An improved scheme of Digital Beam-Forming in elevation for spaceborne SAR

In the high-resolution, wide-swath imaging application of spaceborne synthetic aperture radar (SAR), Digital Beam-Forming (DBF) technique can be employed to receive and handle echo data with multiple channels in elevation, for the purpose of increasing the receive gain and Signal-to-Noise Ratio (SNR). According to the geometric relationship among these channels, this paper analyzes the impulse response function of arbitrary elevation channel, and derives its explicit expression. Based upon this, an improved DBF processing scheme, which combines the time-variant weighting and Finite Impulse Response (FIR) filtering, is presented. Additionally, the block diagram of this DBF configuration is given. Compared with other echo-receiving methods, this approach can maximize the receive gain and optimize the system performance for the case of long pulse, without much increase of the system complexity. Simulation results indicate that it enables the system to achieve its theoretically optimal receiving performance.