a Matlab package for phased array beam shape inspection

52 A FIGURES TO CHAPTERS 2–7
1
2 3 4
1
2 3
u y
0
5 1 6
u y
0
4 1 5
7 8 9
6 7
−1
−1
−1 0 1
−1 0 1
u x
u x
(a) θ 1 = 4.0 ◦ , g 4 = g 9 = -23 dB
(b) θ 1 = 5.0 ◦
Grating
1
2 3 4
1
2 3
u y
0
5 1 6
u y
0
4 1 5
7 8 9
6 7
−1
−1
−1 0 1
−1 0 1
u x
u x
(c) θ = 4.0 ◦ , g 4 = g 9 = -11 dB
(d) θ 1 = 5.0 ◦
Figure 20: Explaining the directivity dips. This figure illuminates the origin of the dip
at θ ≈ −4.5 ◦ in the directivity curves of Fig. 19. In panels (a) and (b), the
array elements are vertical, in panels (c) and (d), the elements have been
tilted to φ E = 0, θ E = 40 ◦ . When the marker beam (beam 1) is phase-steered
from 4 ◦ to 5 ◦ , two grating beams move out of the circle of visibilitity. For the
tilted elements, a still significant amount of power is suddenly taken and then
re-released, for the gain of both the horizontal beams is still only about 10 dB
down from the main beams. Instead, for the vertical elements, beams 4 and
9 have so little gain that what they do near the boundarary of the visibility
circle does not matter in the power budget. The figure was produces with
planearray.