RFID (Radio Frequency IDentification) – how it works

A Visa credit card with the RFID symbol

Kathy posted an excellent Noxious Rant yesterday titled, “Chip Technology and Credit Cards.” This piece explores the technology a little further.

We’re seeing the term “RFID” popping up more often in the news lately. It’s an acronym for “Radio Frequency IDentification” and has been used in various forms for a number of years.

RFID is a generic term for technologies that use radio waves to automatically identify people or objects. There are several methods of identification, but the most common is to store a serial number that identifies a person or object, and perhaps other information, on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID tag).

An RFID system consists of a RFID tag and a reader.

The reader sends out electromagnetic waves. The tag’s antenna is tuned to receive these waves. The reader converts the radio waves reflected back from the RFID tag into digital information that can then be passed on to computers that can make use of it.

A passive RFID tag draws power from the electromagnetic field created by the reader and uses it to power the microchip’s circuits. The chip then modulates the waves that the tag sends back to the reader and the reader converts the new waves into digital data.

The ancestor of the modern RFID was patented in 1973, but the first patent associated with the abbreviation “RFID” was granted in 1983. So, the general technology has been around for a while. But the key to widespread use has been the miniaturization of the tag and (to a lesser degree), the reader.

Some of the original uses for RFID were expected to be in the fields of transportation, banking, security, and medical history. In those days, no one had yet anticipated the possibilities available in retail commerce.

RFID tags can be passive or active. An active tag has an on-board battery and automatically transmits its ID signal. A passive tag is cheaper and smaller since it carries no battery – it depends on the radio energy transmitted by the reader for power. Tags for different purposes also operate on different frequencies and have different costs, transfer rates, directionality, and susceptibility to interference.

As noted before, the miniaturization of the RFID chips is what has expanded the horizon for the technology, but while the chips themselves have been reduced in size, the antennas are beginning to be a limiting factor.


Small RFID chip, here compared to a grain of rice

Hitachi is the current record holder for the smallest chip, at .05mm x .05mm. The dust-sized chips can store 38-digit numbers. A major challenge is the attachment of antennas, thus limiting read range to only millimeters for that tiny chip.

Speaking of range, the question naturally follows: what is the range at which a chip can be read by a reader? The answer is that it depends on several factors, not the least of which is the frequency at which the system operates. The read range of passive tags (tags without batteries) in general will be a foot or less. High frequency tags are read from about three feet and UHF tags are read from 10 to 20 feet.

An application such as tracking railway cars requires reading at greater distances and uses batteries to boost read ranges to 300 feet or more.

And finally, here is one of the FAQs on the RFID site that I found interesting: “Will governments be able to use RFID to spy on people?”

And their answer was: “If companies choose to put RFID tags in clothes and items consumers carry around, such as wallets, and consumers choose not to kill the tags in these items, it might be possible for governments to use RFID tags for surveillance.

But they would have to have access to the database of information related to the tags’ EPCs, and it would be easy for individuals to avoid being tracked. RFID readers must emit radio waves to read tags. The signals from a reader can easily be detected and blocked.”

OK, got that? Applying the technology available today, it’s not really feasible; it’s possible, but not feasible. But (and that’s a big BUT), how about 20-30 years from now, when battery and chip technology and miniaturization has evolved? And access to a database of information? Ever hear of the NSA?

So I’m just a little bit paranoid; I guess I can remove my tinfoil hat now (and slip into my tinfoil coveralls) because I just KNOW that they’re after me.

If you’re interested in reading more about RFID, check out the FAQ section of the RFID Journal site HERE.


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9 Responses to RFID (Radio Frequency IDentification) – how it works

  1. I.R. Wayright says:

    Did you ever buy something, say a $40 package of triple edge razor blades, and then find a small plastic piece glued somewhere on the inside? If you took that plastic bit apart you’ll find a small silver metal strip inside. That is for inventory control and theft control. It uses RFID technology and when you pass out of the door of the store you are walking through an RFID reader. If that strip didn’t make the cash register go “doot” when it was passed over the window it will activate the warning horns. That window is supposed to register the selling price and disable the strip from triggering the alarms.
    Now, let’s say a thief knew his way around this tech and peeled that strip off a box and left the store with the item he wanted to steal. If he threw that strip on the floor and it stuck to your shoe, you would trigger the alarm when you innocently walked out. So they haul you off to be interrogated, hand cuffed and strip searched until they find the strip.
    Not all products have the strip, but higher priced, easily concealable things may. They will be installed by the manufacturer well inside the packaging. You know how hard it is to open some of the plastic encased goods you buy. Now you know why.

    • Garnet92 says:

      You’re right I.R., more and more items are being “chipped” and the technology isn’t going away – in fact, it’s being improved as we speak. I think it’s entirely appropriate to look at where cellphones were just a few years ago (remember the “brick”?). And that same progress at miniaturization will, no doubt, continue – maybe at an even faster pace. Imagine a “chip” the size of a grain of dust and able to be attached or implanted into darn near anything????

      It’s scary when you’re worried about government intrusion.

  2. Kathy says:

    The thing about technology is that it never stops advancing. Look at the changes just since the 70s and however far we’ve come, they’ll continue for years to come, and sometimes at even faster rates.

    There’s a picture that’s been circulating for some time now of a guy holding a jam box, an old huge cell phone, a transistor radio and several other objects that were huge innovations in their time, but now all those tools are combined in a cell phone the size of your hand.

    I don’t think we’d be talking about the government spying on us if 9/11 hadn’t turned this country upside down. That seems to be when they started taking a much closer look at possible terrorists, and since then O has taken it to even greater levels. If it’s possible, they’re doing it.

    • Garnet92 says:

      And if we, the public, has access to the information I posted above (and more), just imagine what is still deemed too “sensitive” for us to know. I’ve no doubt that our government is looking at ways to use the technology – mostly for good, but history shows us that some will use it for evil.

  3. Clyde says:

    At least if you wear your tin foil coveralls you’ll disable MOST RFID chips. Good post, Garnet.

  4. upaces88 says:

    I graduated from High School in 1965. George Orwell’s 1984 was fiction, right?
    He talked bout this and a lot more.
    This is highly disturbing.
    We are living in a time that he KNEW was going to happen; OR, he was a visionary.???

  5. vonMesser says:

    There was an article a year or so ago in which one of the people involved had a reader of some sort that was able to snag the RFID information from cards at a range of about 15-20 feet. He stood near the door of one of the hardware stored and snagged a large number of card info in an hour or so. Did the article, and then pet people know he had “made” them. It was up on You Tube for a while – mkight still be there.

  6. Garnet92 says:

    Yeah upaces, it was “supposedly” fiction when he wrote it, but it is becoming more and more true. Visionary or seer, who knows? Like you I find it disturbing to think of what our future might be if we continue to follow Orwell’s storyline????