Accurate Level-crossing ADC Design for Biomedical Acquisition Board

The aim of this paper is to present a wireless biomedical system for the acquisition and transmission (Wibio’ACT) of biomedical signals. This work is a part of the Wibio’ACT project which main purpose is to ensure the minimum power consumption while diagnose patients continuously and in real time. For the Wibio’ACT system, the bottleneck is the analog-to-digital conversion (ADC) since it controls the power consumption of the digital signal processing step as well as the amount of the transmitted data. In fact, in this work case, the ADC continuously measures the electrical activity of the heart to deliver the electrocardiogram (ECG) signal. Hence, among conventional ADCs, level-crossing analog-to-digital converters (LC-ADCs) have been investigated for ECG signals processing. Authors propose some design consideration of the LC-ADC. This reduces the LC-ADC output samples by 13 % to help to save the power consumption of the wireless data transmitter. The samples with a small variation are reduced by at least 44%. The performance of the proposed design is measured in terms of percentage root mean square difference (PRD) applied to the reconstructed signal quality. A PRD of 1% is verified using behavioral simulations on ECG records extracted from different databases. A timer period TC of 0.14 ms ensures an effective number of bits of 10 bits and a signal to noise ratio of 62 dB.