A generic ASIC and DSP based ambulatory electrophysiological recorder

Describes the development of an ambulatory recorder that is capable of storing a range of electrophysiological signals emanating from the human body. The motivation for this work was primarily the ambulatory monitoring of fetal heart rate (FHR) using cutaneous electrodes on the mother´s abdomen. Such a system requires an analogue front end that contains amplification and filtering to remove base line drift, an analogue to digital converter (ADC) to digitise the raw FECG and solid state storage capability. Since the data required is the FHR it is then necessary to extract the FECG from the maternal ECG and noise signals and calculate the time between the FECG beats. Hence on board processing is also required and for this reason a digital signal processor chip (DSP) is included in the system. Since the instrument needs to be portable it is important for the unit to be lightweight and small, consequently a custom integrated circuit has been used to replace the analogue front end, ADC and DSP interface circuitry, By making the gain, bandwidth, sampling frequency and resolution programmable and modifying the DSP algorithm the authors have the basis for a general electrophysiological recorder capable of recording other signals such as the Electrogastrogram (EGG), Electrohystogram (EHG) and Electromyogram (EMG) to name but a few