D. G. Tucker 4] 
RANGE 
—+6° 
oO 
= 
0g 
Ww 
[-2) 
=u 
0 YARDS 
30YARDS ie 20! (b) 
(d) 
(e) (fF) 
Fig, 2.11. Comparison of multiplicative and additive scanning sonars using same array (eight channels 
from array). (Courtesy, British Institution of Radio Engineers.) (a,b) Single 18-in.-diameter sphere at 
30 yd: (a) additive system (b) multiplicative system. (c,d) Same as (a,b), but with receiver gain greatly 
increased to show effect of side lobes: (c) additive system (d) multiplicative system. (e,f) Two 18-in,- 
diameter spheres at same range of 30 yd: (e) additive system (f) multiplicative system. 
for the case where the frequencies transmitted consist of the center frequency 
@, and the two odd-harmonic difference pairs, w) +@,; and wo +3w;, where w; Kp. 
The output of one of the receiving transducers is translated in frequency to o,, 
@, +@;, and, +3, by means of a frequency changer fed with a frequency-swept 
local oscillation; thus w, is being swept through a range of frequency during 
every interval of time equal to the durationof the transmitted pulse. The narrow 
group of frequencies o,, o, +@;, andw,+3w, isthus swept up and down the delay — 
frequency characteristic (Fig. 2.13) of the "quadratic phase network" and re- 
ceives a different delay at different instants inthe sweep. The sonar information, 
being carried by the envelope amplitude of the complex signal, is then recovered 
by normal detection before being multiplied by the signal from the other trans - 
