What is the purpose of apodization in array design?

• A. To increase grating lobes.
• B. To reduce grating lobe strength by varying excitation across elements.
• C. To shorten the probe.
• D. To improve impedance matching.

Answer: (B)

Apodization shapes the array’s aperture by applying a gradual, nonuniform excitation across its elements. By weighting the elements—usually lowering the outer elements’ amplitudes—you taper the aperture’s edges. This reduces energy sent into directions away from the main beam, which lowers grating lobes and other sidelobes that can create artifacts and degrade image quality. The trade-off is a slight broadening of the main lobe and a reduction in peak intensity, but it doesn’t physically shorten the probe or change impedance matching. So the best description is that apodization reduces grating lobe strength by varying excitation across elements.