Design of widely tunable Mexican hat wavelet filter for cardiac signal analysis

This paper presents a widely tunable analog Mexican hat wavelet filter for ECG signal analysis. The Mexican hat function is implemented as a difference of two Gaussian low-pass filters each of which is implemented as a cascade of switched capacitor low-pass filters. The Mexican hat scale can easily be tuned across a wide range, from frequency bandwidths of a couple of Hz to few KHz, by changing the clock frequency of the switched capacitor circuits. The proposed circuit is implemented using TSMC 0.18μm CMOS process. Compared to the ideal Mexican hat impulse response the proposed implementation shows a mean square error (MSE) of 0.26-2% only over the entire tuning range.