Evaluation of the radiation pattern of a split aperture linear phased array for high frequency imaging

Area of Science:

• Medical Imaging
• Acoustic Engineering
• Materials Science

Background:

• Developing high-frequency transducer arrays for medical imaging is challenging due to the small element size and spacing required.
• Conventional fabrication methods struggle to achieve the necessary precision for elements spaced at approximately 15 micrometers for 50 MHz arrays.
• Small element spacing is critical to prevent grating lobes in the array's radiation pattern.

Purpose of the Study:

• To introduce and evaluate a split aperture design for linear phased arrays.
• To demonstrate how this design allows for significantly larger element spacing while suppressing grating lobes.
• To theoretically assess the performance of a 50 MHz split aperture array.

Main Methods:

• Theoretical evaluation of the 3-D radiation pattern for a 50 MHz split aperture linear phased array.
• Simulation of an array with 33 transmit and 33 receive elements, measuring 1.9x1.4 mm.
• Analysis of azimuthal and elevation beam widths, grating lobe suppression, and depth of field.

Main Results:

• The split aperture design allows for 3 to 4 times larger element spacing compared to conventional arrays.
• Azimuthal beam width was measured at 90 micrometers at a 4.0 mm distance.
• Grating lobes were suppressed by at least 60 dB beyond 4.0 mm, with an elevation beam width of 220 micrometers at 4.0 mm.

Conclusions:

• The split aperture design is a viable solution for fabricating high-frequency transducer arrays.
• This approach simplifies manufacturing by allowing larger element spacing.
• The evaluated array demonstrated effective beamforming and a useful depth of field for medical imaging applications.