A RFID uses electromagnetic fields to automatically identify and track tags attached to objects. The tags contain electronically-stored information. Passive tags collect energy from a nearby RFID reader’s interrogating radio waves.
Active tags have a local power source (such as a battery) and may operate hundreds of meters from the RFID reader.
One of the main difference and benefit compared to barcodes is that the tag don’t need to be within the line of sight of the reader, so it may be embedded in the tracked object.
RFID tags are used in many industries:
- a 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;
- implanting RFID microchips in livestock and pets allows for positive identification of animals.
The following video shows how this technology works:
Elements of RFID systems
Tags and smart labels
They consist of an integrated circuit and an antenna. The tag is composed of a protective material that holds the pieces together and protect them from environmental conditions. The protective material depends on the application: employee ID badges containing RFID tags, for example, are typically made from durable plastic, and the tag is embedded between the layers of plastic.
RFID tags can be either passive or active:
- Passive tags are the most used, as they are smaller and less expensive to implement. Passive tags must be “powered up” by the RFID reader before they can transmit data;
- Unlike passive tags, active RFID tags have an onboard power supply (e.g., a battery), thereby enabling them to transmit data at all times.
A RFID reader transmits an encoded radio signal to interrogate the tag. The RFID tag receives the message and then responds with its identification and other information. This may be only a unique tag serial number, or may be product-related information such as a stock number or batch number, production date, or other specific information.
RFID systems can be classified by the type of tag and reader:
- An Active Reader Passive Tag (ARPT) system has an active reader, which transmits interrogator signals and also receives authentication replies from passive tags.
- An Active Reader Active Tag (ARAT) system uses active tags awoken with an interrogator signal from the active reader. A variation of this system could also use a Battery-Assisted Passive (BAP) tag which acts like a passive tag but has a small battery to power the tag’s return reporting signal.
Signaling between the reader and the tag is done in several different ways, depending on the frequency band used by the tag, which also depends on the application. Here some frequency band are listed. Generally, the most common are: