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It's not an appropriate (element) space

By: Vineet Kochhar

Ideally, the spacing (Δx) between radiating elements in a phased array should be as follows:

Δx < λ/(1+sinθs )

Where θs is maximum scan/look angle. For example, θs = 90 degrees, Δx < λ/2

Scanning above this angle will cause grating lobes which is an artifact where strong radiation occurs in an unintended direction.

With λ/2 spacing between radiating elements, we have the following when scanned to 50 degrees:

Full Field of View (θs = 90 degrees)
Main Lobe at 50 degrees
2D Antenna Gain Contours shown
3D Beam Pattern shown

With 0.7λ spacing between radiating elements, we have the following when scanned to 50 degrees:

Limited Field of View (θs = 25.3769 degrees in elevation angle)
Main Lobe at 50 degrees with grating lobe
2D Antenna Gain Contours shown
3D Beam Pattern shown with grating lobe
Posted: 10/15/2018 7:00:00 AM


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