Case Studies - Digital Signal Processing: A Practitioner's Approach - page 124

2

A distinct minimum

0

−2

− 4

−6

− 8

−10

0 50 100 150 200 250 300

Figure 6.2 Minima in the direction of the emitter J ð k Þ¼ log ð e k Þ

This is plotted and shown in Figure 6.2, which has a distinct minimum
representing the direction of the radiating source. Numerically locating this
minimum gives the direction of the emitter.

6.3 Electronic Rotating Elements
In the previous section we saw that the phase delay between two elements can be

modulated by rotating one element around the other. The rotation need not be done
mechanically. To see how the rotating measuring system works, consider 12
elements positioned around a centre element (Figure 6.3). The delay at the ith
element is

'

2 D

2 cos

' i ¼ d i cos ð t Þ where d i ¼ ð i Þ; ð 6 : 1 Þ

Figure 6.3 Finding direction with rotating elements