Swath widening and data reduction in synthetic aperture reconnaissance radar (SAR)

摘要

Until today, SAR was considerably restricted in its swath width, owing to the requirement that, for a desired geometrical resolution in the direction of flight, a minimum pulse repetition frequency had to be chosen, automatically fixing the maximum swath width previously possible. The method described here allows this swath width to be expanded n times without substantially increasing the data rate in the transmission of the SAR raw data to the ground. This is significant since, without this increase in swath width, the transmission rate of the SAR raw data is at the limit of current technology with the systems which can be realised today. The method utilises the fact that the Doppler history for targets from different distance ranges has slight differences. It allows the echoes from different distance ranges (ambiguity zones) to be temporarily interfolded and transmitted to the ground as just an echo. On the ground, this method allows the one echo to be broken down again into the echoes from the various distance ranges, it being possible to achieve a good signal-to-noise ratio.