A High CMRR Front End Design with AC Coupling for QRS Detection

The noise coupling and artifact removal for ECG front end is proposed, Electrocardiography signals may be corrupted by various kinds of noise. Different noise sources occurring due to motion artifact, power line interference, instrumentation noise etc., is analyzed and proper approach is made. A filtering approach is done for the removal of artifact, offset noise and unwanted frequencies.The CMRR of the instrumentation amplifier is improved by AC coupling with a DC restoration loop along with the DRL circuit. A DRL (Driven Right Leg) is designed to reduce the common mode noise. The proposed model has a CMRR of 120dB.As the noise is the major phenomenon in the filter designing the filters are choose such that they have a low sensitivity. The sensitivity of some important RC-active filter realizations including Gyrator are derived and compared. According to the application of ECG monitoring, among the different configuration the low sensitivity filter is chosen w.r.t. to experimental results. Practical realization is done for low-pass, high pass and notch filter for different Q and β and the results are checked.The circuits used have zero sensitivity for resistors and capacitors.