Remote-coupling cards
The term ‘cards with remote coupling’ encompasses smart cards that can transmit data over a distance of a few centimeters to approximately one meter from the terminal. This capability is of great significance for all applications in which data should be exchanged between the card and the terminal without requiring the card user to take the card in his or her hand and insert it into a terminal. Some sample applications are:
–access control
–vehicle identification
–electronic driver’s licenses
–ski passes
–airline tickets
–electronic purses
–baggage identification.
The variety of applications suggests that there are a large number of possible technical implementations. In the preparation of the standards, an attempt was made to limit the number of technical variants, with only mixed success. International standards ISO/IEC 14 443 and ISO/IEC 15 633 cover the ranges of up to 10 cm and 1 m, respectively.

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Figure 3.85 For remote-coupling cards, the ISO/IEC standards distinguish between proximity cards and vicinity cards

Proximity integrated circuit(s) cards: ISO/IEC 14 443
The ISO/IEC 14 443 standard, which is titled ‘Identification cards – Contactless integrated circuit(s) cards – Proximity cards’, describes the properties and operation modes of contactless smart cards with a range of approximately 10 cm. The amount of energy that can be transferred over this range is sufficient to power a microprocessor. In order to allow this type of card to be used with existing infrastructures for contact-type cards, they often have contacts in addition to the coupling components for contactless operation, so that they can be used with or without contacts as desired. This type of card is called a ‘dual-interface card’ or ‘combicard’.
The ISO/IEC 14 443 standard consists of the following parts:
–Part 1: Physical characteristics
–Part 2: Radio frequency power and signal interface
–Part 3: Initialization and anticollision
–Part 4: Transmission protocol.

Physical characteristics
The physical characteristics of proximity cards, which are defined in Part 1 of the ISO/IEC standard for proximity integrated circuit cards (PICCs), essentially correspond to the requirements specified for smart cards with contacts. It is to be expected that in use, proximity cards will be exposed to electromagnetic fields corresponding to those intended to be used for the operation of other types of cards that comply with standards such as ISO/IEC 10 536 or ISO/IEC 15 693. The cards must not suffer permanent damage as the result of exposure to such fields or the environmental stress of normal ambient electromagnetic fields. In order to ensure this, the standard specifies maximum values for stresses due to alternating electric and magnetic fields that the cards must withstand without damage. It is the task of the semiconductor manufacturer to design the chips such that they meet these requirements.

Radio-frequency power and signal interface
Proximity cardswork on the principle of inductive coupling. Operating power and data are both transferred using an alternating magnetic field generated by the card terminal. In the ISO/IEC 14 443 standard, the card terminal is called a ‘proximity coupling device’ (PCD). For the sake of readability, in the following description the more general term ‘terminal’ and ‘PCD’ are used interchangeably.

The transmission frequency of the PCD is set to fC = 13.56 MHz ±7 kHz, with a magnetic field strength H of at least 1.5 A/m and at most 7.5 A/m (effective value). The typical field strength versus distance is shown in Figure 3.86. The range of the system can be estimated from the field strength of the PCD and the activation field strength of a proximity card (PICC). With the typical field strength curve shown in Figure 3.86 and an assumed PICC activation field strength of 1.5 W/m, we obtain a range of approximately 10 cm.

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Figure 3.86 Typical magnetic field strength characteristic of a terminal for proximity cards (PCD)

Signal and communication interface
Two different communication interfaces are defined in the ISO/IEC 14 443 standard, which are designated Type A and Type B. The reason for standardizing two different methods was
not technical, but rather that at the time that ISO/IEC 14 443 was being prepared, various designs from different manufacturers were already in existence. As is often the case with standardization, the differing interests of the persons involved made it impossible for them to agree on a single method, although that would have been technically desirable. The two methods mentioned above were agreed on as a compromise, and they were published as an international standard in June 2001. Even with the already existing methods, it is necessary for card terminals to support both methods in order to achieve full interoperability with all cards meeting the ISO/IEC 14 433 standard, since the cards generally support only one of the two standard methods. While a terminal is waiting to detect a proximity card, it must periodically switch back and forth between the two communications methods. This allows it to recognize both Type-A and Type-B cards. Once the PCD has recognized a card, it continues to use the appropriate communications method until the card is deactivated by the terminal or leaves the working range of the terminal.