CMOS Design of a Chaos-Based Masking System for Biomedical Signals Applications

This work shows the development of an electrocardiogram (ECG) data masking system based on double-scroll synchronized chaotic oscillators. The contribution is devoted to the introduction of a CMOS implementation of a double-scroll chaotic oscillator, which is designed by taking advantage of the intrinsic hyperbolic tangent-type characteristic of the operational transconductance amplifier (OTA). The chaotic behavior of the CMOS oscillator is guaranteed by plotting the bifurcation diagram and evaluating the Lyapunov exponents. In this manner, a masking system based on CMOS chaotic systems is designed to protect privacy while transmitting ECG signals effectively. Basically, the chaotic time series is processed to generate pseudorandom signals in a continuous-time domain. Mathematical modeling and simulation results under a UMC 180-nm CMOS fabrication process demonstrate that the proposed masking system is well suited to provide hardware-level security in the chaotic encryption of biomedical signals.