Phased Arrays - MATLAB Simulations for Radar Systems Design - page 370

θφ ,

Figure 8.49c. 3-D plot ( space) corresponding to Eq. (8.84).

The program Ðarray.mÑ also plots the arrayÓs element spacing pattern. Figs.
8.50a and 8.50b show two examples. The ÐxÓsÑ indicate the location of actual
active array elements, while the ÐoÓsÑ indicate the location of dummy or virtual
elements created merely for computational purposes. More precisely, Fig.
8.50a shows a rectangular grid with circular boundary as defined in Eqs. (8.67)
and (8.68) with d x == a d y 0.5λ and = 0.35λ . Fig. 8.50b shows a similar

configuration except that an element spacing d x = 1.5λ and d y = 0.5λ .

8.6. Array Scan Loss

Phased arrays experience gain loss when the beam is steered away from the
array boresight, or zenith (normal to the face of the array). This loss is due to
the fact that the array effective aperture becomes smaller and consequently the
array beamwidth is broadened, as illustrated in Fig. 8.51 . This loss in antenna
gain is called scan loss,

L scan , where

 2

A
A θ

 2

G
G θ

-----  ----- 

L scan = =

(8.85)

A θ is effective aperture area at scan angle θ , and G θ is effective array gain at

the same angle.