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Lots of people talk about it and many people use it: RFID is a technology that has become indispensable in today’s world. For automatic vehicle identification, RFID is the most common choice. But what is RFID? And how does it work? In this article we tell you all about the basic principles of RFID in combination with vehicle access control.

What is RFID?

Radio-frequency identification (RFID) is a wireless identification technology and utilizes electromagnetic fields to automatically identify and track various objects. Every RFID system consists of:

  • A reader, that is connected to or integrated with;
  • An antenna, that sends out a radio signal;
  • A tag that returns the signal with information added.

RFID for vehicle access control

For gate access control, RFID can be used to automatically identify vehicles and drivers. The ability to allow or deny access based on a vehicle having an RFID tag is a valuable way to provide a perimeter or building an enhanced level of security. These systems keep out unauthorized vehicles that would otherwise take up space and prevents individuals from entering a secure building or lot. RFID technology is therefore perfect to use for secured vehicle access applications, such as highly secured vehicle access at airports, seaports and mines. It’s also relevant for fast and convenient vehicle access to car parks, gated communities, staff parking areas, and campuses.

Okay, but how does RFID work?

RFID Reader and Antenna

The principle of all RFID systems are basically the same: a reader uses an antenna to transmit and receive radio signals. It’s possible that the antenna is integrated into the reader or that one or more antennas are externally connected to the reader. Once an RFID tag gets in range of the reader, it will be activated and starts returning a radio signal.

The antenna transmits radio signals to the tag for multiple functions:

  • To energize tags without battery (passive tags).
  • To send instructions to the tag, for example to perform a secure authentication or to request specific information from the tag of the driver.
  • To receive radio signals from the tag, for example the tag identification number.

Different antenna designs can be distinguished. The antenna design will determine the detection area. For vehicle identification systems a long range directional antenna is very useful. The long read range offers a convenient and seamless experience. The directional antenna enables the system to identify only vehicles in a specific lane and prevent cross-reads from vehicles in a separate nearby lane. If you want to know more about different antenna designs and which you should use, we would like to advise you.

RFID Tags

RFID tags are often placed on vehicles like cars, trucks and buses to automatically identify them and grant secure access to the premises. The tag contains an identification number that can be transmitted back to the reader. It may also contain other relevant information, security codes, keys, etc.

There are three types of RFID tags:

  • Passive tags: tags without power source (no batteries). They are powered by the radio signals transmitted by the reader antenna. This guarantees a long lifetime. These tags use radio signal modulation to transmit information back to the reader. The read range relies on:
    – at which range the tags can still be powered
    – at which range the reader still receives the tag’s signal.
  • Semi-active tags: tags with an internal power source (battery), but with no active transmitter. The tag does not draw power from the reader. It uses backscatter reflection techniques to transmit information back to the reader. This allows for a long read range without the high current consumption.
  • Active tags: tag with an active transmitter and with their own power source (battery). These tags can actively transmit their signal to the reader. This allows for a long read range, but typically will have a limited lifetime compared to passive and semi-active tags.

RFID tags are available in different shapes, such as ISO cards, stickers, buttons, etc. Note that the function is identical independent from its shape. You may choose a tag shape that best fits your application. Nedap offers an extensive tag portfolio with passive and semi-active RFID tags. For automatic vehicle identification systems, Nedap recommends to choose a semi-active or passive windshield tag that supports a long read range, because this ensures a fast, secure and convenient operation.

RFID Frequencies

RFID tags and readers have to be tuned to the same frequency in order to communicate. There are different RFID frequencies for public use:

  • Low frequency (LF) 120 – 125 kHz: Older (less popular) proximity technology based upon inductive electromagnetic coupling.
  • High frequency (HF): 13.56 MHz: Contactless smartcard technology for short range and high security applications.
  • Ultra-high frequency (UHF): 800 – 900 MHz: UHF technology enables low-cost passive tags with long read range.
  • Microwave: 2.45 GHz: long-range identification in combination with semi-active tags.

Understanding the frequencies with its specific characteristics at which RFID systems operate will help you to choose the right Automatic Vehicle Identification solution for your application.

Nedap’s long-range identification RFID portfolio

Nedap is specialist in automatic vehicle and driver identification. With our outstanding expertise in RFID technology, we developed a unique portfolio with high performance long-range RFID (and License Plate Recognition) solutions. As one of the pioneers in RFID during decades, we established an impressive track record of vehicle identification installations worldwide and in many different industries.

Examples of projects where Nedap’s RFID solutions were chosen for automatic vehicle identification:

Curious how our RFID solutions can help in your access control application? We would like to get in touch with you.

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