imec Develops 400 MHz Wireless Transceiver for Smart Ingestible & Implantable Pills

imec, a leading research and innovation hub in nanoelectronics and digital technologies has presented the first mm-scale wireless transceiver for smart insertable pills at ISSCC 2020. It is the first breakthrough in imec’s aspiration to realize autonomous ingestible sensors that can measure health parameters such as gut health and transmit the data outside the body in real-time.

Digestive processes and gastrointestinal diseases are hard to diagnose. Current procedures like endoscopic inspection and stool sample analysis are uncomfortable and only provide one-time observations. Ingestible health trackers, small enough to be swallowed, could collect information over a longer period of time and transmit the data outside the body. Moreover, fixating the ingestible sensors along the gastrointestinal tract, enables longer recordings in specific places of interest. Also, this would increase the comfort of the patient, as he or she could stay out of the hospital while data are collected and sent in real-time to the doctor.

Up to 30 Times Smaller Volume than the State-of-the-Art

One of the challenges in realizing electronic pills is developing a wireless link that meets the volume, power and performance constraints for reliable data transmission during the period of time that the sensor is collecting data inside the body. Imec’s new wireless transceiver supports the medical 400 MHz frequency bands such as MICS (Medical Implant Communication Service), MEDS (Medical Data Service) or MedRadio (Medical Device Radiocommunications Service). The wireless transceiver is implemented in 40 nm CMOS and includes an on-chip tunable matching network (TMN) that enables a miniature 400 MHz antenna, and as such avoids external and bulky matching components. The whole transceiver module including antenna occupies a volume of <55 mm3 which is up to 30 times smaller than state-of-the-art devices. The whole wireless module occupies an area of 3.5 by 15 mm2, including a 3.5 by 3.8 mm2 PCB and a miniature 400 MHz antenna. The small form factor is realized thanks to a new crystal-free transceiver architecture, alleviating the need for an off-chip crystal device, and a 2 mm2 transceiver IC with the on-chip TMN. A small area is further achieved by a TX/RX shared matching network with only one on-chip inductor and a single-branch phase tracking RX.

Reliable Data Transmission Outside the Body

While inside the body, the pills are covered by multiple layers of tissue. Therefore, a wireless system operating in the 400 MHz medical band is preferable because of lower tissue attenuation compared to higher-frequency bands and ensures a reliable and interference-free channel for the implants. Furthermore, the on-chip tunable matching network using self-calibration expands impedance matching up to a VSWR (voltage standing wave ratio) of 4.8, covering a wide range of impedance variation in the body, equivalent to a filled and empty stomach. To realize crystal-free operation, imec implemented an over-the-air network-assisted carrier recovery for large frequency offsets of up to 320 ppm.

Chris Van Hoof, vice president connected health at imec and general manager of OnePlanet research center commented that smart ingestible pills and smart implants offer endless possibilities in what can be measured and treated in the body. This trend leverages on the miniaturization revolution in nanoelectronics, that enables smart, small and lightweight devices with minimal power consumption and maximal patient comfort. However, the development of such devices brings along a specific set of challenges.

Click here to read the article "Ingestibles: from medical research tool to smart-health application".

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