Sparse Array Antennas and Clutter Suppression Processing for Space-Based Radars
Rept. for Jun 1999-Jun 2000
AIR FORCE RESEARCH LAB ROME NY SENSORSDIRECTORATE
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Future intelligence, surveillance, and reconnaissance ISR missions for the US Air Force are expected to require data from space-based radar SBR systems. Several types of data will be needed, including ground-moving target indicator GMTI and airborne-moving-target indicator AMTI data. SBR design concepts that are best able to provide these different types of data are still evolving. Space-array antennas and special signal processing techniques are shown here to be capable of achieving useful performance for both GMTI and AMTl applications. Sparse-array patterns for elements at arbitrary but known positions are computed by summing the complex vector fields that are functions of the path length difference of each element from the center of the array for azimuth and elevation steer directions of interest. The narrow beamwidths achievable with sparse arrays do not change the clutter power-spectral-density Cpsd significantly because the reduced clutter power from each range-azimuth resolution cell is offset by the correspondingly smaller Doppler spread in the cell. Thus the minimum detectable velocity MDV of the moving target is controlled mostly by the pattern of the sub-arrays that are used as elements for the receiving array. For this reason, additional space-time adaptive processing STAP must be performed to achieve operationally useful GMTI and AMTI results. A new technique, called main-beam phase compensated aperture MPCA processing, is described and evaluated in this paper. When combined with the beamforming processing associated with a phased-array antenna in any configuration, MPCA is shown to result in estimates of SBR performance that are very promising.
- Active and Passive Radar Detection and Equipment
- Unmanned Spacecraft