> #3 =A0I want to use NFC for remote control purposes and data acquisition.=
 =A0I intend to design an NFC reader and some different slave units. =A0I w=
ould like to be compatible with what is coming out in the smart phone area.=
 =A0I would prefer to use the simplest protocol possible. =A0Any suggestion=
s on protocol and configuration ?
>
> #4 =A0It has been suggested that I could roll my own RF circuitry. I wond=
er if it would be better to find a chip for this ( NXP maybe ? ) or roll my=
 own ?

FWIW: =A0Note that NFC is not RF, by definition.

If you want low cost and easy startup you can start by "rolling your
own with a transmitter using =A0modulated or switched sine wave of
suitable frequency, driving a resonant inductor or loop. Receiver is a
tuned circuit and a half wave diode detector. Start with two "pot
core" or U core or whatever - drive one, receive with other.

cm's of range is easy. More to much more is easy with more open tx loop top=
logy.

MIT managed 'across a room" at 60 Watts at ~- 50% efficiency afair.

IPT robotic powering people achieve kWs to 10's of kW at highish
efficiencies across cms.

I've had =A0dozens of "stations" =A0with power transfers of say 1 - 10
Watt/station and bidirectional signalling at 100's of kbps (AFAIR)
with say 10 mm clearance. TX loop was standard mains "tps" wiring (100
mm 2 wire loop) with ferrite U cores placed on or near insulated
conductors as and where required.

Resonance of tx and rx is a major "secret"

Having at least one inductor have a large spatially distributed field
is another.

FWIW, Jodrell Bank Radio telescope near field extends to beyond
atmosphere - makes RF testing difficult [tm]. May set a record for NFC
though :-).



=A0=A0 =A0 =A0 =A0 =A0 Russell McMahon

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