What is RFID and how does RFID tags, RFID readers work

Ever stood in a grocery store queue waiting for your turn before you could pay and get out? Most of us did, and it is a tiresome, irritating task. But soon, these queues could disappear when the bar codes are replaced by smart tags, also known as RFID tags. If you are unfamiliar with Radio Frequency Identification, RFID stands for radio frequency identification.

Radio Frequency Identification or RFID is a technology consisting of radio frequency or waves to transfer data and identify objects.

In technical terms, RFID employs electromagnetic fields to identify tags attached to objects automatically. An RFID system includes a minute radio transmitter and receiver. An RFID tag, which contains information such as the item's price or name, can be tracked and stored for future reference.

What is RFID

Radiofrequency identification uses electromagnetic fields to automatically recognize tags connected to tags. The object, in this case, can range from books in a library to items purchased from the shopping mall or inventory in the warehouse. The application of RFID is not limited to inanimate objects but also living beings such as birds and humans. A radio transmitter and receiver operate together to identify an object and read a tag's information.
what is RFID
Image courtesy – Zina Yonten, Fabacademy

How does RFID work

The technology behind RFID is based on radio waves and computer chips to transmit information. When you think about RFID, it's easy to understand its advantages. Like barcodes, RFID uses radio waves to identify items.

An RFID system has three main components: an RFID reader, an RFID tag, and a transceiver. The reader, or transceiver, transmits radio waves to activate the tag. The tag, also called a transponder, responds to the radio signals whenever this object is in the reader’s range and transmits information to the reader. If the reader is within range of an RFID tag, it will detect and read the information contained within.

RFID technology is quite similar to the one used in a barcode. Although barcode requires the object and the scanner to be in the line of sight, RFID has no such requirements. As long as the object falls in the reader's range, it can recognize and send the feedback signal back to the reader.

What is inside the RFID system

The RFID system contains two components, the RFID tags and the RFID reader. Now, these RFID tags come in three formats which are:

Active RFID: Active tags come with their antenna coil and power source, namely a battery. High- frequency tags are more sensitive to interference. It can be read from up to several hundred meters away. While active tags are the most common type of tag, they can also be implanted in people.

Passive RFID: Passive tags get power from a reader antenna that sends electromagnetic waves to induce a current in the tag antenna. Low-frequency tags use special antennas to enhance signal strength. Passive RFID tags are usually passive because they don't have their own power source. As passive tags lack power supply, their range is less than the active and semi-passive tags. Passive RFID tags are small, thin, and can be attached to a physical object, such as a piece of clothing. The reader sends the energy to the tag, which then modulates the energy with the information it needs to identify it.

Semi-Passive RFID: Semi-Passive tags involve battery-run circuitry and an RFID reader-powered communication channel.
RFID System
Image courtesy – Zina Yonten, Fabacademy

The RFID tag could be an active tech, it could be a passive tech, or it could be a semi-passive tech. They come in many sizes and shapes, from as big as a handheld reader to as large as the shopping mall doors. The RFID reader is composed of three components, which are:

RF signal generator: It generates a radio wave transmitted using an antenna.
RF signal detector: It receives the feedback signal from the tag.
RF Microcontroller: It is used to process the information the RFID tag has sent.
RFID Reader
Image courtesy – Zina Yonten, Fabacademy


RFID tags are devices that transmit information to a central database of data. They can be used in various applications, from inventory tracking to data collection to asset tracking. Let us see the basic components inside the RFID tag. The first component inside the RFID tag is the transponder, which receives the radio waves from the reader and sends the feedback signal back to the reader. Since the passive tags lack their own power supply, they depend on the radio waves emitted by the reader. The capacitor stores the energy from radio waves using this rectifier circuit. This energy is used as a supply for the controller and the memory element inside the RFID tag. The RF signal can be tracked as far as the reader has a line of sight. But most systems are designed to have a limited range.

Most of the tags being used today are passive tags because they are cheaper than active ones, as they do not require any power source, so they are pretty compact.

In the global marketplace, shipments move fast, and port operations must run at maximum efficiency. Manual tracking cannot keep up with the business pace and can become a hassle if disruptions arise. Tags can help inventory management and reduce theft and counting errors. As a result, RFID tags have become an indispensable asset and facility management tool.

Working principle in an RFID system

The RFID tags operate in three different frequencies - the low-frequency range, the high-frequency range, and the ultra-high frequency range. The low-frequency signals travel a very short distance, so the low-frequency RFID tag range is up to 10 CM. The high-frequency radio waves can travel up to 1 meter, while the ultra-high frequency radio waves can travel much longer, like 10 to 15 meters.

The working principle of the RFID tag is based on inductive coupling for low frequency and high- frequency operation. In contrast, in the case of an ultra-high frequency, the working principle is based on electromagnetic coupling.
Inductive Coupling
Image courtesy – Zina Yonten, Fabacademy
Working principle of low-frequency and the high-frequency RFID tags
We know the RFID reader continuously sends a radio wave with a particular frequency. These radio waves that this RFID reader has sent serve three purposes:
  • It induces enough power into the passive tag.
  • It provides the synchronization clock for the passive text.
  • It acts as a carrier for the data coming back from the RFID tag.
The low-frequency and high-frequency operations involve the RFID reader and tag, which are very close. The RFID reader generates a field that couples with the antenna of an RFID tag. A voltage is induced across the coil of an RFID tag because of this mutual coupling. The sum portion of this voltage is getting rectified and used as a power supply for the controller and the memory elements. As the RFID reader emits a radio wave of a specific frequency, the voltage induced across the coil is also of a specific frequency. This induced voltage is also used to derive a synchronization clock for the controller.
Frequency Of Operations
Image courtesy – Zina Yonten, Fabacademy
The current starts flowing through the load when we connect the load across the coil. When we change the load impedance, then the current flowing through this load also changes. This rate of change of current generates a voltage in an RFID reader. Switching the load on and off is called load modulation. When we switch the load on and off as per the stored data in the RFID tag, the RFID reader can read the data in the form of voltage. With this load modulation technique, the RFID reader can read the data.
Working principle of ultra-high frequency RFID tags
Since the distance between the reader and the tag is up to a few meters in the case of ultra-high frequency tags, the coupling between the reader and the coil is far-field coupling.
Far Field Coupling
Image courtesy – Zina Yonten, Fabacademy
The RFID reader continuously transmits radio waves of a particular frequency toward the RFID tag. The RFID tag sends a weak signal to the RFID reader. This weak signal is known as the backscattered signal. The intensity of the backscattered signal depends upon the load matching across the coil. If the load is precisely matched, the backscattered signal's intensity is higher. In case of load mismatch, the intensity of this backscattered signal is less. By changing the load condition, we can change the intensity of this backscatter signal.

The reader can read the data by changing the load condition according to the data stored in the tag. In the case of a far-field coupling, the distance between the RFID reader and the RFID tag is a few meters. So, the initial signal the reader sends should be strong, so the RFID reader can retrieve the backscattered signal. It is how a signal is sent back to the RFID reader using this backscattered modulation technique.

Different applications of RFID

RFID technology is becoming increasingly popular in the manufacturing, retail, shipping, and logistics industries. This technology is transforming businesses and allowing them to track and manage assets more efficiently. Although the RFID tech has been around for decades, it has only recently been made commercially viable. Today, RFID is used in many sectors, from manufacturing and retail to shipping and logistics. Its benefits are countless, and they include everything from tracking inventory to tracking packages.

Here are some applications and benefits of RFID:
  • RFID has great utility in manufacturing. Just-In-Time manufacturing methods involve tracking items along the supply chain using RFID tags to keep track of the items.
  • RFID systems can also help reduce human error in stock-taking, reduce the number of products stolen, and improve security by automatically checking books. It can even provide valuable information to emergency responders in a fire or flood.
  • Another application for RFID is tracking and identifying vehicles. RFID allows companies to keep track of vehicles, assets, and people. It also helps businesses track customers, inventory, and inventory.
  • It can automate processes in a business, improve efficiency, and boost quality. Companies can access real-time data on the individual asset level, providing them with actionable measures.
  • You will be amazed at how much you can achieve by integrating RFID into your supply chain.
  • RFID technology is also used to track livestock. By inserting RFID tags under the skin, these tags can help identify livestock and vehicles.
  • Using RFID technology is an effective way to track assets. It also offers security for companies that want to prevent theft.
  • Warehouse automation uses radio signals to share information. RFID tags can hold varying amounts of information and can be paired with an RFID reader to ensure accurate tracking and management.
  • RFID tags are especially useful in warehouses because they allow companies to respond to customers quickly.
  • RFID tags also help companies improve their processes in warehouses. It helps companies optimize their warehouses and inventory.
  • Many of the applications of this technology include inventory management, supply chain management, and access control.

Issues with RFID

RFID is a technology for tracking products, animals, currency, and other items. Its frequency allows it to process multiple tags at once. However, technology isn't free of challenges. The FCC and ETSI regulate the amount of power emitted by RFID devices. RFID technology also requires databases and systems integration. While RFID technology is generally safe, some types of materials can interfere with its read range. However, metals and liquids are common culprits. RFID tags can't be read through the liquid, so RFID readers are often more expensive than traditional credit cards. But it is still relatively affordable, and many organizations are conducting pilot deployments. Fortunately, new techniques and equipment are being developed to combat these problems. Privacy issues have been raised about the use of RFID technology.

Future of RFID

RFID can be used in nearly every industry. For example, the warehousing and distribution industry has huge quantities of products that need to be tracked. In this scenario, RFID tags can be read using a handheld device, a bar code scanner with an RFID attachment, and a company's ERP system. RFID tags can also be used in retail stores and other industries where high-volume inventory is common. RFID tags make tracking inventory and identifying products easier for these businesses.

The benefits of RFID are largely unsurpassed: greater supply chain visibility, faster production output, and improved security. This technology also can revolutionize many sectors, from retail to the military. With the ability to track every piece of inventory, RFID can save you time and money in various ways. However, it will take a while before RFID becomes a standard tool in our daily lives. For now, it's a promising technology for both companies and consumers.

Networking and Communications, Zina Yonten, Fabacademy.org
What is RFID technology, CuriousPort
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