Adaptive radar detection of point-like and distributed targets embedded in Gaussian or non-Gaussian disturbance is an issue that has gained increasing attention among radar engineers during the last few decades.
Most of the quoted decision schemes, when applied in real situation, exhibit the following two drawbacks. The first disadvantage is that they may experience performance degradation, when the actual steering vector is not perfectly aligned with the nominal one, owing to the fact that they suppose the exact knowledge of the signal array response vector. Several causes can yield signal mismatches, for example, calibration and pointing errors, wavefront distortions and imperfect antenna shape. The other one is that they may be quite sensitive to a sidelobe signal, namely a possible waveform impinging from a particular direction may determine detection whereas the radar beam is pointing elsewhere. For example, a strong target may trigger detection when it is located in the antenna sidelobes and be perceived as a weaker target in the main beam.
Scientists in the field of acoustics from home and abroad focus on the design selective detectors for distributed targets in the presence of homogeneous and partially homogeneous Gaussian disturbance with unknown covariance matrix.
Detection of distributed targets and devise adaptive receivers capable of rejecting signals orthogonal to the useful search direction in the “quasi-whitened” space is paid attention to.
This research distinguishes from previous ones in several respects. Its main novelty stems from the fact that it contains the derivation of the plain GLRT assuming the ABORT idea for homogeneous and partially homogeneous environment. They also devise an ad hoc detector resorting to the two-step GLRT-based design procedure for partially homogeneous environment and show that it coincides with the generalized adaptive subspace detector (GASD).
Finally, the study contains a performance assessment, carried out with simulated data, showing that the new tests exhibit well rejection capabilities of sidelobe signals. This result is very desirable since it allows for a very selective discrimination of signals entering in the radar antenna sidelobes.
Moreover, it suggests the use of proposed receivers in a two-stage configuration. That is, detection structures formed by two detectors: a first stage with poor selectivity properties and a second stage much more selective to discriminate whether or not detected signals are to be considered useful target echoes. In the light of previous considerations, the proposed solutions might be good candidates for the second stage of detection.
This research result was published on the recently issued IET Radar, Sonar and Navigation (Vol. 6, No. 6, Pages 483–493, 2012).