Which of the following minimizes the degree to which beam width varies with depth?

• A. Dynamic aperture
• B. Apodization
• C. Coprocessing
• D. Frame averaging

Answer: (A)

Dynamic aperture keeps the beam narrow across depth by adapting the active aperture as depth increases. By using more elements or adjusting focusing at greater depths, the system maintains a tighter main lobe, so the beam width varies less with depth and lateral resolution stays more consistent throughout the image.

Apodization shapes the element weights to suppress sidelobes and improve contrast, but it doesn’t fundamentally compensate for the way beam width changes with diffraction as depth grows. Coprocessing and frame averaging are processing techniques that operate on the data after it’s acquired and don’t alter the physical beam formation, so they don’t minimize depth-related changes in beam width.