A High-Pass Pole Shifting Technique for Bidirectional Electrophysiological Interfaces Using a Novel Tunable Analog Filter Block

This article details the design of a high-pass pole shifting technique, which can achieve a rapid recovery of the analog front-end (AFE) electronics from strong stimulation pulses and electrochemical dc offsets in bidirectional electrophysiological interfaces. The technique is implemented by making use of a novel continuous-time analog filter block that offers tunability in the applied cutoff frequency, scalability, real time, and low-noise recording capabilities, along with the capability of interfacing with various types of sensors. The measurement results of this work prove that the proposed technique can offer low integrated noise values ( $\lt 2~\mu $ Vrms from 0.5 Hz up to 4 kHz) and immediate recording of the biosignal of interest after the stimulation pulse when implemented with the specific tunable filter. The recorded biosignals are free from undesired ringing oscillations or phase shifts. All those merits render this technique as a versatile and reliable solution to be used in a wide range of applications and environments.