IEEE Trans Biomed Circuits Syst. 2009 Dec;3(6):444-55. doi: 10.1109/TBCAS.2009.2027127.
We present a mixed-signal very-large-scale-integrated chip that emulates nonlinear active cochlear signal processing. Modeling the cochlea's micromechanics, including outer hair cell (OHC) electromotility, this silicon (Si) cochlea features active coupling between neighboring basilar membrane (BM) segments-a first. Neighboring BM segments, each implemented as a class AB log-domain second-order section, exchange currents representing OHC forces. This novel active-coupling architecture overcomes the major shortcomings of existing cascade and parallel filter-bank architectures, while achieving the highest number of digital outputs in an Si cochlea to date. An active-coupling architecture Si cochlea with 360 frequency channels and 2160 pulse-stream outputs occupies 10.9 mm(2) in a five-metal 1-poly 0.25-mum CMOS process. The chip's responses resemble that of a living cochlea's: Frequency responses become larger and more sharply tuned when active coupling is turned on. For instance, gain increases by 18 dB and Q 10 increases from 0.45 to 1.14. This enhancement decreases with increasing input intensity, realizing frequency-selective automatic gain control. Further work is required to improve performance by reducing large variations from tap to tap.
我们提出了一种混合信号的超大规模集成电路，可模拟非线性主动耳蜗信号处理。该硅耳蜗模拟了耳蜗的微力学，包括外毛细胞（OHC）的电动力，这是首次在相邻基底膜（BM）段之间实现了主动耦合。每个邻接的 BM 段都实现为 AB 类对数域二阶部分，代表 OHC 力的电流进行交换。这种新颖的主动耦合架构克服了现有级联和并行滤波器组架构的主要缺点，同时实现了迄今为止在 Si 耳蜗中最多的数字输出。一个具有 360 个频率通道和 2160 个脉冲流输出的主动耦合架构 Si 耳蜗，占用了一个 5 金属 1 多晶硅 0.25 微米 CMOS 工艺的 10.9 平方毫米。该芯片的响应类似于活体耳蜗的响应：当启用主动耦合时，频率响应变得更大且调谐更尖锐。例如，增益增加了 18dB，Q10 从 0.45 增加到 1.14。这种增强随着输入强度的增加而减小，实现了频率选择自动增益控制。需要进一步的工作来通过减少从抽头到抽头的大变化来提高性能。
