Imec, Holst deliver ultra-low-power processor for medical monitoring system

Leuven, Belgium — Imec and Holst Centre have announced an analog-signal processor ASIC, or what the organizations call an ASP, that reduces the overall power consumption of an ambulatory heart activity signal monitoring system by more than five times. The device, unveiled at the International Solid State Circuit Conference, represents a major step towards autonomous wireless sensor systems that constantly monitor a patient’s health for diagnosis or chronic illness, says the companies.

“This breakthrough is a major step towards constant ambulatory monitoring of people using energy harvesting, which increases the comfort level of patients and is a cost- and time-efficient alternative for current monitoring systems,” says Bert Gyselinckx, general manager of imec at the Holst Centre, in a statement.

The ASP, developed within imec’s and Holst Centre’s HUMAN++ program, uses an adaptive sampling scheme based on activity detection. This reduces the amount of data which needs to be processed by the digital signal processor (DSP) or transmitted by the radio. Typically, in biomedical wireless sensor systems, a lot of power consumption is wasted in the DSP or radio by continuously processing biopotential signals (e.g. ECG or electrocardiogram), or transmitting raw data over the wireless link, according to the organizations.

In addition, the groups say that ambulatory biomedical sensor systems also suffer from motion artifacts, which impact the robustness of detection algorithms and demands even more processing power.

By preprocessing the signal, a simplified DSP can be used for accurate R-peak detection resulting in lower power consumption of the DSP, according to research, and motion artifacts are detected by continuously monitoring the electrode-tissue impedance. The impedance monitoring can also be used for ensuring signal integrity by continuously checking the electrode connectivity, according to the groups.

The ASP offers a record low power consumption of only 30 uW operating from 2V. It consists of an ECG readout channel, two quadrature readout channels for continuous-time monitoring of electrode-tissue impedance, and two quadrature readout channels for tracking signal fluctuations in a specific frequency band.

The device also includes an activity detector that senses the frequency content of the ECG signal and adapts the sampling rate of the integrated analog to digital converter (ADC) for the digitization of the ECG signal. The ASP stage reduces the power consumption of the DSP and wireless transmission by 11 and 6 times respectively.

This results in an overall system power dissipation of below 300 uW for the complete wireless heart activity signal monitoring system, which is more than 5 times more power efficient than its predecessors, according to the company. This power budget also includes the additional functionality of continuous-time electrode-tissue contact impedance measurement.

Industry can get access to this technology by joining the Human++ program as a research partner or through licensing agreements for further product development.

Tags: Analog-Signal Processor ASIC, Electronics Advocate, Heart Monitoring System, International Solid State Circuit Conference, Medical, Monitoring System, Signal Processor, Wireless Sensor Systems

This entry was posted on Monday, February 8th, 2010 at 4:15 pm and is filed under Breaking New Ground. You can follow any responses to this entry through the RSS 2.0 feed.