Preface
Array
processing has played an important role in many diverse application
areas. Most modern radar and sonar systems rely on antenna arrays or
hydrophone arrays as an essential component of the system. Many commu-
nication systems utilize phased arrays or multiple beam antennas to achieve
their performance objectives. Seismic
arrays
are widely used for oil explo-
ration and detection of underground nuclear tests. Various medical diagnosis
and treatment techniques exploit arrays. Radio astronomy utilizes very large
antenna arrays to achieve resolution goals.
It
appears that the third genera-
tion of wireless systems will utilize adaptive array processing to achieve the
desired system capacity. We discuss various applications in Chapter 1.
My interest in optimum array processing started in 1963 when I was
an Assistant Professor at
M.I.T.
and consulting with Arthur D. Little on
a sonar project for the U.S. Navy. I derived the optimum processor for
detecting Gaussian plane-wave signals in Gaussian noise [VT66a], [VT66b].
It turned out that Bryn [Bry62] had published this result previously (see also
Vanderkulk [Van63]). My work in array processing decreased as I spent more
time in the general
area
of detection, estimation, and modulation theory.
In 1968, Part I of Detection, Estimation, and Modulation Theory [VT681
was published. It turned out to be a reasonably successful book that has been
widely used by several generations of engineers. Parts II and III ([VT7la],
[VT7lb]) were published in 1971 and focused on specific application areas
such as analog modulation, Gaussian signals and noise, and the radar-sonar
problem. Part II had a short life span due to the shift from analog modu-
lation
to digital modulation. Part III is still widely used as a reference and
as a supplementary text. In a moment of youthful optimism, I indicated in
the Preface to Part III and in Chapter III-14 that a short monograph on
optimum array processing would be published in 1971. The bibliography
lists it as a reference, (Optimum Array Processing, Wiley, 1971), which has
been subsequently cited by several authors. Unpublished class notes [VT691
contained much of the planned material. In a very loose sense, this text is
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