[LINK] RFID Passport Replies
gramadan at umd.com.au
Wed Dec 1 15:29:19 EST 2004
Geoff Ramadan wrote:
>> Carl Makin wrote:
>>> Hi Geoff,
>>> Geoff Ramadan wrote:
>>>> 13.56MHz technology use inductive Coupling (not propogation
>>>> technology like 915MHz ... where you can read at several meters).
>>>> Inductive coupling is whats used by tranformers. In effect you have
>>>> two "coils" the RFID tag and the reader. They inductivley couple
>>>> between them. The best you will ever do out of such a system is 1M
>>>> with a very large antenna and a well designed system (like in the
>>>> security panels used in retail stores).
>>>> Most proximity systems only have a read range of 10cm.
>>> Is that the range required to trigger the tag into sending the data
>>> or the range required to receive the resulting signal? What is the
>>> average output power of the tag?
>>> Admittedly a 13.56Mhz directional gain antenna would be *very* large
>>> (somewhere between 2m and 10m wide and at least 2m long) so
>>> "sniffing" the tag could be a little obvious. <grin>
>> The power output is limited by the ACA to 1W EIRP
>> This will limit the design and choice of antenna.
>> The signal is the same. The magnetic field is common to the tag and
>> reader. While the field is coupled, the tag modulates this field
>> which is picked up by the reader. i.e. change is one (or either) is
>> reflected in the other.
> Now there's a detail I hadn't noticed from the industry white papers.
> Can I clarify?
> What you're saying, Geoff, is that in the lowest-power passive tags,
> communication relies not on a "point to point" radio transmission, but
> a transformer-style coupling of magnetic fields?
Yes you are correct.
RFID tags use two forms of communication:
1) Near Field - inductively coupled as mentioned above. All 13.56MHz
tags use Near Field communications techniques.
2) Far Field (or propagation) as used in UHF 915MHz - is similar to
RADAR (backscatter reflection) and uses the electric field for coupling.
One of the best introductory "white papers" on RFID, covering
technology, tags and applications can be found at:
> The reason I ask is this: you have contradicted (probably correctly!)
> nearly everything the industry likes to put in its "RFID for dummies"
> stuff that goes to the media. And what we have is a widespread
> (ubiquitous?) misunderstanding of how RFID works.
> It would be nice to correct this...
Funny that you should mention "RFID for dummies" ... this is infact what
our industry association (Automatic Data Capture Australia)
www.adca.com.au is putting together. It will be actually titled '"Data
Capture and RFID for Dummies" and will be published under the "for
Dummies" Franchise. This will come out in Q1 of next year.
As this will be supplied for free... I am happy to reserve any copies
for LINK members... please send me a separate email to
gramadan at umd.com.au and contact details.
> Message: 6
> Date: Wed, 01 Dec 2004 11:08:06 +1100
> From: Jan Whitaker <jwhit at melbpc.org.au>
> Subject: Re: [LINK] RFID and Passoports more misinformation
> To: rchirgwin at ozemail.com.au
>> The reason I ask is this: you have contradicted (probably correctly!)
>> nearly everything the industry likes to put in its "RFID for dummies"
>> stuff that goes to the media. And what we have is a widespread
>> (ubiquitous?) misunderstanding of how RFID works.
>> It would be nice to correct this...
> I'm wondering, if the credit card code stealing devices they
> physically put in ATM machines are being used successfully, would it
> not be somewhat more easy to steal data from RFID chips [embedded in
> whatever you wish - smart cards perhaps?] if there is even a low
> strength signal that is readable and the reader was within the limits
> you say?
No doubt if they can install card skimming device in an ATM to steal
card details ... then they can do the same thing with RFID cards
(proximity cards). So I don't see any different between the two. Noting
that you still need a camera to capture the PIN number being entered for
At this stage I am only aware of RFID based "stored valued cards" being
proposed to replace cash. My understanding these cards may be limited to
the amount of "cash" they hold.
I am not aware of any industry discussion of using RFID for Credit
cards. The next generation of cards coming are based on contact type
"smart card" technology.
More information about the Link