It is a common synchronization approach of the bistatic Synthetic Aperture Radar (BiSAR) with spaceborne/stationary configuration that obtains synchronization information from a direct signal. An easy and effective synchronization method is using the direct signal as a match filter to compress the echo for range compression. This method requires a high signal-to-noise ratio (SNR) of the direct signal, because the low SNR of the direct signal affects the synchronization result. Furthermore, it affects the imaging quality and bistatic-InSAR (BiInSAR) result seriously. Two factors affect the SNR of the direct signal: low gain and saturation. The transmitter and receiver antenna beam patterns cause the received direct signal's power variance during the exposure time. The requirement of high gain and no saturation cannot be satisfied simultaneously during the exposure time when the receiver sub-system does not have automatic gain control (AGC). In this paper, a modified synchronization approach is proposed. The proposed method not only tolerates the low gain and saturation, but also does not require the parameters of the transmitted signal, such as FM chirp rate, bandwidth and transmitted pulse length. The proposed method makes the gain design of the synchronization channel easy. The experiment results verifies the effectiveness of the proposed approach.
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