Information system for smart cards without contacts

Kurzfassung

A Spanish public university has developed a system of reception-emission of information for smart cards without contacts that allows the use of very low frequency fields (below 100 kHz). Thus, the screening problems of present techniques are avoided. The research team looks for collaboration with public or private companies for patent license.

Details

The system is made up of three modules:

- Emitter System. This system consists of a generator of a variable and alternate magnetic field with any frequency minor to 100 kHz and with a null field zone where to locate the receiver system without it saturating.

- Receiver System. A magnetic tuneable sensor is used; it directly detects the alteration of the magnetic field produced by the card when it is tuned at the frequency of the emitter system. In order to avoid saturation of the sensor, it is located in the null field zone of the generator; thus, the sensor cannot detect the field produced by the emitter system but is able to measure other fields of the same frequency but with a phase difference, for instance, the field due to the presence of a magnetic material magnetised by the emitter system.

- Smart card without contacts. When frequency is reduced, the field produced by the circuit of card is null at a very short distance of it, so in principle the system would not be valid. To avoid this problem a magnetic core surrounded by a spiral winding is introduced in the card.

The field produced by the winding is high enough to alter the magnetisation of the core without needing a resonant circuit. This magnetisation can be detected by the receiver system. In addition, the induced electromotive force is used to feed an integrated circuit in the card. This circuit can open and close the winding, modifying the magnetisation of the core and thus being able to send information.

The Group of Magnet devices (GDM) has developed this technology. It is formed by researchers from the Department of Physics and Information technologies from Universidad Politécnica de Madrid. It began in 1979 and today it is composed of 8 doctors, 4 PhD students and 2 undergraduates. The main research and development areas are the following:

• Magnetic sensors (magnetometric, level, density and piezoelectric-magnetostrictive).
• Planar magnetic devices.
• Security systems (tailoring of magnetic materials: magnetic signatures).

Innovative Aspects:
The technology is the only system that allows the use of cards without contacts at very low frequencies, which avoids screening problems caused by induced currents.

Some of its main innovating characteristics are the following:
• It measures the magnetic field produced by the card, not the electromotive force induced by this field.
• A resonant circuit in the very card is not needed.

Main Advantages:
The use of magnetic materials electrodeposited to create the core of the card and the use of PCB (Printed Circuit Board) planar technology in the card and the receiver systems, could suppose a considerable decrease of costs and a simple industrial development thanks to its easy manufacture.

These cards replace low-frequency systems (~ 100 kHz) in applications where screening by induced currents is a problem. They also can replace high-frequency systems (~ 10 MHz). This technology solves the problems of losses by induced currents in present systems.