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RFID is a technology that uses radio frequencies for the automated identification of objects, people and animals. RFID is in fact the acronym for Radio Frequency IDentification. With RFID technology, identification can be done automatically, massively, quickly, and even at a distance of several meters. Identification is performed through passive RFID tags, an RFID reader (with at least one antenna) and generally a software. These elements make up what is called an RFID system.

 

Operating frequencies

Before going into the details of how an RFID system works, please note that there are different RFID operating frequencies. On RFID Trade, we deal with RFID UHF. For completeness, below are the 4 main standardized categories.

  • 125/134 kHz - RFID LF (Low Frequencies)
    Reading distance of a few centimeters and low baud rate.
    Mainly used in animal identification, but also in vending machines, alarms, access control.
  • 13.56 MHz - RFID HF (High Frequencies)
    Reading distance of a few centimeters (up to 10) and baud rate low/medium.
    This specific frequency is also called NFC (Near Field Communication). Most of the current smartphones are equipped with an NFC sensor.
  • 860-960 MHz - RFID UHF (Ultra High Frequencies)
    Reading distance that reaches several meters, still using passive tags; great baud rate.
    Widely used for logistics, inventory, timekeeping, access control.
  • 5.8 GHz - RFID SHF (Super High Frequencies)
    The highest RFID frequency range. It only includes active tags, therefore with an internal battery, which can reach a detection distance of hundreds of meters.

 

RFID Tags

An RFID Tag is a chip connected to an antenna that increases its reading distance. The most common format of RFID Tags is a label, also called wet inlay. But RFID Tags can be integrated into stronger casings, as well as into badges, or bracelets, or many other items.

Generally, RFID Tags are passive: this means that they do not require a power supply. Instead, they are powered by an RFID reader that, through electromagnetic solicitation, detects them, reads them and, if necessary, programs them. There are also active tags and semi-passive tags, equipped with internal battery which increases the reading distance, but they are not very common.

RFID Tags come in many shapes, sizes, read ranges, operating frequencies, and more. Since there are so many variations and possibilities, you need to narrow your search as much as possible to find a Tag that meets the requirements of your application. In this regard, we recommend that you consult the RFID Tag Selection Guidance.

 

RFID readers

An RFID reader is the centerpiece of the RFID system and is required for any system to function. Readers are devices that transmit and receive radio waves to communicate with RFID Tags. RFID readers are generally divided into two distinct types: fixed RFID readers and mobile RFID readers.

Fixed readers remain in one location and are typically mounted on walls, desks, portals, or other stationary locations. Mobile readers are handheld devices that allow flexibility when reading RFID Tags while still being able to communicate with a host computer or other smart device.

Among the fixed readers, there are readers with integrated antenna and readers that can be connected to external antennas. With these ones, it is possible to cover a larger area, or to develop applications that also rely on which antenna reads an RFID Tag (for example, input/output).

In general, you can connect 1 to 4 antennas to a fixed reader. With special switches, or Antenna hubs, you can connect up to 32 to a single RFID reader. The antennas are connected to fixed readers using coaxial cables, with different types of connectors and with different lengths, as needed.

 

RFID Chips' Memory

Each RFID Tag is equipped with a chip that contains different types of memory.

 

1. EPC memory

The EPC memory is rewritable and is designed to contain the Electronic Product Code. The EPC memory can however be programmed with arbitrary codes. Depending on the manufacturers, the RFID Tags are supplied with an empty EPC, or programmed EPC, with a fixed or pseudo-random value.

 

2. TID memory

The TID is the Tag's Identifier, which is the unique identification code of the chip. This memory is not rewritable. The code is assigned directly by the manufacturer and no one can change it. TID memory is the simplest way to build an RFID solution, as each TID is different. By associating a TID with a single item, there is no need to program the EPC, saving you a step.

 

3. User Memory

The user memory is rewritable, but not all the RFID Chips have it. It is used in those applications in which the EPC memory is not enough to contain all the information. Consider it as an additional memory. The size of the user memory varies according to the type of chip, from a minimum of 32 bits up to a maximum of 2 kbit. This memory is the second one editable by user.

To bettter choose the chip, we recommend to consult the technical characteristics of the RFID chips.