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Re: About wireless energy transfer
Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
At 07:58 PM 2/11/2007, Tesla list wrote:
Original poster: Ed Phillips <evp@xxxxxxxxxxx>
Original poster: Jim Lux <mailto:jimlux@xxxxxxxxxxxxx><jimlux@xxxxxxxxxxxxx>
At 07:49
Mutual coupling is always a problem in designing arrays but the
unfortunately the designer has to live with it. In designing
microwave antennas one common practice is to build a small array of
elements and to measure the coupling of elements near the center in
order to determine the required impedance matching. In general
that impedance matching can't work over all possible angles so
there is some power lost due to it. Sounds as if you may be
working with some interesting array concepts - can you share any of them?
My (funded) research was for arrays that look quite conventional
(patch radiators roughly 1/2 wavelength apart, so they have
significant mutual coupling), but where the physical positions and
orientations might vary (because, for instance, they are on a
flexible substrate) or where the electronics connected to them varies
over time (temperature variations changing phase shift through
amplifiers or input and output Z of the LNA or PA.. that kind of
thing). The idea was to distribute electronics and computational
capability throughout the array (i.e. a CPU at every element) that
could measure the couplings and "back it out" for each element to
make a self calibrating array. If you take an array with, say,
10,000 elements, you could have 100 of them out of service (i.e.
calibrating) at a given time without greatly affecting the array
performance. Over 100 pulse times, you'd get to all the elements,
which is less time than the time scale of the variations you're
calibrating out.
http://www.luxfamily.com/jimlux/rtd.htm
has links to poster and annual report for the funded work. The
technique can work, but it appears that there's not a huge demand
(within NASA) for large space borne radar antennas of this type. All
the identified requirements can be met with fairly conventional
phased array techniques, so the added risk of a new and novel
technique to get better performance isn't worth it.
Subsequently, I've been doing something similar on my own time for a
portable HF array for ham radio applications. The "use case" is:
Everything fits in the trunk of my car... Pull to a stop, deploy the
antennas, run the cal routine, and be on the air in <20
minutes. Here you need to calibrate out the effects of the antenna
siting and local soil properties.
Jim