Question

Which of the following cannot be the separation between elements in a broadside array to avoid grating lobes?

(a) 4λ/2

(b) λ/2

(c) 3λ/2

(d) 5λ/2

I have been asked this question in an online interview.

This interesting question is from Broadside Array topic in section Antenna Array of Antennas

Answer 1

The correct option is (a) 4λ/2

For explanation I would say: The spacing between elements should not equal to integral multiples of λ to avoid grating lobes. The option 4λ/2=2λ

So when d=2λ grating lobes occurs which means maxima are found at other angles also. So this is not a desired spacing.