Estimation Method of SAR Doppler Frequency Rate Based on FrFT

• Format: Article
• Language: zho
• Published: The Northwestern Polytechnical University 2020-12-01
• Series: Xibei Gongye Daxue Xuebao
• Subjects: doppler frequency rate; frft; sar; dechirp
• Online Access: https://www.jnwpu.org/articles/jnwpu/full_html/2020/06/jnwpu2020386p1352/jnwpu2020386p1352.html

Due to the problem that the existing Doppler frequency rate estimation method is limited by the estimation accuracy, a novel estimation method of Doppler frequency rate is proposed. The present method searches the frequency rate according to the characteristic of the chirp signal in the FrFT domain. Firstly, dechirp is performed on several strong scattering points extracted from the data domain after pulse compression, and a frequency domain focused image is obtained after FFT. Then the maximum point of each distance unit is extracted. The energy of the maximum point is selected by using the window processing. After that, IFFT is performed and the dechirp conjugate reference function is multiplied by using the selected points. FrFT is performed according to the preset orders. The entropy is used to evaluate whether the order of FRFT is optimal or not. The Doppler frequency rate is calculated by using the optimal order. The simulation and real data are processed and analyzed. The present method can estimate the Doppler frequency rate accurately. A well-focused SAR image is obtained after azimuth matching filtering.