Thursday, September 13, 2007

Medical's wireless squeeze

You don't find many requirements tighter than these. Power consumption at 100 nanoW and duty cycles of operation just 0.01 percent of the time. That's the goal for wireless links in cardiac implants that aim to stay active 7-10 years before a surgical replacement is needed.

Thanks to Paul Stadnik, RF engineering manager at implant maker Biotronik, for passing on to me a milestone standards makers hit this summer for this technology. The TG30 group responsible for medical standards under the European Telecommunications Standards Institute ratified in July a new low power, low duty cycle protocol for the Medical Implant Communications Services band blessing this use in the 402-405 MHz MICS band.

The standard is used to let implants communicate status information typical once a day with a home monitoring system. The FCC is studying a similar standard. To date it only recognizes this use in the 401 and 406 MHz MICS sidebands, but a ruling aligning US rules with those in Europe could come any day.

Biotronik fielded some of the first implants to use MICS based on its own ASICs. But a handful of chip makers are delivering MICS chips now including AMI Semi, Texas Instruments and Zarlink.

Meanwhile TG30 has started a two-year effort to identify new spectrum needs for implants that need more than the 100 Kbits/s or so you can get with MICS and fancy modulation schemes. Brain implants that capture signals and transmit them wirelessly to controllers for artificial limbs are one of the chief applications for a broadband implant standard.

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