Improvements in the Design and Performance of PWLL

摘要

The p-Wave Locked Loop provides instantaneously the p to p time interval of the applied ECG and enables us to perform heart rate variability studies on the basis of p_p variation. The first version of the PWLL started its processing action with the determination of r-wave first and waited for the user to operate manually a switch to transfer its action for detecting p-wave and then locking to its variation. In the next version of the PWLL the changeover was made in the circuit itself after a prefixed time. Nevertheless, for certain p_p variation of severe heart patients the duration might be quite a long and the prefixed delay for changeover might fail to lock. In this improved version of the PWLL, the time duration for changing over to p_p is made dependent on p_p itself. Therefore, the locking time is dynamic which depends on the nature of p_p variation of the ECG input. If unlocking happens due to erratic nature of the ECG it would again lock quickly and the relocking time is estimated based on circuit components and devices. Besides the improvement in locking features, improvements in other performance characteristics of the PWLL are proposed and analyzed. A nearly ideal PWLL is emulated and the responses of the practical PWLL and emulated PWLL are compared and analyzed as to help in reaching optimum hardware parameters. This performance improved PWLL would enable to ease further the heart rate variability studies.