From: Eugen Leitl (eugen@leitl.org)
Date: Sun Apr 28 2002 - 03:35:01 MDT
On Sat, 27 Apr 2002, Phil Osborn wrote:
> I assumed that that problem would be fixed by now - which hasn't
> happened yet, so far as I know.
Natural technology for localizers is ultrawideband, aka digital pulse
radio. The same technology allowing you to time minor variations in pulses
also allows you to time them sufficiently accurate to achieve cm
resolution. One of the startups using UWB specifically for localization is
Aetherwire http://www.aetherwire.com/
I believe Tim May is acting as an investor in a UWB startup, so he will be
probably the right person to ask for comments.
> stealing for fencing purposes uneconomical. In the
> early '90's they were already used for that purpose by
> the British Motorcycle Association, who sold a kit to
> its members for about $50 U.S. and coordinated with
> the police who had hand-held readers tied to a
> universal database.
One of more low tech approaches is to use microdot paint.
> Failing to solve the pulse power problem, however, you
> could use either a universal broadcast power grid to
> keep a little on-board capicitor charged, or make it
> just smart enough to tune to whatever broadcast power
> was locally available - as in local FM radio stations
If the localizers are small, you've got geometry problems. The length of
the antenna has to be about lambda/4 for it to absorb sufficiently. The
exciting frequency has to be ~microwave (~cm) to absorb efficiently. While
flooding the environment with low power HF is doable technically
(especially, if you illuminate spots in the landscape from LEO and GEO
platforms), but this is bound to have impact on biology.
> - for the same purpose, using a tiny trickle of
> current to build up a charge for one or more ID
> chirps.
What's wrong with a photocell charging a capacitor?
> Instead of trying to embed the actual info to be
> displayed in the chip, then, I assumed that the chip
> would simply tell the user's wearable system where to
> look in the universal index, which would be duplicated
> on non-rewritable media and available worldwide via
> cellular, satellite or whatever.
Are we talking about localizers, or RFID tags? Are RFID tags to be
difficult to forge (tamperproof, random tag challege based crypto
protocol), or just dumb (radiate, say, a 64 bit number in clear)? In
latter case an early product is already available:
http://www.hitachi.com/products/material/rfid/
(see the presentation link for details and specs). Some other folks have
prototyped electrostatically powered tags which use carbon-ink-jet printed
antenna. No doubt, one could make a completely printable RFID tag with
polymer semiconductor inks.
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