Improved Interference Rejection Using Multi-Static Radar Signal Processing

Monday, February 01 2010

In multi-static radar (MSR), the transmit/ receive aperture is divided into a number of sub-apertures that can be placed in various locations relative to each other. These locations can be chosen to optimize the performance of the radar in terms of some specific task. Two multi-static approaches have been investigated:

• Closely spaced apertures – distributed aperture radar (DAR)
  
• Widely spaced apertures

Realizing the greater capability of MSRs requires unique waveform and signal processing approaches. A computer simulation has been developed that permits the analysis of MSR signal processing.

Multi-static radars, in a distributed aperture mode, can potentially provide significantly improved target tracking because of the large baseline between the various apertures. The resulting angular resolution can be orders of magnitude better than the resolution of a monolithic system (single large radar). This capability comes with a cost because of the resulting grating lobes (multi-statics with evenly spaced apertures) or high sidelobes (multi-statics with randomly spaced apertures).

The same angular resolution can provide improved electronic protection (EP) capability. For a single-aperture radar, jammers located near targets of interest cannot be nulled without impacting the antenna mainbeam and therefore, the target returns. But the multi-static system, with its very-longbaseline receive aperture gain on the target can be maintained while a deep null is placed in the direction of the jammer.

Imaging and Discrimination

Two-dimensional images of moving targets can be obtained through inverse synthetic aperture radar (ISAR) processing. The range and cross-range dimensions of radars viewing the target from widely separated angles will achieve target- centered resolution in different dimensions. For example, two radars independently viewing an object in its plane of motion (linear, rotating) with 90º of separation will provide complementary information: the range resolution of one radar will be the cross-range resolution of the other, and vice versa.

Coherent fusion processing of the data from these two radars can provide improved resolution. Fusion of the data from the bi-static path can further improve the resolution. Also, two or more radars viewing an object from different angles not in its plane of motion can provide three-dimensional images. The overall 3D resolution of the object will be a function of the range and crossrange resolution of the individual radars and their angle separation as viewed from the target location.