SAR Image Transform Based on Amplitude and Frequency Shifting Joint Modulation

A synthetic aperture radar (SAR) image transform method is proposed based on random period amplitude and frequency shifting joint modulation. The random period amplitude sequence is designed to modulate the radar pulse signal so that the sidelobe of range profile is disordered with high level. Based on the spectrum property of random period amplitude sequence, the frequency shifting value can be obtained to conduct the joint modulation. Subsequently, frequency shifting is applied to move the high-level sidelobe of range profile to the position of the target of interest (TOI). As a result, the TOI can be protected and a false target image emerges, which shows both blanket and deception properties. By utilizing the joint modulation in fast time and amplitude modulation in slow time, the image of TOI is covered after SAR imaging. At the same time, the false images are generated in the range and azimuth directions. Finally, simulations and SAR data experiments are conducted to obtain the transformed SAR image with proper amplitude sequence and frequency shifting parameters. The correlation coefficient between the transformed image and the real target image is calculated, which indicates the validity of the proposed method.