I am named as inventor in a US patent (assigned to others) about 
1988-1989 (I can dig up details) which involved substantial inductive 
power transfer to remote units AND signalling across the system using 
the power transfer media to and from multiple remote units. So, my 
previous questions were somewhat pertinent. Worked quite well. I was 
transferring several watts per unit with 10's of units.

I still have the 100m power loop running around my house :-)




        Russell


> However, that paper pointed me to a related study E. Richley and L. 
> Butcher,
> "Wireless Communications Using Near Field Coupling", U.S. Patent No.
> 5,437,057 (issued July 25, 1995).
>
> http://www.research.ibm.com/journal/sj/384/zimmerman.pdf
>
> Magnetic field. Richley has implemented a PAN for Weiser's 
> ubiquitous
> computers using magnetic fields. The quadratic attenuation of 
> magnetic field
> with distance allows the creation of picocells, 6 cubicmeters per 
> base
> station, allowing spatial allocation of bandwidth. The system uses a 
> 5 MHz
> (megahertz) carrier to achieve 240 Kbps (kilobits per second) and 
> consumes
> only 10 milliwatts power.7 Magnetic field is unimpeded by bodies, so 
> human
> shielding is not an issue.


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