How do RFID's work?

[GhostDoggy]

I get the RF (radio frequency) and the ID (IDentification), but exactly how to those little box tags work such that what appears to be a piece of wire on the back of a sticker, or an enbedded metal tag inside a DVD case can tell exactly what product is leaving the premises.

 

[icarus4586]

My understanding was that the little wire things are obviously passive. At the doors to the store, or wherever, there are RF emitters, and when the signal is reflected by the RFID tag, it's modified in some unique way.
That's my guess though, I've never looked it up.

 

[Mday]

it's a game of marco polo.

the passive tags (active ones can be made) absorb the RF energy coming from an emitter (or group of precisely located emitters), and then emits a signal due to the the antenna on it. that's all. the design of the RFID tag itself lends to the ID, e.g. each different signals can be sent back depending on the geometry of the antenna and the signals being sent by the emitters.

now those tags on DVDs are not RFIDs, those are just RF tags. similarly, those squarish ones in use for decades are not RFID tags either. there are no methods built into those things for identification. but they work on the same principle of absorbing RF energy and emitting a signal.

 

[Stas]

now those tags on DVDs are not RFIDs, those are just RF tags. similarly, those squarish ones in use for decades are not RFID tags either. there are no methods built into those things for identification. but they work on the same principle of absorbing RF energy and emitting a signal.
Thank you for noticing that. RFID are the chips that corporations and commies want you to have in your body to track you down (it always starts with an innovative idea like a replacement of credit cards but in the end they will use it against you) just like an animal.

 

[GhostDoggy]

STas, if I'm kidnapped (hahahahaha), I want someone to be able to track me down and lay waste to the land. MOAB my position and hopefully while the SOB's are with me.

Ok, so its not necessarily the length of wire, but how it actually forms itself that produces a unique identifier. Interesting. I'm surprised no one has made this available in consumer product form, but I guess it would require RF sources to know what the responding signature meant in identification (like a national DB).

 

[irwincur]

Think of a detailed UPC code that can be transmitted to a reciever when it has been activated. These things are actually really cool to use in real world situations. I have walked into a warehouse testing them with a scanner (basically a Pocket PC on steroids) and their inventory popped into the database. Pretty simple.

 

[Matthias99]

I'm surprised no one has made this available in consumer product form, but I guess it would require RF sources to know what the responding signature meant in identification (like a national DB).

You can get scanners yourself that can read standard RFID tags, they're just kind of pricey. Also, unless you know what the tag means, all you get is some random numbers (sort of like a UPC code). It's probably just linked to a record in a database somewhere (that you don't have access to).

A few publicly available things that already use them:

Mobil Speedpass (seen similar things recently from credit card companies).
EZPass/FastLane (NE/Mid-Atlantic tollbooths; no more stopping to pay tolls).
McDonalds has been running trials with it (actually using the Speedpass tags in those states) so you don't have to hand them money at the drive-though.
Some big chain stores (Wal-Mart, etc.) are starting to use them for inventory control on their shipping crates/pallets.

Orwellian fears about using RFID to hunt people down are a little out there, IMO. It's not like you can pick these things up from miles away.

 

[dkozloski]

Think GM PassKeylll+ antitheft system.

 

[imported_bajan]

Originally posted by: dkozloski
Think GM PassKeylll+ antitheft system.

hehe "You can't kidnap me, i'm trackable!"

 

[Matthias99]

Originally posted by: dkozloski
Think GM PassKeylll+ antitheft system.

Ah, I'd forgotten about that. There are a number of higher-end cars that use RFID tags in the keys -- the engine won't start if the RFID tag is not present, so it's impossible to pick or force the lock on the ignition.

 

[Mark R]

Essentially, the RFID tag is a fancy barcode - the main differences being that more data can be stored and that they're easier to scan.

Essentially, the device contains an antenna coil, a capacitor and the RFID chip. In the presence of external RF, energy is absorbed by the antenna and charges the capacitor. Once the capacitor is full, the chip powers up and transmits and transmits its code. Because the RFID device is powered by the reader no battery or other power supply is needed.

A variant of RFID has been used in car keys for a number of years, and are pretty much standard on all new cars. In this use a higher security protocol is used. Instead of simply transmitting the tag's ID number, instead the tag transmits an encrypted version of the number, and changes the encryption every time it is activated. This prevents an attacker from simply reading the ID number and reprogamming a new tag with the same ID.

 

[stardrek]

Hello everyone, first post as you can see.
I would like to clear this up a little bit, being someone who has used these in a lab environment. The information that is sent from an RFID is not based on the geometry of the antenna. The information comes from a small-embedded chip (IC) called a EEPROM (Electrically Erasable Programmable Read-Only Memory) which can have a few bytes of data on it. There is no capacitor either; it gets all the power just from the electromagnetic energy from the reader. It uses a principal very close the electromagnetic induction, which pretty much means that coils of wire can pull energy from electromagnetic fields (transformers work in this way). The wire gets the charge and then sends back a signal with information from the EEPROM in what is called a backscatter signal. Holding the RFID near the scanner provides that electromagnetic field. Hope this helps! Glad to be part of the forums.

 

[gsellis]

Originally posted by: stardrek
Hello everyone, first post as you can see.
I would like to clear this up a little bit, being someone who has used these in a lab environment. The information that is sent from an RFID is not based on the geometry of the antenna. The information comes from a small-embedded chip (IC) called a EEPROM (Electrically Erasable Programmable Read-Only Memory) which can have a few bytes of data on it. There is no capacitor either; it gets all the power just from the electromagnetic energy from the reader. It uses a principal very close the electromagnetic induction, which pretty much means that coils of wire can pull energy from electromagnetic fields (transformers work in this way). The wire gets the charge and then sends back a signal with information from the EEPROM in what is called a backscatter signal. Holding the RFID near the scanner provides that electromagnetic field. Hope this helps! Glad to be part of the forums.

Welcome to the forums and great, accurate first post.

As for the conspiracy theorist... Yeah, right. You would not believe the antennas and output that are required to accurately read tags running through frame on a belt. Especially if they were stacked over each other. But, it would shutdown cellphone service...

 

[Radical Ans]

Originally posted by: stardrek
Hello everyone, first post as you can see.
I would like to clear this up a little bit, being someone who has used these in a lab environment. The information that is sent from an RFID is not based on the geometry of the antenna. The information comes from a small-embedded chip (IC) called a EEPROM (Electrically Erasable Programmable Read-Only Memory) which can have a few bytes of data on it. There is no capacitor either; it gets all the power just from the electromagnetic energy from the reader. It uses a principal very close the electromagnetic induction, which pretty much means that coils of wire can pull energy from electromagnetic fields (transformers work in this way). The wire gets the charge and then sends back a signal with information from the EEPROM in what is called a backscatter signal. Holding the RFID near the scanner provides that electromagnetic field. Hope this helps! Glad to be part of the forums.

A professor at my former University was looking into using that very same principal to harvest power from radio signals. I don't have much information about the project right now but it seems like an interesting idea.

 

[stardrek]

It is actually a very simple process. It is just making a something like a transformer on a larger scale. The principle is called Electromagnetic Induction. You can read about it here: http://en.wikipedia.org/wiki/Electromagnetic_induction

It can be used to power things wirelessly, and has been used for this in the past. The only problem is that it puts out huge eletromagnetic fields.