Institute of Biomedical Engineering Research, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea.
Department of Biomedical Engineering, Kyungpook National University Hospital, 130 Dongdeok-ro, Jung-gu, Daegu 41944, Korea.
Sensors (Basel). 2021 Apr 16;21(8):2809. doi: 10.3390/s21082809.
In this study, we developed a new type of wireless transmission system for use in partially implantable hearing aids. This system was designed for miniaturization and low distortion, and features direct digital modulation. The sigma-delta output, which has a high SNR due to oversampling and noise shaping technology, is used as the data signal and is transmitted using a wireless transmission system to the implant unit through OOK without restoration as an audio signal, thus eliminating the need for additional circuits (i.e., LPF and a reference voltage supply circuit) and improving the ease of implantation and reliability of the circuit. We selected a carrier frequency of 27 MHz after analysis of carrier attenuation by human tissue, and designed the communication coil with reference to both the geometry and required communication distance. Circuit design and simulation for wireless transmission were performed using Multisim 13.0. The system was fabricated based on the circuit design; the size of the device board was 13 mm × 13 mm, the size of the implanted part was 9 mm × 9 mm, the diameter of the transmitting/receiving coil was 26 mm, and the thicknesses of these coils were 0.5 and 0.3 mm, respectively. The difference (error) between the detected and simulation waveforms was about 5%, and was thought to be due to the tolerances of the fabricated communication coil and elements (resistors, capacitors, etc.) used in the circuit configuration of the system. The number of windings was reduced more than 9-fold compared to the communication coil described by Taghavi et al. The measured THD was <1% in the frequency band from 100 Hz to 10 kHz, thus easily meeting the standard specification for hearing aids.
在这项研究中，我们开发了一种新型的无线传输系统，用于部分可植入助听器。该系统旨在实现小型化和低失真，并具有直接数字调制功能。由于过采样和噪声整形技术，Σ-Δ输出具有高信噪比，可用作数据信号，并通过 OOK 无线传输系统传输到植入单元作为音频信号，从而无需恢复，消除了对额外电路（即 LPF 和参考电压供应电路）的需求，并提高了电路的植入便利性和可靠性。我们在分析了人体组织对载波衰减的影响后，选择了 27 MHz 的载波频率，并参照几何形状和所需的通信距离来设计通信线圈。使用 Multisim 13.0 对无线传输的电路设计和模拟进行了设计。根据电路设计制造了系统；设备板的尺寸为 13mm×13mm，植入部分的尺寸为 9mm×9mm，发射/接收线圈的直径为 26mm，这些线圈的厚度分别为 0.5mm 和 0.3mm。检测到的和模拟的波形之间的差异（误差）约为 5%，据认为这是由于制造的通信线圈和系统电路配置中使用的元件（电阻器、电容器等）的公差造成的。与 Taghavi 等人描述的通信线圈相比，匝数减少了 9 倍以上。在 100Hz 至 10kHz 的频带内，测量的总谐波失真（THD）<1%，因此很容易满足助听器的标准规范。
