-resolution image of target area in the case of large squint angle and forward-looking by the path planning of missile.Considering the imaging geometry configuration of SMB-BiSAR will be more complicated,since the synthetic aperture time of missile is shorter than the synthetic aperture time of satellite,the motion of satellite can be ignored in the shorter synthetic aperture time.When the transmitter is stationary,the range history can be simplified into a single root number.The large three-dimensional velocity of motion and the acceleration will cause the azimuth space variance of the imaging result to be seriously defocused.And an azimuth time resampling method is introduced to process the azimuth space variance,by which an echo signal with traditional hyperbolic model range equation can be obtained,which is similar to the traditional bistatic SAR case.Based on the simplified range equation,the typical imaging algorithms such as range-Doppler and omega-k algorithms are improved.After targeted optimized compression processing,two-dimensional imaging is realized.Simulations are finally performed to verify that the proposed method is suitable for the imaging of SMB-BiSAR.