Richard Klemm

Tracking of ground targets with bistatic airborne radar

Detection of moving targets in stationary clutter can be accomplished by STAP radar. In contrast to monostatic radar the performance of bistatic STAP depends strongly on the actual radar-target geometry. Even for sidelooking radar the clutter Doppler is generally range dependent which causes special problems in estimating the space-time clutter covariance matrix. For certain bistatic constellations clutter notches as appearing during track (i.e. areas of low probability of detection) may be considerably wider than in monostatic radar. The bistatic transmitter-receiver constellation has strong implications on ground moving target tracking, which is basic for producing a recognized ground picture as well as for analyzing traffic flows, identifying sources and sinks of traffic, or detecting lines of communication. Aspects of a bistatic GMTI tracking algorithm are described and some typical tracking results are given. Special emphasis is placed on a suitable modeling of the bistatic radar characteristics within the tracker.

Adaptive monopluse with STAP

Monopulse is a well known technique for high accuracy estimation of target parameters such as azimuth and elevation as well as the radial velocity. In conjunction with an adaptive processor for cancellation of interference one obtains so called adaptive monopulse. Interference may be either jamming or clutter or both. In this contribution some properties of adaptive monopulse applied in a clutter environment is discussed. We focus on an airborne radar scenario so that the adaptive monopulse includes a space-time adaptive processor (STAP). Several different STAP architectures are compared with respect to their aptitude for target parameter estimation

Tracking of multiple ground targets with adaptive monopulse radar. Part I: The sensor

In this contribution and in companion paper [1] aspects of ground target tracking by means of airborne radar are discussed. The radar sensor consists of a multichannel array antenna enabling space-time adaptive processing (STAP) for clutter rejection, and angle and Doppler monopulse estimation. Both the STAP and adaptive monopulse algorithms are described and the aptitude for monopulse estimation with different processor architectures is discussed. Results for a typical multiple-target scenario are presented.

High-resolution wide-swath SAR

This chapter presents the principle of high-resolution wide-swath synthetic aperture radar (SAR), a means for imaging wide areas at high resolution. The material covers the limitations of achieving wide-swath and high-resolution with a traditional SAR, the basic idea of using a multi-aperture SAR to overcome this limitation and current implementations where multi-aperture (or multiple antenna) systems collect data in an ideal configuration. Overviews of approaches to processing data collected in nonideal configurations, such as when the data are collected with non-uniform sampling and/or when they are collected with a squinted system, are then introduced. Armed with an overview, the chapter introduces the theory of multi-aperture SAR processing with the objective of generalizing the concept of high-resolution wide-swath to higher resolution, wider-swath SAR. This enables application of the added degrees of freedom to other modes such as spotlight and high-resolution stripmap. In order to present the theory and the generalizations, and in consideration of possible future systems, the theory is derived in the wavenumber domain for wideband and/or widebeam, space-based systems with special cases for narrowband systems presented as appropriate. In contrast to much of the current literature, the theory views the antenna patterns as the key provider of the additional degrees of freedom and proposes to utilize other pattern characteristics in addition to the phase-centre separation to improve imaging. For this reason, special care is taken in developing the antenna pattern dependence in the signal model. The approach for signal reconstruction focuses, mainly, on the minimum mean-square error method as it is quite general and includes, as special cases, the well-known projection approach as well as the space-time adaptive processing (STAP) approach. Further, it inherently, simultaneously improves the geometrical and radiometrical resolution due to favourable weighting by the antenna pattern and a less aggressive ambiguity prescription as compared to other techniques. The approach also naturally incorporates other more generalized system configurations where, for instance, the antenna patterns have, not only different phase-centres, but also different shapes or different pointing directions. As an added feature, the presented method is robust against matrix inversion problems which can render the projection approach intractable. The special case of a phased-array multi-aperture system is presented.

Festzielunterdrückungsfilter für bewegte Sensorgruppen - Auswirkungen suboptimaler Abtastung

Die Aufgabe, von bewegten Plattformen aus mit einer Sensorgruppe bewegte Ziele vor dem feststehenden Hintergrund zu entdecken, fuhrt zu folgendem Problem: Eine lineare Sensorgruppe aus identischen und identisch ausgerichteten Einzelsensoren (Radar, Sonar) bewege sich mit konstanter Geschwindigkeit in Richtung der Array-Achse. Die Echos des unbewegten Hintergrundes uberlagern sich aus allen Richtungen und bilden nach Bewertung durch die Richtcharakteristik der Einzelsensoren die Ausgangssignale. Abhangig von der Richtung ergeben sich unterschiedliche Radialgeschwindigkeiten und damit Dopplerfrequenzen. Die Abtastwerte aus einer Entfernungszelle bilden ein zweidimensionales Feld in Raum (Sensorposition) und Zeit (Impulsnummer).