What are the read and write ranges of such cards—and how can those ranges be increased?
Contactless smart cards are plastic cards (usually the size of a credit card) with an embedded radio frequency identification transponder. The RFID microchip can store a serial number and other information. These chips usually have memory that is rewriteable, and are often able to securely manage data on the chip, as well as access to that information.
The standard air-interface communications protocol used for most contactless smart cards is the ISO 14443 standard, which limits the cards' read and write ranges to approximately 1 foot. This is done to prevent other readers from intercepting the transmission between a smart card and an interrogator.
You could increase the read and write ranges by utilizing a large antenna that puts out a lot of energy—but be aware that this is illegal in most countries. Governments restrict the power output of RF devices to prevent them from interfering with other RF devices.
If you are using a card internally, and are not concerned about adhering to contactless smart-card standards or security, you could create a card that employs a different standard, or a different frequency. For instance, embedding a passive high-frequency (HF) transponder based on the ISO 156893 air-interface protocol would increase the read range to about 3 feet (slightly less for writing to the tag), because that standard does not restrict the read distance for security reasons.
You could also embed an ultrahigh-frequency (UHF) transponder in a plastic card, in order to boost the read range even further. UHF transponders can be written to from a distance of 10 feet or more. However, if the card is going to be used for financial transactions, it would be advisable to stick with the ISO 14443 standard and the limited read range that it requires.
—Mark Roberti, Founder and Editor, RFID Journal