IEEE Trans Biomed Circuits Syst. 2010 Jun;4(3):171-80. doi: 10.1109/TBCAS.2010.2045756.
We present the design and implementation of linear-phase delay filters for ultra-low-power signal processing in neural recording implants. We use these filters as low-distortion delay elements along with an automatic biopotential detector to perform integral waveform extraction and efficient power management. The presented delay elements are realized employing continuous-time OTA-C filters featuring 9th-order equiripple transfer functions with constant group delay. Such analog delay enables processing neural waveforms with reduced overhead compared to a digital delay since it does not requires sampling and digitization. It uses an allpass transfer function for achieving wider constant-delay bandwidth than all-pole does. Two filters realizations are compared for implementing the delay element: the Cascaded structure and the Inverse follow-the-leader feedback filter. Their respective strengths and drawbacks are assessed by modeling parasitics and non-idealities of OTAs, and by transistor-level simulations. A budget of 200 nA is used in both filters. Experimental measurements with the chosen filter topology are presented and discussed.
我们提出了用于神经记录植入物中超低功耗信号处理的线性相位延迟滤波器的设计和实现。我们将这些滤波器用作低失真延迟元件，并结合自动生物电位检测器，以执行积分波形提取和高效的功率管理。所提出的延迟元件是使用具有恒定群延迟的 9 阶等纹波传递函数的连续时间 OTA-C 滤波器实现的。与数字延迟相比，这种模拟延迟通过不进行采样和数字化，可以处理具有较低开销的神经波形。它使用全通传递函数来实现比全极点更大的恒定延迟带宽。为了实现延迟元件，比较了两种滤波器实现：级联结构和逆跟随领导者反馈滤波器。通过对 OTA 的寄生和非理想性进行建模，并通过晶体管级仿真，评估了它们各自的优缺点。两个滤波器都使用 200nA 的预算。还介绍和讨论了所选滤波器拓扑的实验测量结果。
