Star Systems University

What is RFID  (Radio Frequency Identification)?

Radio Frequency Identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information. Some tags are powered by electromagnetic induction from magnetic fields produced near the reader. Some types collect energy from the interrogating radio waves and act as a passive transponder. Other types have a local power source such as a battery and may operate at hundreds of meters from the reader. Unlike a barcode, the tag does not necessarily need to be within line of sight of the reader and may be embedded in the tracked object. Radio Frequency Identification (RFID) is one method for Automatic Identification and Data Capture (AIDC)

RFID tags are used in many industries. For example, an RFID tag attached to an automobile during production can be used to track its progress through the assembly line; RFID-tagged pharmaceuticals can be tracked through warehouses; and implanting RFID microchipsin livestock and pets allows positive identification of animals.

Since RFID tags can be attached to cash, clothing, and possessions, or implanted in animals and people, the possibility of reading personally-linked information without consent has raised serious privacy concerns. These concerns resulted in standard specifications development addressing privacy and security issues. ISO/IEC 18000 and ISO/IEC 29167 use on-chip cryptography methods for untraceability, tag and reader authentication, and over-the-air privacy.

What’s the difference between Active RFID tags and Passive RFID tags?

Passive RFID tags

Passive tags are comprised of three elements: an integrated circuit or chip, an antenna, and a substrate.

The RFID chip stores data and performs specific tasks. Depending on its design, the chip may be read-only (RO), write-once, read-many (WORM), or read-write (RW). Typically, RFID chips carry 96 bits of memory but can range from 2-1000 bits.

Attached to the chip is the antenna, whose purpose is to absorb radio-frequency (RF) waves from the reader’s signal and to send and receive data. Passive RFID tag performance is strongly dependent on the antenna’s size: the larger the antenna, the more energy it can collect and then send back out. Larger antennas, therefore, have higher read ranges (although not as high as those of active tags).

Antenna shape is also important to the performance of the tag. Low- and high-frequency (LF and HF, respectively) antennas are usually coils because these frequencies are predominantly magnetic in nature. Ultrahigh-frequency (UHF) antennas, on the other hand, look similar to old-fashioned TV antennas (“rabbit ears”) because ultrahigh frequencies are solely electric in nature.

The third component of a passive RFID tag is called a substrate, which is commonly a Mylar or plastic film. Both the antenna and the chip are attached to the substrate, which may be thought of as the “glue” that holds all of the tag’s pieces together.

In contrast to active RFID tags, passive tags are usually smaller and less expensive.

Active RFID tags

Like passive RFID tags, active tags have both a microchip and an antenna. The chips, however, are usually larger in size and have greater capabilities than the RFID chips in passive tags.

Active tags have two additional components that differentiate them from passive tags: an on-board power supply and on-board electronics.

The power supply is usually a battery, although it can also be solar. The built-in power supply allows the tag to transmit data to a reader on its own, without the need to draw power from the reader itself like passive tags do. In addition, active tags can be read from distances of 100 feet or more, whereas passive tags can only be read from up to about 20 feet.

On-board electronics may consist of sensors, microprocessors, and input/output ports, all of which are powered by the tag’s on-board power source. The electronics allow active RFID tags to be used in a wider range of applications than passive tags. For example, perishable food products may be tagged with sensors that collect data that can then be used to determine expiration dates and warn the end user that the item may be spoiled. Even though many products have expiration dates printed on them, these dates are valid only if the product is stored under the optimal conditions (temperature, humidity, exposure to light, etc.) for that type of product. Thus, the product may expire before the printed date if it is not stored properly. An RFID tag equipped with a temperature sensor might be able to predict the actual expiration date of a carton of milk, for example, which may be very different from the printed date.

Whether you choose to use active or passive tags in your RFID system will likely depend on both your particular application and your budget. Simple asset tracking that utilizes barcode technology will become obsolete as RFID proliferates through organizations, making them more efficient and better equipped for accuracy.

Why use RFID with vehicles?

Three of the most popular reasons to use RFID with vehicles are access control, vehicle identification, and vehicle tracking.

Access Control – The ability to allow or deny access based on a vehicle having a specific RFID tag is a valuable way to provide a building or parking lot an enhanced level of security. These systems keep out unauthorized vehicles that would otherwise take up space and deters individuals from entering a secure building or lot. Thousands of RFID vehicle access control applications are operative in apartment/housing complexes, secure parking lots, construction yards, etc.

Vehicle Identification – The ability to identify a vehicle and access information about it by reading its RFID tag is a beneficial for companies like car rental agencies, car dealerships, and even car wash facilities. With the addition of software, these companies can pull up car records or purchases by just reading the car’s unique RFID tag. Rental companies and dealerships could have several cars on the lot that are nearly identical, so the unique RFID tag provides them with vehicle identification without trying to find and compare multiple VINs. 

Vehicle Tracking – Tracking a vehicle while it is traveling hundreds or thousands of miles is not a capability of UHF RFID; but, if checkpoints are set up along the route, the location of the vehicle can be estimated based on when it passes each one. This is being done throughout the nation at large truck weigh stations along major interstates. When 18-wheelers are weighed, their RFID tags are read to pinpoint location and can also be used to document the journey. 

How to tag a vehicle

Using an RFID tag manufactured specifically for vehicle tracking quickly narrows down the available options. The next step is to decide where the tag will be located on the vehicle. This will be dependent on where the equipment is setup and at what angle the tag receives the best read rates. Below are the three most common types of vehicle tags.

RFID Windshield Transponders – Windshield transponders are distinguished by their ability to adhere to the vehicle’s windshield with a permanent (destroyed upon removal) or semi-permanent adhesive. This type of transponders are tuned to work best on glass and is placed in the top right or left of the inside of the windshield. These transponders are best read with equipment overhead or to the side nearest to the transponder with the antennas angled toward the vehicle.

RFID Hang Tags – Hang tags are unique because they do not adhere or make contact with the vehicle; instead, they hang from the vehicle’s rear-view mirror. The key benefit to this tag is that it is not as permanent as the other two options and can be removed and stored when not in use. 

RFID License Plate Tags – License plate tags are adhered or mounted on the license plate on the back of the vehicle and are read when the car is moving away from the RFID equipment instead of coming toward it. This directionality will affect the setup of the application because the antennas will need to be angled away from the vehicle to read the tag when it is moving past the equipment. 

What is RFID Market Size?

In 2014, the world RFID market is worth US$8.89 billion, up from US$7.77 billion in 2013 and US$6.96 billion in 2012. This includes tags, readers, and software/services for RFID cards, labels, fobs, and all other form factors. The market value is expected to rise to US$27.31 billion by 2024.