- Contactless data acquisition in real time, without visual contact
- Simultaneous detection of multiple transponders (bulk reading)
- Resistant to dirt and surface damage
- Option to store and edit data
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 perform. 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
- Error 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.
Frequency ranges of different processes
The transport medium for exchanging data between the transponder and the read or read/write unit is radio waves. Different frequency ranges are used for RFID systems.
|Low frequency (LF)||High frequency (HF)||Ultra high frequency (UHF)||Super high frequency (SHF)|
|Frequency||30 – 500 kHz||13.56 MHz||850 or 950 MHz||2.45 or 5.8 GHz|
|Range||Up to 1.2 m||0.01 – 0.3 m||2.5 m||Up to 300 m|
|Reading speed||Slow||As per ISO standard||Fast||Very fast (active transponders)|
|Typical transponders||Smart labels, transponders in plastic sleeves, card transponders||Smart labels||Smart labels||Large-format transponders|
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 voltage at the transponder antenna. This voltage 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, it is available on the transponder antenna as high-frequency voltage. The transponder uses it by means of rectification for the power supply.
Transponders for industrial identification are also available in a wide range of different designs, such as:
- Smart Labels are identification labels that are mainly applied to plastic film 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
Functional principle of data transmission
Coupling elements such as coils or antennas on transponders and the read or read/write unit facilitate data transmission between the two components.
The read or read/write unit creates a high-frequency, electromagnetic alternating field. If a transponder is located within this field, communication can take place. The induction generates a voltage in the transponder coil. The transponder electronics generate an additional signal from this, which is sent back to the read or read/write unit as a response.
For data transmission between the transponder and read or read/write unit, there are different operating modes.
|Power transmission||Data transmission|
|Full-duplex process (FDX)||Continuous||Simultaneous data up and downlink|
|Half-duplex process (HDX)||Continuous||Sequential data up and downlink|
|Sequential process||Sequential||Sequential data up and downlink|