Advanced Signal Processing to Enhance Target Detection & Discrimination In High Countermeasure Environment

ABSTRACT: Missile defense radars use wideband waveforms along with coherent processing to extract detailed target features and perform high range /Doppler resolution functions. Reduced RCS targets embedded in high clutter (chaff, or chaff-like fuel debris, etc.) environments present significant challenges. Closely spaced objects and decoys accompanying targets of interest inherently increase the complexity of the problem. Additionally, other forms of electronic countermeasures can also reduce the defense ability to detect, track, and discriminate such reduced RCS threat. These factors place demanding signal and data processing requirements on the sensor and may require advanced algorithms and architectures. To counter this problem, dB Research proposes an advanced signal process¬ing technique to perform high resolution detection and imaging. This technique is based on utilizing a three-dimen¬sional signal model that utilizes a third order Taylor series expansion about incremental, time, azimuth angle, and elevation angle. In this case, once a location of interest (where potential targets embedded in high clutter environ¬ment) has been identified by the radar, a burst of wideband waveform is used. The required signal processing includes heterodyning with respect to a fictitious scatters located at the center of the wideband cell of interest. Then spatial FFTs are used to extract target angular information. This way the problem of wideband target detection is transformed into a spectral analysis problem. The resultant angular (azimuth and elevation) resolution cells for a given range cell (time) is proportional to the spectral resolution of the spatial FFTs and is typically order of magnitude smaller that when using typical wideband waveforms and processing techniques. For example, an area of about 2x2 meter can be spectrally divided into a 128x128 cells. This way, much less clutter RCS would compete with the reduced target RCS, thus facilitating detection. Additionally, if coherent integration is used, then Doppler imaging can be accom¬plished where target's scatterer centers coherently integrate while other closely spaced objects would decorrelate.