RFID (radio frequency identification) is an automatic recognition technology that uses wireless communication. Generally, a system or a part that uses an IC tag to identify or control various items via wireless communication is called RFID. Here, a description is given mainly of the features of RFID and the principle of wireless communication to provide basic knowledge concerning RFID.
Features
Data can be read at long distances.
Wireless communication allows data to be read at a distance of several meters. Data can be read from a tag that is in a high, relatively inaccessible place. Inventory count in a large store or a storehouse can be easily done while securing operators’ safety.
Multiple tags can be read at once
RFID obviates the need to hold each item to read the data. It enables the data in all tags to be read at once by simply passing the scanner over the tags. This greatly reduces the time required to carry out stocktaking, etc.
Data can also be read from outside the box.
Since data is communicated via radio waves, it can be read from outside the packing box without opening the box, even when a tag is attached to the product. Unlike barcodes, which can not be read when the surface is damaged, RFID is highly immune to dirt and can read data without problem even if the surface of the tag is dirty.
Long life
A passive-type RFID tag can be used semi-permanently without a battery. In addition, because the tag contains a memory, the data can be rewritten. Compared to barcodes, RFID contains and exchanges a much larger amount of data.
RFID frequency bands
RFID technology consists of four frequency bands, the LF band, HF band, UHF band, and microwave band. Murata’s RFID uses HF and UHF band communication among the four frequency bands. Since international compatibility is guaranteed by the ISO/IEC 18000 series wireless communication standards. Our RFID products are used throughout the world.
LF Band
The LF (Low Frequency) band employs an electromagnetic induction method and has a long history of use compared to other communication bands. One example of an application is wireless communication in a keyless entry system for an automobile. Although the read range is only several tens of centimeters, it is necessary to use many windings on the antenna, making it difficult to fabricate a thin, compact antenna.
HF Band
The HF (High Frequency) band exchanges data using an electromagnetic induction method. The HF band requires much smaller winding on the antenna than the LF band, making it easy to fabricate a thin, compact antenna. The communication distance is relatively short because the HF band uses 13.56 MHz, a frequency in the short wave band. Therefore the HF band is suitable for applications in a proximity area, such as those in which persons and items are validated in a 1-to-1 ratio. An NFC (Near Field Communication) device, which is applied for electronic money such as transportation IC cards, also uses HF band RFID.
Microwave Band
The microwave band uses the frequency of 2.45GHz, which belongs to the UHF band. Since this band includes the ISM band, which is also used by microwave ovens and wireless LAN (Wi-Fi), there are concerns about radio wave interference. It is, therefore, necessary to take preventive measures. Also, the communication distance is only 2 to 3 meters which is much shorter than that of the band between 860 to 960 MHz.
UHF Band
The UHF (Ultra High-Frequency) band employs an electronics field-type communication method. The frequency range is between 860 and 960MHz, making the UHF band suitable for applications that require a communication distance of several meters to read multiple sets of data simultaneously. Most stock control and automatic inspection is carried out using this frequency band.
Table 1. RFID Frequency Bands
Principle of RFID communication
RFID communication is performed when a battery-free passive tag reflects carrier waves sent from the reader/writer.
Flow of communication
- The reader/writer transmits radio waves.
- The antenna inside the IC tag receives radio waves from the reader/writer.
- Electric current flows through the IC, converting the data in the chip into signals.
- Signals are transmitted from the antenna, which is electrode-printed on the IC tag.
- The antenna in the reader/writer receives signals returned from the IC tag.
- Data is processed by PC via the reader/writer controller.
Figure 1. Principle of RFID communication
