Research Of R-D And ωK Algorithm For Frequency Modulated Continuous Wave SAR Imaging

In the field of airborne earth observation, there is special attention for compact, costeffective, high resolution imaging sensors. Mini-UAV has reached a high degree of maturityand could provide the conditions for this implementation; however, due to the limit of thepayload, it is not suitable for installing traditional pulse synthetic aperture radar, which iscomplex and bulky. The highly miniaturized FM-CW SAR system, which combines FMCWtechniques with SAR technology, could satisfy the requirement of cost-effective developmenttrend and it is small enough to be mounted on such MUAV system. As for a kind ofsmall-scale remote sensing imaging methods, FMCW-SAR will play an important role ondisaster monitoring, measuring ocean internal wave imaging as well as highway monitoring.Due to the fact that the FMCW-SAR is continuously transmitting signals while platformmoving, the "stop-and-go" approximation which is used for the derivation ofconventional SAR algorithms could not valid. So it is necessary to analyze specific algorithmsfor FMCW SAR.FMCW-SAR is typically used on a UAV platform, therefore, it is very important to studythe real-time image processing algorithm. Range-Doppler (R-D) algorithm is the most simpleand classic SAR imaging signal processing algorithms, nevertheless, the algorithm usuallyrequires interpolation operation. Currently, the modified R-D algorithm avoids theinterpolation operation, but not fully utilize the characteristics of FM signals to simplify thecomputational complexity. To solve this problem, we propose the novel R-D algorithm, whichis suitable for FMCW-SAR. Finally through the analysis of calculated amount and thesimulation results, we could find that the proposed algorithm is more suitable for real-timeimaging, and verify the validity of the novel algorithm.Spotlight mode is an important means to achieve high-resolution imaging for FrequencyModulated Continuous Wave SAR. Due to the effects of the continuous motion of the radarplatform, Spotlight echo Doppler bandwidth much larger than the strip of SAR, therefore,spotlight FMCW-SAR cannot be focused on azimuth. As one of the most accurate imagingalgorithms,ωKalgorithm is often used in spotlight mode for pulse SAR. This dissertationproposed a new processing algorithm for spotlight FMCW-SAR is presented using the K algorithm for the first time. Simulation results show that the novel method could figure outthe range migration problem induced by the motion within the sweep of FMCW-SAR, andcould make the azimuth direction’s energy focus on very well.