RFID technology

RFID stands for Radio Frequency Identification and means that objects can be identified without physical or visual contact. An RFID system consists of a transponder and a read or read/write unit. A range of different RFID systems are available on the market. However, all share three common properties:

• Clear marking of components or objects
• Contactless and wireless identification of the marked component or object
• The marked component or object only sends its data following a request from the read or read/write unit

With this in mind, there are certain basic functions that every RFID system must fulfil. Depending on the area of application, the RFID systems can offer a wide range of additional functions.

• Identifying transponders
• Reading transponder data
• Managing multiple transponders simultaneously
• Fault detection for safe operation

RFID system types

• Read-only systems: Read unit and transponder, which are only described with an initial ID number. To assign further data to these RFID transponders, it is necessary to link the ID number to the corresponding information in a database.
• Read/write systems: Read/write unit and transponder, containing their own memory. The internal memory in the transponder is implemented in different ways. The read/write unit reads this memory and can also rewrite it.

There are two basic types of RFID transponders: Active transponders have their own energy supply. They are only activated if a read or read/write unit sends commands within the transponder range.

Passive transponders are supplied with energy from the read or read/write unit. This energy supply can come from an inductive coupling or through the backscatter method. In inductive coupling, the electromagnetic field of the read or read/write unit induces a current at the transponder antenna. This current is rectified in the second step.

Systems with high ranges often use the backscatter method. For this, both the transponder as well as the read or read/write unit require a dipole antenna with resonance behavior for the respective frequency of the RFID system. If the antenna on the read or read/write unit emits transmission power, this is available on the transponder antenna as high-frequency current. The transponder uses it by means of rectification for the power supply.

Transponders for industrial identification also exhibit a range of different designs, e.g.:

• Smart Labels are identification labels that are mainly applied to plastic slides or paper
• Transponders in plastic sleeves are used in robust applications with high demands in terms of moisture resistance
• Card transponders are embedded in plastic, e.g., in bank card format