Grating lobe
= Grating lobe
A <grating lobe> is an additional principal maximum caused by spatial sampling in a <phased array>. A regularly spaced linear array steered towards $\theta_0$ also has maxima wherever $\sin\theta=\sin\theta_0+m\lambda/d$ lies in $[-1,1]$. Taking $d<\lambda/2$ excludes such maxima for all steering angles; $d=\lambda/2$ is the usual limiting choice, with an endfire degeneracy at the extreme scan directions.