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How do RFID tags work?

RFID (Radio Frequency Identification) is a technology where information is stored in an RFID tag chip. They can be read remotely, without physical contact, using RF energy emitted by the RFID reader antenna. The RFID tag itself consists of a chip and an attached antenna. Using them, it receives the signal and replies back to the reader. RFID tags are very diverse and significantly affect the success of the entire RFID system. They come in different physical forms. reading range, price, method of attachment to the product, etc.

How are RFID tags built?

They have two elements:

Integrated circuit (chip)

 

It is the heart of the RFID tag and all information is stored in it. Some chips can store more information than others. Most UHF tags comply with the Class 1 Generation 2 (ISO 18000-6C) standard and use 96 bits of EPC (Electronic Product Code) memory, which is enough space to store 24 hexadecimal characters (0-9, A-F). However, some tags are more expensive because they have extended user memory to store more information.

Antenna

Its size affects the operating range of the RFID tag. The small size tag has a small antenna, which gives a shorter read range. Larger tags with larger antennas will have a greater read range. In addition, the range of the antenna is greatly influenced by the environment that surrounds it. Water and metal respectively absorb and reflect the radio wave and significantly reduce the effectiveness of RFID systems. As far back as 1830, Faraday discovered that high-frequency radio waves were absorbed by metals. Water, because it is a radio wave conductor, also interferes with the operation of RFID systems.

Forms of RFID tags

Fortunately, there are tags available on the market dedicated to metal applications. Such tags in their design have the chip and antenna away from metal elements by using a spacer. An example would be an “on metal” label. There are also tags that, after sticking to metal, can operate at much greater ranges than traditional ones. In this variant, the metal to which the RFID tag is attached acts as an antenna.

Speaking of the form of an RFID tag, we mean its physical form. Depending on the application, RFID tags come in various shapes and sizes, can be applied to a label or placed in a protective casing.

It is the most basic form of RFID tag. It usually appears as a transparent label with an electronic chip and antenna on it. Depending on the environment in which they are used, an additional protective foil is applied to the bottom of the tag to protect against moisture. The cheapest tags do not have a protective foil and are covered with glue on the bottom and adhere to the surface to which they are glued, ensuring tightness. If the label is to be inserted into the product and will not be glued, we should use a tag with double-sided foil.

Inlay

It is the most basic form of RFID tag. It usually appears as a transparent label with an electronic chip and antenna on it. Depending on the environment in which they are used, an additional protective foil is applied to the bottom of the tag to protect against moisture. The cheapest tags do not have a protective foil and are covered with glue on the bottom and adhere to the surface to which they are glued, ensuring tightness. If the label is to be inserted into the product and will not be glued, we should use a tag with double-sided foil.
It is a paper or synthetic label in which the inlay is pasted. The main purpose of the RFID label is to print it with, for example, a barcode or any other data. Such a label can be programmed with a dedicated RFID printer, which will print and program the tag in an instant. If the programming process is not successful - the printer will print the label in such a way that it is illegible (blurring the data), which is easy to detect. Label type RFID label is not suitable for application on metals. Their special version dedicated to applications on metals is the "on metal" variant, formerly also known as "silverline". was associated with keeping the distance between the chip and the metal, the antenna was connected with an aluminum plate to the metal. These sticker tags have an aluminum backing with adhesive.

Label

It is a paper or synthetic label in which the inlay is pasted. The main purpose of the RFID label is to print it with, for example, a barcode or any other data. Such a label can be programmed with a dedicated RFID printer, which will print and program the tag in an instant. If the programming process is not successful – the printer will print the label in such a way that it is illegible (blurring the data), which is easy to detect. Label type RFID label is not suitable for application on metals. Their special version dedicated to applications on metals is the “on metal” variant, formerly also known as “silverline”. was associated with keeping the distance between the chip and the metal, the antenna was connected with an aluminum plate to the metal. These sticker tags have an aluminum backing with adhesive.
Inlay or label tags are very thin, which makes the transition from traditional labels to RFID tags very easy. Unfortunately, the antenna and the chip are not resistant to mechanical actions - e.g. impacts, tearing, etc. Data from a damaged tag is often impossible to read. Hard tags have a plastic housing that provides much greater resistance to external factors. The antenna and chip inside the Hard Tag can be placed in a thermal shield, which means that they can work at much higher temperatures, e.g. 280 degrees Celsius. Hard tags are used in difficult production environments (moisture, oil mist, heavy dust) or when we are dealing with rotating products . They are ideal for containers or boxes that are returned to the owner. The method of mounting hard tags is much wider than in the case of label. They can be glued, screwed, riveted or welded to the product.

Hard tags

Inlay or label tags are very thin, which makes the transition from traditional labels to RFID tags very easy. Unfortunately, the antenna and the chip are not resistant to mechanical actions – e.g. impacts, tearing, etc. Data from a damaged tag is often impossible to read. Hard tags have a plastic housing that provides much greater resistance to external factors. The antenna and chip inside the Hard Tag can be placed in a thermal shield, which means that they can work at much higher temperatures, e.g. 280 degrees Celsius. Hard tags are used in difficult production environments (moisture, oil mist, heavy dust) or when we are dealing with rotating products . They are ideal for containers or boxes that are returned to the owner. The method of mounting hard tags is much wider than in the case of label. They can be glued, screwed, riveted or welded to the product.

 

Types of RFID tags

 

Depending on how the RFID tags are powered, we distinguish passive and active tags.

Passive RFID tags do not have a built-in power supply. The energy to activate the chip comes only from the wave emitted by the RFID reader. They are much cheaper than active markers and generally have a smaller range (supplied by IBCS Poland).

Active RFID tags are battery powered and actively transmitting a signal. They have a longer reading range and are more expensive due to the cost of the battery and transmitter.

 

Types of memory in RFID tags

RFID tags operating in the UHF frequency band in accordance with the EPC Global Class 1 Gen 2 standard have 4 types of memory:

  1. EPC (Electronic Product Code Memory),
  2. User Memory,
  3. TID (Tag Identification Memory),
  4. Reserved Memory.

The EPC and User memory banks are the banks that “transfer” our information. The other two banks hold control data. User memory, i.e. User memory, is a bank that does not have to be present in the tag structure. This memory is optional and is used in tags where the user requires additional space to store information, e.g. when the EPC bank is too small for him.

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    EPC Memory stores the EPC code or electronic product code. It has a minimum of 96 bits of writable memory. There are tags that have the ability to allocate more bits to EPC memory. Many of them have 128-bit memory, there are also those that have even 496-bit EPC memory. The EPC code from this bank is most often used as a unique tag identifier. This is the first writable bank in the RFID tag.

    User Memory – used if the user needs more memory than available in the EPC bank. Usually it is 512 bit, but there are also RFID tags that have 4k or even 8kB. This is the second writable bank in the RFID tag.

    TID Memory is only used to store a unique identification number assigned by the manufacturer that produced the tag. This part of the memory cannot be changed.

    Reserved Memory – a memory bank that stores the access password and the kill password. Each password has 32 bits. The destroy password permanently deactivates the tag (very rarely used) and the access password is set to lock and unlock the tag’s write capabilities. Most users do not use this memory area unless their applications contain sensitive data.

    How to choose RFID tags?

    When choosing RFID tags, the following should be considered:

    • geographical region where the tags will be used:

      just as with readers and antennas, here too, an RFID tag should be selected in accordance with the frequency that is legally allowed in a given geographical area. In addition, remember that both the reader and the RFID tag should be tuned to the same band. which will allow them to communicate.

    RFID tags for metal

    Metal surfaces will reflect the wave emitted by the RFID reader and cause interference that standard RFID tags cannot cope with. In order to overcome this obstacle, tag manufacturers have created special RFID tags that use an additional layer of material separating the RFID antenna from the metal object on which the tag is mounted.

    It is common to use RFID tags to tag metal surgical instruments, industrial tools, and IT assets such as laptops and servers. Metal RFID tags are also used in industry and production, where metal semi-finished products are identified.

    Due to the fact that many metal objects marked with RFID are exposed to demanding external conditions, the tags themselves must also be resistant to them. There are RFID tags on the market that can withstand high temperatures, are impact resistant, etc.