RE: LED Lighting?

[Brian Reynolds <Brian@xxxxxxxxxxxxxxxxxxx>]

http://www.insidetech.com/news/articles/3266-researchers-want-led-hot-spots=
-to-replace-wi-fi
=20

Or according to Harvard Uni somewhere in the USA=85=85
=20
A unique RFI-fre electromagnetic field sensing technique using an LED as
an=
RF detector is described. A double heterojunction (AlGaAs/GaAs) LED is use=
d as an RF rectifier coupled to an EM probe; it delivers proportional
light=
output with significant efficiency even at low (rectified) drive currents.=
It is shown that dc biasing of the LED to the threshold of conduction can =
be achieved by an optically powered photodiode pair. Use of fiber-optic
lin=
ks from the detector to the receiver and in the optically powered bias
arra=
ngement eliminates the possibilities of RFI. Presented here are the
sensiti=
vity and frequency response of a test probe measured over 3-30 MHz under
ne=
ar-field conditions.
=20

To: ukha_d@xxxxxxx
From: tracey.gardner@xxxxxxx
Date: Sun, 8 Mar 2009 22:22:04 +0000
Subject: [ukha_d] LED Lighting?






A remark on LED lighting was made on another list that I am a member of.

The remark was as follows,

"One thinks of LEDs as being innocent DC devices fed via a resistor.
But=20
modern designs often turn them on and off at frequencies in the kHz range,=
=20
generating harmonics going into the lower radio bands"

I also imagined that LED lighting was purely DC driven and I'd be
intereste=
d=20
to know if this statement is correct?
If it is correct does anybody have any idea of the frequencies invloved?

Thanks

Tracey









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