Tiny Radio Broadcasts from Your Insides

Medical implants (and ingestibles) have escaped the Star Trek TNG set and entered the real world to the tune of a projected annual increase of nearly 11% in the U.S. A 2003 report from the Freedonia Group (www.freedoniagroup.com) puts the 2007 total at $24.4 billion. These devices range from the familiar pacemaker to little cameras that, when swallowed, send back a video report on conditions in the lower digestive track (see Sensors, September 2000, Research & Developments, "Camera-in-a-Capsule: An Easy Pill to Swallow"). Each requires a particular mix of control, monitoring, and communications capabilities, and Cambridge Consultants (CC) is working to fine-tune the IC core for individual applications.

 A new low-IF radio transceiver can report on implanted and ingested medical devices such as pacemakers and pumps.
A new low-IF radio transceiver can report on implanted and ingested medical devices such as pacemakers and pumps.

SubQore, CC's intelligent low-IF (intermittent frequency) radio transceiver architecture, was adapted from high-efficiency pager technology. Designed for in-body medical diagnostic and therapeutic use, it is intended for implementation on system-on-chip (SoC) units (subcutaneous radios can be the size of a button). It will operate in the 402–405 MHz Medical Implant Communications Service frequency band, endorsed by the FCC and ETSI and emerging as a global standard. Because the only other user of this band is meteorological equipment, the potential for interference is minimized and economy of scale is enhanced through standardization.

SubQore's energy requirements are negligible—an average current draw of <1 µA and <1.7 mA peak for a 0.05% duty cycle, 400 Kbps bidirectional communications application. This translates into a life span greater than 10 years for a lithium cell in a standard pacemaker, for example. However, flexibility built into the radio design also allows the chip to be used for other systems with short-term high-data-rate communications requirements such as that tiny camera.

The widest block in this chip-scale magnetometer is a sealed, transparent cell containing a vapor of rubidium atoms.
The widest block in this chip-scale magnetometer is a sealed, transparent cell containing a vapor of rubidium atoms.

In its basic form, SubQore's radio uses digital phase-shift keying data modulation, but the hardware that controls modulation has been designed to provide a degree of DSP flexibility that will support higher-efficiency schemes for more demanding applications such as video transfer. The lean RISC microcontroller core, XAP, provides similar flexibility and can be equipped with a range of digital and analog I/O and memory sizes to suit the application.

Short Takes
Short Takes

Among SubQore's likely applications are implantable pacemakers, defibrillators, remote telemonitors, orthopedic devices, pump controllers, nerve stimulators, and ingestible imaging and diagnostic systems.

Contact Andrew Diston, Cambridge Consultants Inc., Boston MA; 617-532-4700, [email protected], sultants.com, www.cambridgeconsultants.com.