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

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.

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.