A linear array with element spacing of 0.6 λ is likely to exhibit which artifact, and how can you mitigate it?

• A. Side lobes; mitigate by reducing apodization
• B. Noise artifacts; mitigate by increasing bandwidth
• C. Grating lobes; mitigate by reducing spacing to ≤ 0.5 λ or applying apodization
• D. Phase jitter; mitigate by lowering PRF

Answer: (C)

Grating lobes show up when the spacing between array elements is larger than half a wavelength, creating extra peaks in the radiated field that can appear as ghost images in the image. With 0.6 λ spacing, the array falls into the regime where these grating lobes form, especially when the beam is steered away from broadside. To mitigate, reduce the element spacing to 0.5 λ or less, which eliminates grating lobes in a uniform linear array, or keep the spacing larger but apply apodization to taper the aperture and suppress the grating lobes’ amplitude (at the cost of a wider main lobe and potentially lower SNR). The other options don’t fit this spacing scenario as well: side lobes are more about windowing, while phase jitter and PRF changes target different issues rather than grating lobes.