Algorithmes STAP récursifs sur la distance pour radar aéroporté en configuration non latérale - Range recursive STAP algorithms for airborne radar in non side looking configuration

Algorithmes STAP récursifs sur la distance pour radar aéroporté en configuration non latérale

Range recursive STAP algorithms for airborne radar in non side looking configuration

Sophie Beau Sylvie Marcos 

Laboratoire des Signaux et systèmes, CNRS, Supelec, 3, rue Joliot-Curie 91192 Gif sur Yvette Cedex

Corresponding Author Email: 
sophie.beau@lss.supelec.fr
Page: 
265-277
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Received: 
7 February 2008
| |
Accepted: 
N/A
| | Citation

OPEN ACCESS

Abstract: 

We address the problem of detecting slow moving target within ground clutter with a non side looking monostatic airborne radar using either a uniformly spaced and linear antenna (ULA) or a uniformly curved or circular antenna (UCuA and UCA respectively). To obtain the optimal STAP filter, the space time covariance matrix has to be inverted [1]. In practice, it is unknown and has to be estimated. With a monostatic radar using an ULA in side looking configuration, the clutter has specific properties : the space-time repartition of the clutter spectral power which is called “Clutter Ridge’’ is range independent. The space-time snapshots are thus iid and the classical SMI (Sample Matrix Inversion) estimator can be used [1]. But in case of a monostatic radar using an ULA in a non side looking configuration or using a UcuA or a UCA, the clutter properties are changed. The clutter ridges are range dependent and specific methods must be applied to compensate the range dependency [4], [5], [6]. But these methods are computational expensive and/or require the knowledge of the radar parameters. In this paper, we are rather interested in range-recursive subspace-based algorithms of linear computational cost. First, we establish the range dependency of the model of the clutter ridges when using ULA, UCuA and UCA in a non side looking configuration. We then present the various algorithms which are investigated. Some are based on a quadratic cost function: PAST[10], OPAST[11], API[12] and FAPI[12] algorithms, whereas another is based on a non quadratic cost function: NIC algorithm [13]. They were initially used in array processing. We here show the capability of these recursive algorithms to track the range non stationarity of the data without the use of compensation methods. We compare them to the optimal STAP filter and to the SMI and DBU algorithms in term of SINR loss. Simulations exhibit the high performance of the proposed approach to track the range non stationarity implied as well by the geometry of the antenna array as by the configuration of the radar: we here investigate both side looking and non side looking configurations. Contrary to the DBU algorithm, the range recursive algorithms converge with a short set of training data (2NM range cells are sufficient whereas DBU requires 4NM range cells).

Résumé

Cet article traite de la détection de cibles mobiles sur fond de fouillis dans le cadre de radar aéroporté monostatique utilisant trois formes d’antennes: linéaire uniforme (ALU); courbée uniforme (ACoU) et circulaire uniforme (ACU), en visée non latérale. Le traitement STAP classique, tel que la méthode SMI (Sample Matrix Inversion) ou tel que les méthodes de type eigencanceler, nécessitent une estimation de la matrice de covariance des interférences plus bruit en moyennant les données provenant des cases distances secondaires. Outre le fait que ces méthodes sont très coûteuses en calculs, leurs performances ne sont pas optimales (l’estimateur de la matrice de covariance des interférences plus bruit est biaisé) dans le cas où les données ne sont pas iid. C’est le cas, par exemple, pour les radars utilisant une ALU en visée non latérale et ceux utilisant une ACoU ou ACU. En effet, dans ces configurations, la densité spectrale du fouillis présente une dépendance en distance qui introduit une non stationnarité des données. Notre but ici est de mettre en valeur la capacité de poursuite de cette non-stationnarité en distance par des algorithmes récursifs à complexité calculatoire linéaire et ce, sans utilisation de méthodes de compensation qui s’avèrent coûteuses en temps de calcul et/ou nécessitent la connaissance des paramètres du radar.

Keywords: 

STAP, recursive algorithms, airborne radar, non side looking configuration, range dependent clutter

Mots clés

Techniques STAP, algorithmes récursifs, radar aéroporté, configuration non latérale, fouillis non stationnaire en distance

1. Introduction
2. Modélisation Des Signaux
3. Traitement STAP Et Méthodes De Compensation Classiques
4. Algorithmes Récursifs Sur La Distance
5. Résultats Obtenus
6. Conclusion
  References

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