One of the main elements of an identification system based on RFID technology is undoubtedly the tag (to find out how an RFID system is made and works, you can read the dedicated article here). However, there are many types of RFID tags because of the many applications of this technology. For this reason, it is essential to understand how tags are made and how they work, what the different types are, and what differences they present. Always be able to choose the best RFID tag for the project you intend to carry out.
How An RFID Tag Is Made
Before focusing on the characteristics of the different types of RFID tags, it is essential to understand how the latter are made and what their components are, specifying that the RFID tags referred to below will be UHF ones (an acronym for ultra-high frequency), that is, they work on very high frequencies. Having made this necessary premise, we can ideally dismantle the tag and see what’s inside. An RFID tag is composed of:
- Antenna: This device receives energy via electromagnetic waves propagated by the reader. Once the waves reach the tag, the energy travels through the antenna inside, activating the Chip or integrated circuit (IC). The antenna transmits the data from the Chip to the reader with the remaining power. This process is called “backscatter.”
- Chip or Integrated Circuit (IC ): it is the heart of the tag. Each Chip is unique; they come in various shapes and sizes. However, they are mainly composed of 4 memory banks:
- EPC Memory Bank: The Electronic Product Code can vary from 96 to 496 bits. It is the identification code of the manufacturing company. This portion of memory can be modified.
- TID Memory Bank: The “Tag ID” Memory Bank is the actual name of the tag. This manufacturing company sets this number, which is unique and cannot be changed. We can have two tags with the same EPC but not with the same TID.
- Reserved Memory Bank: This part of memory contains two passwords. The “Access” one allows you to write on the tag, and the “Kill” one disables the tag forever.
- User Memory Bank: User memory stores additional information about a tag. This part of memory is rarely used. Furthermore, not all types of tags have this part of memory.
The Different Types Of RFID Tags
RFID tags can be classified based on different parameters. The most obvious are the form factor, material, and physical characteristics. We can therefore have:
- Adhesive tags are the most used type. They are usually made of paper and attached directly to the object to be monitored. These tags can be modified, and an encoding or code can be printed according to a customer’s requirement. They are the cheapest tags on the market.
- Plastic tags comprise a layer of PVC or PET that encapsulates the Chip and antenna. They are very resistant to impacts and stress. Most can be applied to iron, which is instrumental in applications where metal objects are traced.
- Ceramic Tag: This tag has the Chip encapsulated in ceramic material. It is also mainly used as an anti-metal tag.
- PEEK/PPS tags: tags made of high-performance thermoplastic materials. They are very robust tags and resistant to shocks and impacts. There are two main types: Acid resistance (extremely resistant to acids and chemical agents) and High Temperature (resistant to temperatures from 180°C up to 260°C). PEEK/PPS tags are used in particular industrial applications; they are the most expensive.
- TPU tags are made of thermoplastic polyurethane. They are usually used on curved surfaces, and they are excellent for pipes. They can also be used on metal.
- RFID bracelets/necklaces: These wearable tags are mainly used for access control, especially at public events (e.g., concerts or fairs).
What Characteristics To Consider When Choosing RFID Tags
At this point, we can review the most important characteristics when choosing the most suitable tag for the RFID project we are creating. The main factors to take into consideration are:
- Size: it must adapt to the object’s size; the more significant a tag is, the more readable it will be from a distance.
- Placement: Where the label will be placed on the tagged object affects its response quality. It is always best to put a tag to be visible to the antenna (there must only be air between the tag and the antenna).
- Angle: For a correct reading, you must ensure the antenna is aimed directly at the label. The more angled the antenna, the shorter the reading range. You can mitigate this problem by adding more antennas.
- Orientation: a tag can be placed horizontally or vertically. Depending on the antenna used and its polarization (circular or linear), it may or may not make reading easier.
Naturally, these are some of the main characteristics of the tags that we must pay attention to before choosing the type that best suits our needs. In any case, these are theoretical guidelines that must constantly be tested in the field. Each environment in which an RFID system is integrated has unique peculiarities. Only through a project created by an RFID specialist, numerous technical tests, and a final test is it possible to find the perfect combination to create the ideal RFID infrastructure.
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