Satellite-ground bistatic SAR (synthetic aperture radar) time-frequency synchronization method based on navigation satellite

Abstract

The invention relates to a satellite-ground bistatic SAR (synthetic aperture radar) time-frequency synchronization method based on a navigation satellite, and belongs to the technical field of radar signal processing. The time-frequency synchronization of a satellite-ground bistatic SAR system can be realized without a post-event ephemeris. A parameter estimation method provided by the invention can be used for extracting navigation message information by virtue of direct waves, decoding acquisition time and satellite orbit information to calculate a theoretical time delay history and a theoretical Doppler phase history corresponding to received data, and subtracting the theoretical time delay history and the theoretical Doppler phase history from an apparent time delay history and an apparent Doppler phase history to obtain synchronous error estimation values of time and phase. According to the method, the real-time property of imaging can be improved, the time information can be accurately acquired, and the error influence caused by time deviation is lowered. The method is suitable for all navigation satellites and is wide in application range.

Description

Technical field [0001] The invention relates to a satellite-to-ground bistatic synthetic aperture radar (SAR) time-frequency synchronization method based on navigation satellites, and belongs to the technical field of radar signal processing. Background technique [0002] The satellite-to-ground bistatic SAR technology based on navigation satellites is a way to achieve continuous ground observation. Its system realizes range resolution by transmitting signals with a certain bandwidth, and realizes azimuth resolution by forming an effective rotation angle to the target through satellite flight. Combined with the characteristics of the large number of navigation satellites and short revisit time, it can achieve continuous two-stage scenes. The effect of dimensional imaging. [0003] However, the satellite-to-ground bistatic SAR system based on navigation satellites has time and frequency synchronization errors in the received signals due to separate transceivers. Under the condition...

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Problems solved by technology

[0003] However, the satellite-ground bistatic SAR system based on navigation satellites has time and frequency synchronization errors in the received signal due to the separation of transceivers. Under the condition of long synthetic aperture time, the time-varying time and frequency synchronization errors will lead to severe defocusing of the image.

However, the traditional synchronization method estimates and compensates the synchronization error by using the direct wave signal and the post-event ephemeris, which cannot meet the requirements of real-time synchronization, because the post-event ephemeris cannot be obtained immediately, and there is no post-event ephemeris for Beidou navigation satellites. Moreover, the traditional method cannot obtain the accurate UTC time corresponding to the echo data, which will limit the application of the traditional synchronization method and deteriorate the performance of its synchronization processing

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