| Title |
Effective Ultrasound Focusing Techniques Using Nonlinear Frequency Modulation |
| Authors |
장승완(Seungwan Jang) ; 윤희철(Heechul Yoon) |
| DOI |
https://doi.org/10.5370/KIEE.2025.74.3.484 |
| Keywords |
Therapeutic ultrasound; Frequency modulation; Grating lobe; Acoustic beam field |
| Abstract |
Ultrasound stimulation for the treatment of osteoarthritis has proven to alleviate patient pain and has shown the potential for cartilage cell regeneration. To improve the treatment efficacy and ultrasound focusing, the use of larger aperture and higher frequency signals is desired, but it could result in grating lobe artifacts. To resolve this challenge, this study proposes a new ultrasound stimulation technique that modulates the frequency during transmission to dynamically shift the temporal and spatial position of the grating lobes. The proposed method disperses the angle of the grating lobes over time by continuously modulating the frequency within a specific frequency range, including both linear and nonlinear modulations. To validate our approach, we produced 3-D acoustic beam fields under beam steering conditions. A transmit pulse with a single frequency at 2 MHz was compared to linear and nonlinear frequency-modulated pulses with a frequency ranging from 1-to-3 MHz. Additionally, we modeled a 64-channel 8x8 2-D array with a center frequency of 2 MHz and a 60% fractional bandwidth using MATLAB and Field II programs. For quantitative evaluation, we estimated the beam width at 3 dB and the intensity variation between the main and ? grating lobes, and the peak intensity at the focus. Overall, we found that the grating lobe decreased by up to 9.83 dB in our ? configurations and demonstrated that frequency modulation-based ultrasound stimulation shows the potential for reducing grating lobe, which is expected to be applicable to improve the safety and performance of osteoarthritis treatment. |