A new estimation method for SAR frequency difference drift base on frequency band synthesis

To improve the range resolution of stepped-frequency SAR system, frequency difference drift should be estimated using the raw data as accurately as possible. This paper proposes a new method to estimate the accurate frequency difference drift base on frequency band synthesis. In this method, the echoes of different subband signals will be compressed firstly so as to find out point targets with strong energy. Secondly, two phase functions are constructed by a pre-set frequency difference and multiplied to the echo signals of corresponding subband respectively; the interferometry phases are then obtained from the shifted subband signals. Finally a new normalized signal vector can be constructed from the interferometry phases; and the accurate frequency difference drift can be obtained by performing FFT to the vector. The required accuracy and the implementation strategies of this method are discussed, and the effectiveness and accuracy of this method are shown by some real SAR data results.