2-32 Theory of Operation
Non-Contact Smart Cards
Types of Cards
Whenever a new technology is developed by multiple manufactures, there tends
to be multiple protocols for the device. For example, during the 1980’s there were
as many personal computer types as there were manufacturers. In time, the
number of computer types dwindled as designs were standardized. The same is
true with smart card technology, except there still exists many off-standard card
types.
The primary information in this section is geared toward the ISO/IEC 14443
Type-A and Type-B cards. However, recognition should be given to a few other
formats that are still widely used.
The photograph on page
2-29 shows a combicard with both a 125kHz antenna
and the standardized 13.56 MHz antenna. This card is used to help facilitate the
transfer from the 125 kHz system to the common 13.56 MHz system. The lower
frequency format is not supported by any of the ISO/IEC standards. These low
frequency cards are frequently referred to as Wiegand cards, and generally only
provide a unique ID when energized.
The FeliCa card format was developed by the Sony Corp. and is similar to the
standard Type-A card, except it uses 212 kb/s data rate instead of the
standardized 106 kb/s data rate. There are also some variations on the
modulation protocol.
The Mifare card is fairly common because it is based on an open standard used
by many manufacturers. According to the Phillips Corporation this format is
fully compliant with the ISO/IEC 14443-A standard.
Communication
Communication with non-contact smart cards is slightly more complicated
because there is no physical connection between the interface and the card. The
card reader sends out a radio frequency broadcast, which not only provides
power to the card, but also establishes communication. This is called inductive
coupling, and is similar to the function of a transformer.
Inductive coupling works the same way as a transformer does, except that the
two coils are farther apart (called loosely coupled). The operating field of the
card reader has a frequency of 13.56 MHz. This is called the carrier frequency.
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