Abstract
In high-resolution bistatic synthetic aperture radar (SAR) systems, parameter estimation is essential to moving target imaging quality. However, precise parameters are difficult to obtain without priori information due to the relative along-track and across-track velocities between the moving target and platforms that change with time. A parameter estimation and imaging approach for moving targets is proposed. First, slant range and relative velocities expression are deduced based on the geometry of bistatic SAR model with one stationary configuration. Then, range curvature term are compensated skillfully by fitting the range-compressed curve in two-dimensional time domain, meanwhile, the initial estimated range walk slope can be achieved. Finally, precise Doppler centroid is estimated through searching for the maximum contrast with folding search algorithm, which is giving consideration to both searching precision and computational complexity. Thus, the proposed algorithm provides an effective way for parameter estimation and imaging of moving target without prior information and interpolation operation. Experimental results show the effectiveness of the proposed method.
Highlights
In bistatic synthetic aperture radar (SAR) data acquisition process, beam center offset would reduce signal-to-noise ratio, increase main lobe width and change focusing position, which are caused by motion error of platforms and beam pointing error of antennas
Among the mentioned three algorithms, wavelength diversity algorithm (WDA) and Multilook cross correlation (MLCC) are suitable for low-contrast scene, and multilook beat frequency (MLBF) is propitious to high-contrast scene
Analysis of computational complexity: Assuming that the initial step error is ΔE, the computational complexity of folding search algorithm based on maximum contrast is log2ðΔE∕ΔK0Þ, while the conventional algorithm based on fixed step is ΔE∕ΔK0
Summary
In bistatic SAR data acquisition process, beam center offset would reduce signal-to-noise ratio, increase main lobe width and change focusing position, which are caused by motion error of platforms and beam pointing error of antennas. Accurate Doppler centroid estimation is the premise of high-quality moving target imaging. Multiple PRF4–6 avoids Doppler ambiguity based on a set of PRFs, whose disadvantages lie in the complexity of system design. This method is employed mostly in ScanSAR mode. Curve fitting is applied to range-compressed signal in two-dimensional (2-D) time domain. On this basis, precise Doppler center is estimated using high-efficient folding search algorithm.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
