Logo Leibniz Universität Hannover
Logo: Institute of Microwave and Wireless Systems
Logo Leibniz Universität Hannover
Logo: Institute of Microwave and Wireless Systems
  • Zielgruppen
  • Suche
 

Radio Frequency Identification

  •  

  •  

Radio Frequency Identification (RFID) is a well-known wireless system technology, which is getting more and more important in our daily life. In principle, an RFID system consists of a reader, which is an active device, and a transponder, which is in most cases a passive device. The reader transmits data and power to the transponder by near or far field coupling. Typically, low frequency systems use magnetic coupling between a reader and a transponder coil. At higher frequencies, far field coupling between reader and transponder antenna is accomplished. Due to the different coupling mechanisms, the operating distance is up to a few tenth of centimeters (near field coupling at 13.56 MHz) or a few meters (far field coupling at 868 MHz). These frequencies are the most important operation frequencies of commercial available RFID systems. In both cases, the rectified reader signal serves as supply voltage of the transponder. The communication between reader and transponder is based on different techniques, depending on the communication direction. While the reader uses standard digital modulation of the reader signal (in most cases Amplitude Shift Keying; ASK) the communication in direction from the transponder to the reader is accomplished by load modulation (near field coupling) or backscattering (far field coupling) of the reader signal.

Although there are many commercial RFID systems available; a lot of scientific research is still needed for performance improvement of established systems and for new emerging applications and markets. At the Institute of Microwave and Wireless Systems a research team works on different interesting topics for new RFID applications. In the MIBAR project researchers at the Institute of Microwave and Wireless Systems work in cooperation with Prof. Thomas Kaiser from Universität Duisburg-Essen on a multi antenna RFID system. The project is funded by the Deutsche Forschungsgemeinschaft (DFG). The second project is part of the Collaborative Research Centre 653 (CRC 653), where an interdisciplinary team is involved in applied basic research on so-called Gentelligent components. In our subproject an optically powered millimeter wave sensor transponder, which can be easily integrated into metal, is investigated. The device measures temperature and acceleration, logs all interesting events, and transmits the data to the corresponding reader. The transformation of the scientific results of the CRC 653 into an industrial system is the main challenge in the third RFID project. In this project the advantage of low power wireless communication via backscattering is used for monitoring machine tools used for industrial high speed drilling processes.

Optoelectronic Integration of Radio Frequency Communication Systems in Metal Components

Since 2005 HFT is working on the research of wireless communication systems in the framework of the Collaborative Research Centre 653 (CRC 653) “Gentelligent Components in their Lifecycle - Utilization of Inheritable Component Information in Production Engineering” [CRC653 website]. The objective of this sub-project is to enable a metallic component to communicate with its environment, store and process data during its entire life cycle. For this purpose, electromagnetic waves in the gigahertz range are used.

Wireless Process Monitoring for Industry 4.0

In the idea of the fourth industrial revolution we see a merging of the real and virtual world to one internet of things (IoT). Even smallest devices and machines will communicate with each other or with operators and they are able to organize themselves without the need of any centralized controller. The future-oriented project “Industry 4.0” is aimed to realize this vision in the industry to be well-equipped for production in future.

An excellent example for such an application in production is the equipment of the tools and work pieces with intelligent monitoring systems. This information and communication system consists of a transponder assembled with sensors, called sensor node, and a reading device, via which the data exchange is initiated. The integration of a sensor node in a tool enables an early fault detection and enhances the efficiency of the process chain by an optimal and more efficient use of machines.

Multiple-Input Multiple-Output Radio Frequency Identification

Within the last years the proliferation of RFID systems and technologies has increased enormously. Besides the purpose of identifying goods, e.g. in supply chain management, RFID technologies become more and more important in other scenarios of data exchange, e.g. as an alternative to Bluetooth or ZigBee.

For passive and semi-passive, i.e. battery-assisted RFID tags, the transmission of data between tag and reader relies on the principle of backscatter modulation by varying the mismatch between the tag antenna and its load. Thus, due to its dyadic channel structure, a backscatter system suffers from heavy path loss, which increases with the fourth power of the distance like in a radar system. In multipath environments the system performance is additionally limited by fading effects, which are more severe than in classical "one way" communication systems.

Due to the demand for higher data rates or the extension of the achievable range or reliability, multi-antenna RFID systems with higher frequencies of operation have come into the focus of research, permitting the application of MIMO techniques. Within RFID systems multiple antennas can be used at the reader and at the tag as well. The MxLxN MIMO RFID system can be characterized in the narrowband case with complex baseband channel coefficients for the forward link and the backscatter link.

The multiple antennas can be used for various purposes, e.g. at the receive (RX) array (N>1) for enhancing the reliability or range via maximal ratio combing or for collision recovery of multiple tags. A transmit (TX) array (M>1) can e.g. be used for enhancing the backscatter power of the tag via transmit diversity.

The multi-antenna RFID tag (L>1) is characterized by the LxL signaling matrix consisting of the modulated reflection coefficients at each tag antenna and the internal transmission between the tag antennas. When each antenna is modulated with the same signal and no internal transmission is present, the signaling matrix becomes a scaled identity matrix.

When each antenna is modulated with an individual data stream (without transmission), the signaling matrix is a diagonal one. This type could be used for enhancing the data rate via spatial multiplexing or the reliability via space time coding. In case an additional transmission between the tag antennas is present the full signaling matrix exists.

The MIMO RFID research at our institute includes determination of the individual sub-channels (in order to profit from the channel state information for advanced signaling schemes) system simulation of arbitrary multi-antenna backscatter systems including the effects of mutual coupling, especially at the transponder, and hardware prototyping of multi-antenna transponders and measurements in order to verify our theoretical results.

Optoelectronic Integration of Radio Frequency Communication Systems in Metal Components

Since 2005 HFT is working on the research of wireless communication systems in the framework of the Collaborative Research Centre 653 (CRC 653) “Gentelligent Components in their Lifecycle - Utilization of Inheritable Component Information in Production Engineering” [CRC653 website]. The objective of this sub-project is to enable a metallic component to communicate with its environment, store and process data during its entire life cycle. For this purpose, electromagnetic waves in the gigahertz range are used.

Wireless Process Monitoring for Industry 4.0

In the idea of the fourth industrial revolution we see a merging of the real and virtual world to one internet of things (IoT). Even smallest devices and machines will communicate with each other or with operators and they are able to organize themselves without the need of any centralized controller. The future-oriented project “Industry 4.0” is aimed to realize this vision in the industry to be well-equipped for production in future.

An excellent example for such an application in production is the equipment of the tools and work pieces with intelligent monitoring systems. This information and communication system consists of a transponder assembled with sensors, called sensor node, and a reading device, via which the data exchange is initiated. The integration of a sensor node in a tool enables an early fault detection and enhances the efficiency of the process chain by an optimal and more efficient use of machines.

Multiple-Input Multiple-Output Radio Frequency Identification

Within the last years the proliferation of RFID systems and technologies has increased enormously. Besides the purpose of identifying goods, e.g. in supply chain management, RFID technologies become more and more important in other scenarios of data exchange, e.g. as an alternative to Bluetooth or ZigBee.

For passive and semi-passive, i.e. battery-assisted RFID tags, the transmission of data between tag and reader relies on the principle of backscatter modulation by varying the mismatch between the tag antenna and its load. Thus, due to its dyadic channel structure, a backscatter system suffers from heavy path loss, which increases with the fourth power of the distance like in a radar system. In multipath environments the system performance is additionally limited by fading effects, which are more severe than in classical "one way" communication systems.

Due to the demand for higher data rates or the extension of the achievable range or reliability, multi-antenna RFID systems with higher frequencies of operation have come into the focus of research, permitting the application of MIMO techniques. Within RFID systems multiple antennas can be used at the reader and at the tag as well. The MxLxN MIMO RFID system can be characterized in the narrowband case with complex baseband channel coefficients for the forward link and the backscatter link.

The multiple antennas can be used for various purposes, e.g. at the receive (RX) array (N>1) for enhancing the reliability or range via maximal ratio combing or for collision recovery of multiple tags. A transmit (TX) array (M>1) can e.g. be used for enhancing the backscatter power of the tag via transmit diversity.

The multi-antenna RFID tag (L>1) is characterized by the LxL signaling matrix consisting of the modulated reflection coefficients at each tag antenna and the internal transmission between the tag antennas. When each antenna is modulated with the same signal and no internal transmission is present, the signaling matrix becomes a scaled identity matrix.

When each antenna is modulated with an individual data stream (without transmission), the signaling matrix is a diagonal one. This type could be used for enhancing the data rate via spatial multiplexing or the reliability via space time coding. In case an additional transmission between the tag antennas is present the full signaling matrix exists.

The MIMO RFID research at our institute includes determination of the individual sub-channels (in order to profit from the channel state information for advanced signaling schemes) system simulation of arbitrary multi-antenna backscatter systems including the effects of mutual coupling, especially at the transponder, and hardware prototyping of multi-antenna transponders and measurements in order to verify our theoretical results.