Level-crossing ADC modeling for wireless electrocardiogram signal acquisition system

The wireless biomedical acquisition and transmission (Wibio'ACT) is a contributive project for real-time electrocardiogram (ECG) monitoring based on a special level-crossing analog-to-digital converter (LC-ADC). The authors present, as the first step in their design flow, modeling and simulation results of the converter in the presence of noise in ECG and comparator errors. Compared to pulse code modulation (PCM) and differential pulse code modulation (DPCM), it is shown that the LC-ADC is more suitable for the digitization of the biomedical signal. Using LC-ADC allows achieving a percentage root mean square difference (PRD) less than 2 % which is the criteria for an efficient reconstructed signal quality. As far as it concerns the comparator non-idealities, a comparator delay higher than 4 ns, which is equal to 0.21 % of the LC-ADC timer clock period, may imply a PRD higher than 2 %. Besides, the comparator offset voltage impact varies with the design considerations namely the bit resolution and the timer clock period.