Radio Frequency Identification (RFID) is frequently used on a daily basis, without us even realizing it, in various and varied fields of activity. It makes it possible to convey data, to memorize them and to retrieve them remotely thanks to radio waves. RFID is often used for product identification and the automatic collection of information on items, without any physical connection, unlike other technologies such as gencode for example. It can be declined mainly in two different ways. It is then a question of active RFID or passive RFID.
Basic principle of RFID
The basic systems of RFID are made up of several components. Among them, the tag, also called “radio tag“, composed of an electronic chip for identification and data storage, an antenna, used for communication, and a reader or interrogator for the transmission and reception of waves. A computer and software are also required for data storage and analysis. Depending on the type of radio tag used, no battery or battery is required (passive tags), a battery may be needed only for the emission of the wave (semi-passive tags) or to power the tag and for the emission of the wave (active tags).
The RFID tag is a fundamental support of electronic identification. It is often composed of two main elements: an antenna, receiving the waves, and an electronic circuit, in charge of processing and storing the information. In other words, it houses an identifier and data on a chip, itself connected to the antenna. The tag thus exchanges data with a reader via radio waves. Widely used in RFID, the tag is very useful to meet traceability requirements, for example, since it does not necessarily need to be seen to be detected and, therefore, read.
The reader is an electronic device used for transmitting and receiving electromagnetic waves. It detects and recognizes the tag’s identification information through the identifier provided by the chip manufacturer. It is also able to decode the information carried by the incident wave thanks to a decoder.
The RFID antenna can capture and emit electromagnetic waves. The frequency of emission depends on the type of antenna, its length and the frequency set in the chip. Depending on the desired application, the antenna should be inexpensive, non-invasive and as environmentally friendly as possible. In order to maximize energy transmission, the impedance of the antenna must be equivalent to the impedance of the electronic chip contained in the tag. In most cases, this impedance has a value of 50 omega.
The computer and software are used to store the information collected by the reader. In some situations, they may also control the player.
Basic RFID Operation
First of all, it can be a question of active RFID. In this first case, the tags are powered by an embedded energy source. It can be a battery or a cell, for example, allowing the operation of the tag and the emission of its data.
Active RFID can be applied to several sectors of activity, in construction, public works and security as well as in home automation for example. The active tags are largely used for monitoring physical quantities (temperature, humidity, movement). This is particularly the case for the control of the cold chain in refrigerated trucks. They also allow the identification and tracking of people for safety on construction sites. Finally, they can also be used for access control or automatic identification of goods.
- Major asset: high range distance.
- Ability to store a lot more information than passive tags.
- Tags with many extra features.
- Fast transmission rate.
- Large number of labels that can be read simultaneously.
- The cost of the tags is expensive and their lifespan is limited.
- These tags are relatively intrusive since they are of average size and therefore visible.
Active tags have a very long range of up to 500 m. Other technologies, which we will refer to later in this blog, extend this distance to the kilometer.
In a second case, it is passive RFID. Unlike active tags, passive tags do not contain an on-board power source. Instead, they rely on the wave emitted by the reader to power their chip, modulate the signal and, by backscattering, transmit the signal to the reader.
- Low costs.
- Time saving.
- The use of flexible materials. Indeed, being sometimes made of paper or fabric, the tags are less polluting for the environment (provided that the metallic ink for the antenna is as well obviously).
- Significant properties such as their small size, light weight and long service life.
- Few labels can be read simultaneously in this system.
- Their range and reliability remain far less than those offered by active tags and their greater fragility.
The passive tags have a range spread over 3 levels.
- We are talking about short distance with a Low Frequency, when we refer to the contact at only a few centimeters.
- The average distance is a few centimeters to 1m. It is then High Frequency. The NFC for example has a reading distance of 10 cm in the general case.
- Finally, the maximum distance extends up to 15m and uses Ultra High Frequency
Some studies even evoke a third type of RFID: the semi-passive one. Less known of the general public and consequently less used, this device borrows characteristics of the active RFID (the presence of a battery on the tag, to feed it only this time) and properties of the passive RFID (concerning the system of emission). The lifespan of these tags is higher than an active tag and their cost is less important. They remain however more expensive than passive ones.