Which term describes additional weak beams emitted from a multielement transducer that propagate in directions different from the primary beam?

Which term describes additional weak beams emitted from a multielement transducer that propagate in directions different from the primary beam?

• A. Grating lobes
• B. Side lobes
• C. Near zone
• D. Doppler shifts

Answer: (A)

Spurious energy that travels in directions away from the main beam comes from the array itself. When the transducer elements are spaced more than about half a wavelength apart, their combined emission creates extra maxima at angles off the steering direction. These are grating lobes. They are different from side lobes, which are weaker beams that lie near the main beam due to the finite aperture but don’t extend as far away in angle. The near zone is the region in front of the transducer where the beam is still forming, and Doppler shifts refer to changes in frequency from motion, not additional beams. So the term describing those additional weak beams in directions different from the primary beam is grating lobes.

Spurious energy that travels in directions away from the main beam comes from the array itself. When the transducer elements are spaced more than about half a wavelength apart, their combined emission creates extra maxima at angles off the steering direction. These are grating lobes. They are different from side lobes, which are weaker beams that lie near the main beam due to the finite aperture but don’t extend as far away in angle. The near zone is the region in front of the transducer where the beam is still forming, and Doppler shifts refer to changes in frequency from motion, not additional beams. So the term describing those additional weak beams in directions different from the primary beam is grating lobes.