LECTURE 2 
SONAR ARRAYS, SYSTEMS, AND DISPLAYS 
D.G. Tucker 
Department of Electrical Engineering 
University of Birmingham 
Birmingham, England 
2.1. INTRODUCTION 
The echo-location group of the University of Birmingham has been concerned 
primarily with active sonar systems. Apart from general considerations of long 
ranges and oceanic propagation (with which we are not able to deal) it has seemed 
to us that the main directions in which sonar research must progress are: 
1. The gathering of more information about what lies within the area of 
search, and 
2. The processing and presentation of this information sothat classification 
of targets is quick and reliable. 
The more progress that is made with 1, the more difficult quick classification 
becomes, since with a human operator the sorting out of the increased informa - 
tion becomes too large a task for immediate visual decision. Yet without the 
increased information, the process could not possibly become more reliable. 
It is not possible to separate completely these two lines of work, 1 and 2, and 
a coordinated approach to them is the one which is most likely to succeed. 
To gather more information about what lies within the area of search, it is 
necessary to achieve one or more of the following: (a) higher directionality and 
(b) higher range resolution to give geometrical information—shape and size of 
targets; (c) knowledge of frequency response of targets; and (d) more rapid 
scanning. 
The direct approach to (a) is to use larger transducer arrays, but, like many 
other people, we have been looking closely into the possibilities of obtaining 
higher directionality from a given size of array by such methods as superdirec- 
tivity, multiplicative processing, multifrequency operation, and double-FM oper- 
ation. The last two methods, together with (b) and (c) above, demand the use of 
wider frequency bands in the water, andso we have had to think about both trans - 
ducers and arrays suitable for operation over a wide frequency band. The need 
for more rapid scanning is not only obvious in itself, but follows more emphati- 
cally from (a); and we have therefore done a great deal of work on the develop- 
ment of within-pulse electronic scanning systems. 
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