# how to understand grating lobe problem in broadside array

#### yef smith

Joined Aug 2, 2020
185
Hello,In a broad side array we have a radiation pattern which Array factor development shown bellow.
I can understand what is the problem that is called "grating lobe"
We bellow have th Array paatern expression howcan i see the grating lobe problem from it?
In the last photo we have an expression but i cant see the intuition of how to get it?
Thanks.

#### Delta prime

Joined Nov 15, 2019
809
Hello there This looks like homework and I really like it here I can't give you the answer but can you give me your best attempt at solving it?
I'll give you a hint it's the process when used with the calculator chug and plug.

#### yef smith

Joined Aug 2, 2020
185
i read its because of wrapping every 2pi ,but i could not imagine how large "d" makes this wrapping.
Is there some intuition you can help me with?
Thanks.

#### yef smith

Joined Aug 2, 2020
185
Hello ,I have tried to implement the grating lobes into full mathematical example as shown in the photo bellow.

i understand that grating lobe happen when two elements get the same phase for example 10 and 10+360=370
could you please guide me ragarding how to update my example so i will see grating lobe with the main lobe?
Thanks.

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