CFAR coherent radar detection against K-distributed clutter plus thermal noise

The paper shows the non CFAR characteristic of the Asymptotically Optimum Detector (AOD), when applied to a mixture of K-distributed clutter plus thermal noise, as the target Doppler frequency is varied. The upper bound to the performance: against such composite disturbance is investigated by considering an ideal-AOD detector, which assumes the knowledge of the local clutter power in the cell under test. A practical scheme is obtained by replacing the known local power value with its estimate. The resulting detection scheme, named Locally Adaptive-AOD (LA-AOD) shows a proper CFAR characteristic, but yields strong detection losses In the same Doppler frequency region where the original AOD operates effectively with CFAR. Finally, a combined detector, Comb-AOD, is proposed, which takes the benefits of both the AOD and LA-AOD structures, and its detection performance is fully characterized as clutter spikiness and correlation vary

Optimum CFAR detection against compound gaussian clutter with partially correlated texture

The paper deals with CFAR detection in compound Gaussian clutter with a partially correlated texture component. A theoretical high performance upgrade has been demonstrated using the ideal exact knowledge of this component in the CFAR scheme ('ideal CFAR') in a paper by Watts (1985) for K-distribution, For practical application the authors derive some optimum local texture estimators, based on the closest range cells, and use the estimated values to set the detection threshold. The schemes differ for operating over the intensity or the logarithm and for using or not prior information about the texture correlation. In particular, a maximum a posteriori estimator is derived, which outperforms the usual cell averaging CFAR and provides always performance close to the 'ideal CFAR'. The derivations are valid for all compound Caussian clutters. The performances obtained with K and compound weibull distribution are compared, assessing the robustness of the proposed detection scheme

A new approach to the problem of doppler resistant barker sidelobes reducing networks

Les signals codifiés par la phase sont utilisés souvent dans les modernes radar avec beaucoup de résolution; ils souffrent la présence des lobes secondaires en distance que l'on peut réduire trés difficilement, surtout parce qu'ils changent leurs positions et niveaux lorsque l'effet Doppler est présent. Ceci est important surtout lorsque deux (ou plusieurs) cibles sont proches, parce que celle-là plus-grande peut cacher, par ses lobes secondaires, l'autre. Ceci a lieu pour les radar de poursuite où il faut détecter une cible très petite proche d'une bien plus grande. Cet article décrit une solution au problème précédent qui peut être utilisée dans les radar de poursuite. La connaissance de la position de la cible poursuitée permet de mesurer la phase statique du signal interferent. Par conséquent il est possible de tourner le code comprimé: ceci signifie détecter la cible si le déplacement Doppler n'est pas présent; de toute façon l'influence de l'effet Doppler résulte grandement réduite et il est possible de réaliser un approprié circuit de réduction du niveau des lobes secondaires qui est résistant a l'effet Doppler et aussi capable ae faire dégrader très peu la rapport pic/lobes

Adaptive polarimetric target detection with coherent radar part I: Detection against Gaussian background

The derivation of a completely adaptive polarimetric coherent scheme to detect a radar target against a Gaussian background Is presented. A previously proposed Generalized Likelihood Ratio Test (GLRT) polarimetric detector Is extended to the case of a general number of channels; this exploits the polarimetric characteristics of the received radar echoes to improve the detection performance. Together with the fully adaptive scheme, a model-based detector Is derived that has a lower estimation loss. A complete theoretical expression is derived for the detection performance of both proposed polarimetric detectors. They are shown to have Constant False Alarm Rate (CFAR) when operating against Gaussian clutter, but to be sensitive to deviations from the Gaussian statistic (problem solved in Part H of this work). The application to recorded radar data demonstrates the performance improvement achievable in practice