Principles of SpaceTime Adaptive Processing (3rd Edition)
This book presents a systematic introduction to airborne MTI (moving target indication) system design for use in the fields of earth observation, surveillance and reconnaissance, with particular regard to the suppression of clutter returns. New developments in the field and special aspects of airborne MTI radar are included and make this book the definitive text on the principles of STAP.
Inspec keywords: synthetic aperture radar; spacetime adaptive processing; sonar; phased array radar; radar clutter; airborne radar; interference suppression; spaceborne radar
Other keywords: signal processing; earth observation; surveillance; clutter suppression; airborne phased array radar; spacebased MTI radar; clutter models; array processing; bistatic radar configurations; spacebased phased array radar; antijamming technique; ISAR; bandwidth effects; nonlinear antenna arrays; moving target detection; reconnaissance; sonar; spacetime adaptive processing
Subjects: Radar equipment, systems and applications; Signal processing and detection; Radar theory; Electromagnetic compatibility and interference
 Book DOI: 10.1049/PBRA021E
 Chapter DOI: 10.1049/PBRA021E
 ISBN: 9780863415661
 eISBN: 9780863419942
 Page count: 672
 Format: PDF

Front Matter
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1 Introduction
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Airborne MTI radar the major part of this book is focused on this subject. Some of the other aspects, however, will be touched on in later chapters. Chapter 1 deals with an introduction into the problems of MTI processing, including the effect of radar platform motion. Reference is made to various authors who contributed to this field. The signal processing tools as required in subsequent chapters are briefly described.

2 Signal and interference models
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In this chapter models for target, clutter, jammers and noise are derived which form the basis for the numerical evaluations carried out in the subsequent chapters. To some extent we follow the derivation by VAN TREES [662, pp. 238].

3 Properties of airborne clutter
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In this chapter some basic properties of airborne clutter are analysed. These include spaceDoppler characteristics, the spacetime covariance matrix and the associated azimuthDoppler.

4 Fully adaptive spacetime processors
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In this chapter we focus on two spacetime processors which are fully adaptive. 'Fully' adaptive means that the number of degrees of freedom as given by the number of array elements and echo pulses will be preserved in the clutter rejection process. 'Adaptive' means that clutter suppression is based in some way on the received clutter data, for instance on an estimate of the clutter covariance matrix.

5 Spacetime subspace techniques
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Spacetime transform processors basically offer a possibility of clutter suppression in a reduced signal vector space. They are based on a linear transform whose columns are spacetime vectors. One of these vectors is a signal matched search channel while the others serve as clutter reference channels.

6 Spatial transforms for linear arrays
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It was pointed out in Chapter 5 that linear spacetime transforms can be used to reduce the signal vector space down to the clutter subspace which leads to a reduction of the computational expense in the processing. However, we noticed a dependency between the required number of degrees of freedom of the processor and the dimension of the signal vector space (number of antenna elements N, echo sample size M). Therefore, these techniques are useful mainly for small antenna arrays and small echo sample size. It was found furthermore that such systems may suffer from a lack of degrees of freedom in the case of additional eigenvalues due to bandwidth effects or channel errors. In this chapter we analyse the effect of spatial transforms in the context of space time adaptive MTI filters. Such transforms have been widely used in adaptive jammer nulling. One prominent example is the sidelobe canceller.

7 Adaptive spacetime digital filters
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In this chapter we investigate the use of digital filters for space time clutter suppression. In this way we try to reduce the signal vector space in the temporal dimension.

8 Antenna related aspects
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In this chapter some antenna specific aspects are discussed. Chapter 6 dealt in some detail with spatial transforms to reduce the signal vector space in the spatial dimension. Some specific properties of linear arrays were identified. It was shown how to use identical subarrays to reduce the number of antenna channels in order to reduce the number of degrees of freedom of the spacetime processor. The concept of overlapping subarrays led directly to the concept of symmetric auxiliary channels. Planar array configurations for nearoptimum spacetime MTI processing were derived. In this chapter we try to find out how these or similar techniques can be applied to realistic (also nonlinear) antenna arrays.

9 Spacefrequency processing
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In this chapter some consideration on spacefrequency domain processing are made. We discuss a total of five different processing schemes. Wright and Wells compare preDoppler and postDoppler architectures for application with spacebased radar. Kealey and Flnley as well as Blckert compared pre and postDoppler STAP on the basis of airborne clutter data. They found both approaches equivalent.

10 Radar ambiguities
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A pulse Doppler radar can be ambiguous in either range or Doppler frequency. The ambiguity of a radar depends on the selected pulse repetition frequency (PRF). Three modes of airborne radar operation are well known: the high PRF (HPRF), medium PRF (MPRF), and low PRF (LPRF) mode. In this chapter, range ambiguities and Doppler ambiguities, were discussed.

11 STAP under jamming conditions
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In this chapter the effect of additional jamming on the performance of clutter filters will be analysed. We assume that the jammers transmit continuously (CW) and are broadband, that is, the jammer bandwidth is larger than the usable Doppler bandwidth.

12 Spacetime processing for bistatic radar
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In this chapter the impact of bistatic radar operation on the performance of air/spaceborne MTI radar based on spacetime adaptive processing is discussed.

13 Interrelated problems in SAR and ISAR
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In this chapter we discuss two specific problems of spacetime adaptive processing for SAR and ISAR. The first problem is strongly related to clutter suppression as has been treated in previous chapters. The question to be answered is how far inverse synthetic aperture (ISAR) imaging of moving targets by a moving phased array radar is degraded by spacetime clutter filtering. ISAR techniques exploit the target motion rather than the radar platform motion for imaging of moving targets. Details of the principles of ISAR can be found in WEHNER [701, pp. 341].

14 Target parameter estimation
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The major part of this book is concerned with the detection of slow moving targets by a moving radar. Specifically, the suppression of clutter returns by means of spacetime filter techniques is discussed in detail. A prerequisite for spacetime techniques is a multichannel phased array antenna.

15 Influence of the radar equation
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In this chapter we discuss issues of STAP by taking the target properties and the clutter environment into consideration.

16 Special aspects of airborne MTI radar
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In this section we discuss briefly the effect of antenna array errors on the clutter rejection performance. There are several kinds of error sources in an array antenna, such as tolerances of the sensor positions, amplification errors which result in amplitude and phase jitter as well as IQ and delay errors.

Appendix: Sonar applications
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This appendix focuses on the possibilities of spacetime processing under the boundary conditions of an acoustic waveguide.

Back Matter
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