RFID Radio Basics
The following section is a primer on radio waves. If you do not know much about radio, you are encouraged to read it. If you are a radio aficionado, it will seem simplistic; feel free to skip over it.
Radio is a small piece of the "electromagnetic spectrum" that covers all forms of radiation. Other parts of the electromagnetic spectrum that you may be familiar with are cosmic-ray photons, gamma rays, x-rays, and visible light.
The Radio Frequency (RF) area is broken down into a number of "bands" (i.e., grouped frequencies) (e.g., the Very High Frequency (VHF) band covers from 30 megahertz (MHz) to 300 MHz. In the United States, using these bands is governed by the Federal Communications Commission (FCC), including who may use a given band, the power level they may transmit at, and how they modulate the signals. Most other countries have a similar regulatory body. Many European Union countries are regulated by the European Telecommunications Standards Institute (ETSI).
Tools and Traps...
It Hertz So Good
RFs are measured in hertz (Hz). Most of the measurements of radio waves for RFID occur in thousands of cycles per second (kilohertz [kHz]); millions of cycles per second (MHz); or billions of cycles per second (gigahertz [GHz]).
The term hertz is in honor of German physicist Heinrich Rudolf Hertz (1857– 1894), who was a pioneer in electromagnetism. Hertz proved that electricity is transmitted in electromagnetic waves, and his discoveries helped lead to the development of radio.
For RFID, most systems utilize one of three general bands: low frequency (LF) at 125 kHz to 134 kHz, high frequency (HF) at 13.56 MHz, and ultra HF at 860 to 930 MHz. There may be some variation of frequency use, depending on the regulations in a particular locale.
Manufacturers of RFID equipment usually choose a given band based on the physics of the band (e.g., how well the signal propagates in a specific environment). The properties of the band also influence the physical size of the antennas and what power transmission levels can be used. Conversely, physical limitations may influence which frequencies and RF bands are used for a given application. Figure 24.3 shows two different RFID tags and a reader.
Figure 24.3: Two different RFID tags and reader with integral antenna
24.4 Why Use RFID?
In the past few years, RFID has been largely seen as the next technology for pricing at the POS in retail stores. However, it has not replaced bar codes, mainly because the cost of individual tags is expensive. However, with the increased flexibility of being able to perform complete inventory tracking from manufacturer to warehouse to retailer, and with the economic influence of large retail chains, the cost of individual tags will soon become affordable.
Tools and Traps...
RFID Microchips for Pets
The act of placing a passive RFID tag under a pets skin, called "chipping" or "microchipping," has become more prevalent in recent years. A chip the size of a grain of rice is implanted via injection into the skin between the shoulders of the cat or dog. The chip is designed to supplement information used on traditional dog tags.
If a pet is lost and subsequently picked up by the animal control officer, it can be scanned at the animal shelter. If a chip is detected in the animal, shelter personnel obtain the owner information via a database provided by the microchip manufacturer. The owner is then notified that their pet has been impounded.
While excellent in theory, in practice it is not without its pitfalls. Since there are no industry standards for pet tags and readers, different manufacturers are using the same frequencies and encoding techniques. As a result, a scanner that reads chips from a given manufacturer cannot read a different brand of chip. Because of a lack of standardization, a pet was euthanized because the shelter could not read the tags. The detection failed because the shelter used a different brand of scanner than that used by the implanted chip.
Due to concerns about this type of event occurring again, "universal" readers that can read several different brands of chips are being developed and implemented. (For more information go to www.npr.org/templates/story/story.php?storyId=4783788.)