RFID technology has three elements, including RFID tags, RFID readers, and RFID software. These elements work together to track, manage, and store data about RFID-tagged objects.
RFID tags are small devices that contain a chip and antenna. The chip stores information about the object to which it is attached, and the antenna enables the tag to communicate with an RFID reader. This article focuses on the different types of RFID tags and how they are used.
Before we look at the types, it’s worth defining what an RFID tag is. An RFID tag is a device that stores information about an object to which it is attached. The tag uses radio waves to communicate with an RFID reader, which sends the information to a computer for processing.
RFID tags come in a variety of shapes and sizes, and they can be made from different materials depending on their intended use. Some tags are as small as a grain of rice, while others are larger and more durable.
The architecture of an RFID tag typically includes three main components:
- RFID Chip. This is the smallest component of a tag. It has a memory that can store small amounts of data, primarily the object’s unique identification number. This number can be re-written (only for read/write tags), enabling the tag to be used multiple times.
- RFID Antenna. This component sends and receives radio waves, allowing the tag to communicate with an RFID reader. The size and shape of the antenna determine the range at which the tag can be read.
- Substrate or Housing. This part of the tag protects the chip and antenna from damage. It also determines the tag’s form factor and size. It can be made from different materials, including plastics and fabric.
These elements are typically encapsulated in a single unit, although the antenna may be separate from the chip and housing in some cases. However, they must all be in perfect working conditions for the tag to function properly.
RFID Tag Classification
While there are many different types of RFID tags, they can generally be classified based on:
- Source of Power. This refers to how the tag gets its power. Some tags have a built-in battery that powers the device, while others rely on the energy transmitted by the RFID reader to function.
- Memory Type. There are two main types of memory: read-only and read/write. Read-only tags pre-programmed chip with a unique identification number at the time of manufacture. This number cannot be changed or rewritten. On the other hand, Read/write tags have a blank chip that can be programmed with new data.
- Operating Frequency. RFID tags operate at different frequencies, depending on the specific application. The three main frequency ranges are low frequency (LF), high frequency (HF), and ultra-high frequency (UHF). Each range has its advantages and disadvantages, which will be discussed in more detail later.
Classification Based on Power Source
RFID tags can be classified based on the source of power. The two main types of RFID tags are active and passive.
- Active RFID Tags
These tags have a built-in power source, usually a battery. This enables the tag to transmit radio waves over long distances, typically up to 100 meters.
Active tags are more expensive than passive tags and they require more maintenance. The battery life of active tags is limited, which means they need to be replaced more often.
These replacement requirements and high procurement costs make active tags less popular than passive tags. However, they are still used in applications where long read ranges are necessary, such as inventory management and asset tracking.
- Passive RFID Tags
These tags don’t have a built-in power source and they rely on the energy transmitted by the RFID reader to function. The RFID reader sends a radio wave that energizes the tag and powers it up. The tag uses this energy to transmit its signal back to the reader.
This technology is called inductive coupling. The distance between the tag and the reader determines how much power is transferred to the tag. If the tag is too far away, it won’t receive enough power to function.
Passive RFID tags are more affordable than active tags and they don’t require maintenance. As such, they are more popular than active tags. They are typically used in applications where short read ranges are sufficient, such as event management and supply chain tracking.
Classification Based on Memory Type
RFID tags can also be classified based on the type of memory. As mentioned earlier, there are two main types of memory: read-only and read/write.
- Read-Only RFID Tags
As the name suggests, these tags can only be read and cannot be rewritten. They can be pre-programmed with a unique identification number at the time of manufacture, or programmed later using an encoder.
Once encoded, the tag cannot be modified again. This is because the read-only memory is typically locked to prevent accidental or unauthorized changes.
Read-only RFID tags are less expensive than read/write tags and don’t require special programming devices. They are often used in applications where the data needs to be read but never changed, such as product identification.
They can also be used in ticketing where the data needs to be read, but the ticket cannot be reused. For example, a one-time-use event ticket cannot be copied or altered in any way.
They are usually cheap and available on a large scale, making them more popular for these types of applications. For example, world cup matches have used read-only RFID tags ticketing system to prevent ticket fraud and reduce cost.
- Read/Write RFID Tags
As the name suggests, these tags can be read and rewritten as needed. They have a blank chip that can be programmed with new data using a programmer.
Read/write RFID tags are more expensive than read-only tags and require special programming devices. They are often used in applications where the data needs to be read and updated regularly, such as employee management.
They can also be used in access control where the data is updated whenever a user is added/removed from the system. For example, an employee’s access privileges may be updated when they are promoted or transferred to a different department.
Classification Based on Frequency
This is probably the most vital classification because it determines the read range and other performance characteristics. RFID tags can operate at different frequencies, but the three most common are low frequency (LF), high frequency (HF), and ultra-high frequency (UHF).
- Low-Frequency RFID Tags (125-134.2 kHz)
LF tags have a short read range of around 10 cm (4 inches). They can only be read one at a time since they lack adequate anti-collision mechanisms.
Their data transmission rate is also slow, typically around 10 bits per second. This is because the LF signal has a low frequency which doesn’t carry much data.
LF tags are often used in applications where short read ranges are sufficient, such as livestock tracking (as defined by ISO 14223 and ISO/IEC 18000-2). They are also used in access control and asset management.
Their antennae are made of copper coils around a ferrous core. They are quite expensive to manufacture, making them relatively pricey.
- High-Frequency RFID Tags (13.56 MHz)
HF/NFC RFID inlays/ tags have a short read range of around 30 cm (12 inches) to 1 meter. They can be read one at a time or in groups since they have adequate anti-collision mechanisms.
Their data transmission rate is also slow, around 106 bits per second. Their antennae are made of aluminum, copper, or silver coils with 3-7 coils. There are cheaper to manufacture (compared to LF tags), making them more affordable.
They are controlled by various RFID standards, including ISO 15693 (asset tracking), ISO/IEC 14443 A & ISO/IEC 14443 (MIFARE), ECMA-340 & ISO/IEC 18092 (NFC), and JIS X 6319-4 (FeliCa).
This technology is applied in various areas, including contactless payments, public transportation, access control, and asset tracking.
- Ultra-High Frequency RFID Tags (868 MHz to 956 MHz)
UHF RFID inlays/tags have a long read range of around 1 meter to 10 meters. They can be read in groups since they have adequate anti-collision mechanisms.
Their data transmission rate is fast, making them suitable for large-scale applications. UHF tags are also relatively cheap to manufacture, making them more affordable.
They are easily affected by metal and water, which limits their applications. However, metal- mount RFID tags have been modified to overcome this challenge.
These tags can either be passive or active. RFID UHF passive tags harvest energy from the reader’s signal to power up and communicate. Active UHF RFID tags have their power source, typically a battery.
Whichever the case, these tags have a much longer read range compared to other RFID tags. They can communicate at long distances, making them suitable for large-scale applications such as supply chain management and vehicle tracking.
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