Improved spectrum reconstruction technique based on chirp rate modulation in stepped-frequency SAR

To improve the efficiencies of the traditional spectrum reconstruction techniques, an improved spectrum reconstruction technique (ISRT) based on chirp rate modulation (CRM) is proposed. With the help of a CRM operation, a reconstructed wideband signal with a narrow pulse width can be obtained. Compared with the traditional time domain spectrum reconstruction technique (TSRT), ISRT is less time-consuming since much less samples are needed. Compared with the traditional frequency domain spectrum reconstruction technique (FSRT), the reconstructed signal is a chirp signal, which has no limitation on the subsequent imaging algorithm. What is more, processing steps of ISRT are optimized, and the computational burden is less than that of TSRT and FSRT. Both simulation results and real data processing have verified the validity of ISRT.