Page 204 - Fundamentals of Radar Signal Processing

FIGURE 3.16 Geometry of a uniform linear array antenna.

(3.22)

The equivalent spatial frequency in cyclical units is just

(3.23)

The angle of arrival θ can vary between –90° and +90°, so the spatial frequency
bandwidth becomes

(3.24)

It follows immediately by the Nyquist criterion that the required spatial
sampling interval is

(3.25)

Thus, the elements of the array should be spaced no more than λ/2 meters apart

to avoid aliasing of spatial frequencies. 9
Many practical arrays, particularly large wideband systems, employ more
complicated architectures effectively having two spatial sampling intervals. The
complete antenna array is broken into a relatively small number of subarrays,
each of which is populated with elements obeying the Nyquist spacing of Eq.
(3.25). Since the multielement subarrays are necessarily separated by multiples