Re: RFID chip has battary in it or not
- From: "JJ" <johnjakson@xxxxxxxxx>
- Date: 6 May 2006 23:17:16 -0700
Weng Tianxiang wrote:
Hi,
Recently I received a RFID chip to open company's door when entering
office building.
It is very easy to carry and use like a key.
I would like to know whether it contains a battary or not.
If there is no battary in it, how can a circuit work running with Radio
Frequency?
Weng
Know how an AC power transformer works ?
The power going in doesn't have to be a fixed frequency, it can be
modulated a little. The secondary coil may have a switchable shunt
across it. Combine them into a communications system.
Increase the distance till they are quite separate and the secondary
coil can be quite small and embedded on a Si chip as coils surrounding
the chip or on a carrier pcb. Still power transmitted in the primary
can reach to some degree the secondary and be rectified, stored and the
local logic can both detect variations in the received power frequency
(data input) and shunt the secondary coil (data output) and that can be
detected by the power transmitter as changes in the impedance of the
primary coil. Datarates of 1MBps or so even 20 years ago in close
proximity.
Well thats as I understood it 15yrs ago, I guess it finally cought on.
I once developed the smart idea of storing music albums on a compressed
ROM chip and using RF as the means to both power and read/play the
music out. At the time the Rom would have only been 64MBits, 1GByte
Flash & MP3 was more than a decade later.. This would have made the
device contactless and fully protected from scratching etc unlike the
CDs we still have today.
John Jakson
transputer guy
.
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- From: Weng Tianxiang
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