Performance Analysis of Space-Time Array Processing Using Ultrawideband-Throb Signals for High-Resolution Imaging

In this paper, performance analysis is conducted to demonstrate that the combination of employing ultrawideband (UWB) throb signals and array beamforming can enhance the resolution performance as well as the robustness of imaging radar systems, i.e., airborne and spaceborne synthetic aperture radar. A mathematical model for the response of an array beamforming system, with systematic faults and channel instability, to received UWB-throb signals is derived. The effect of parametric random errors associated with this array beamforming system on the processing gain is analyzed for the UWB-throb signal and the linear FM chirp signal. Space-time resolution function, an essential tool for waveform design, is derived for the UWB-throb signal corrupted by parametric random errors. By using the Monte Carlo computer simulation technique, plots are generated for the space-time resolution function, temporal profile, array factor, and energy beampattern, for different values of the signals' design parameters and the statistical parameters of the random errors. The plots reveal the degradations in the beamforming performance due to the presence of parametric random errors, i.e., drop in the central peak amplitude, rise of sidelobe level, generation of spurious sidelobes, and beam-shape loss affecting beamwidth and beam-pointing accuracy. In the presence of parametric random errors, the robustness of array beamforming using the UWB-throb signal is superior to that achievable by array beamforming using the linear-FM chirp signal. The resolution angle obtained from the energy pattern of the UWB-throb signal provides a tradeoff between signal design parameters and array size for improving the angular-resolution capability. Such a tradeoff is desirable in practice to achieve a balance between system complexity and cost effectiveness.