Transponder card
Transponder cards (also contactless chip cards ) combine two technologies for automatic identification and data acquisition : chip cards and RFID .
For some areas of application, contact-based chip cards are not advantageous. Brief interruptions in contact, for example triggered by vibrations, lead to processing errors. These disturbances can also be caused by wear and tear or soiling of the contacts and electrostatic discharges can destroy the integrated circuit inside the card.
These problems avoid contactless chip cards, which are assigned to the classes 'Close Coupling Cards' and 'Remote Coupling Cards' as well as 'Active Coupling Cards'. The technical differences are determined by the industrial standards of data transmission.
Passive contactless chip cards are assigned to remote coupling cards if the distance between the chip card and the terminal varies from a few centimeters ( NFC ) to around a meter (HF or UHF) during data transmission .
It is particularly challenging to accommodate the chip with all functional elements and the antenna in the only 0.76 mm thin card body. The problem of power supply for the electronics can only be solved with batteries for short-term use because of their small volume. The following four tasks must be solved for a contactless card:
- Embossing an inherent identity (possibly already on the bare chip)
- Energy transfer to supply the integrated circuit.
- Transmission of a clock signal.
- Data transfer to the chip card.
- Data transfer from the chip card.
- Registered mail on the chip card.
An essential criterion is the distance between the card terminal and the card. Contactless chip cards communicate with the terminal without galvanic coupling through inductive or capacitive coupling. Writing back is not possible with capacitive coupling according to the known standards.
- Inductive coupling: The transmission takes place via a coil (open transformer), e.g. B. Amplitude Modulation.
- Capacitive coupling: The transmission takes place via conductive surfaces that are integrated into the chip as an antenna.
Comparison of different contactless chip cards
| Close coupling | Proximity Coupling | Vicinity coupling | Vicinity coupling | |
|---|---|---|---|---|
| ISO / IEC standard | 10536 | 14443 | 15693 | 18000-7 |
| Transmission distance | <1 cm | <15 cm | <1.5 m | <1.5 m |
| Reading distance | up to 1 cm | up to 15 cm | up to 1.5 m | up to 1.5 m |
| frequency | 125 kHz - 10 MHz | 13.56 MHz | 13.56 MHz | 868 MHz |
| Data rate | > 1000 kbit / s | ~ 100 kbit / s | ~ 10 kbit / s | ~ 10 kbit / s |
Contactless chip cards are designed for a service life of ten years. Rain, cold, heat, dirt or dust do not pose a problem for the chip card or the reader.
The arrangement of coil and microchip in a contactless chip card is called a transponder or tag . However, the design of a tag is by no means limited to chip cards, but represents just one of the numerous classes for identification with RFID .