Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx> At 07:49 PM 2/9/2007, Tesla list wrote:
Original poster: Ed Phillips <evp@xxxxxxxxxxx>I'm not disputing the case for low efficiency, for a single device, but what if there were, say, 20 or 30 of those devices within the field?"If there were the transfer to each one would have an efficiency determined by its unique coupling to the "transmitter". If they were separated from each other by enough that there was no mutual coupling between them [the receivers] then the total power would be the sum of the individual powers.
Having spent the better part of the last 5 years working on research into novel ways to do non-microwave phased arrays, the statement: "separated by enough so there's no mutual coupling" says it all...
That's the rub. At distances <1 wavelength there will always be mutual coupling to deal with..except for some "special cases" like two coils that are orthogonal.
Yes, one can come up with schemes to adjust everything to compensate for the mutual coupling, but that requires knowing what the couplings are (non trivial), a way to do the adjusting (non-trivial), and a way to do the calculations (non-trivial). All of these also require some non-zero amount of power to do.