TABLE OF CONTENTS Signal reception using an array of sensor elements has long been an attractive solution to severe problems of signal detection and estimation because an array offers a means of overcoming the directivity and beamwidth limitations of a single sensor element. The advent of highly compact, inexpensive digital computers has now made it possible to exploit well-known results from statistical detection and estimation theory and from control theory to develop array systems that automatically respond to a changing signal environment. This self-adjusting or adaptive capability renders the operation of such systems more flexible and reliable and (more importantly) offers improved reception performance that would be difficult to achieve in any other way.
Conventional signal reception systems are susceptible to degradation in signal-to-noise ratio (SNR) performance because of the inevitable presence in the signal environment of undesired "noise" signals that may enter the system either by the beam pattern sidelobes or by the mainlobe. These noise signals may consist of deliberate electronic countermeasures (ECM), nonhostile RF interference (RFI), clutter scatterer returns, and natural noise sources. Such SNR degradation may be further aggravated by antenna motion, poor siting conditions, multipath ray effects, and a constantly changing interference environment. As radar and communication traffic increases, the suppression of interference becomes more important in all applications.
Adaptive arrays are currently the subject of extensive investigation as a...
