Grating lobes

Updated October 8, 2011

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New for September 2011! A grating lobe occurs when you steer too far with a phased array and the main beam reappears on the wrong side. Elements must be spaced properly in order to avoid grating lobes. The equation for maximum spacing is a function of wavelength of operation and maximum look angle:

Thus for a 30 degree look angle, dmax is (2/3)xlambda, while for a 60 degree look angle, dmax is 0.54 lambda.

The following images were contributed by Luke (thanks!) here we have a phased array that is being scanned past its intended 45 degree range. One of these days we'll knit all the images together into a video.