RFID stands for Radio Frequency Identification. These tags are used to identify products or storage much like a barcode system. The tags work by storing information and when an RFID reader reads the tag, the data is transferred through radio waves. So you can have millions of tags that work with one reader.
RFID tags have an advantage as they can store more information than a barcode and the reader does not have to see the tag to read it. RFID tags need at least three general components; antenna, RFID chip, and a substrate. Each tag will need memory which will be on the RFID chip.
ID cards or chips
There are two types of tags active and passive RFID tags. Active have their own separate power via battery or solar-powered and passive is powered by the reader.
Passive RFID Tags
Passive tags are used more often than active tags. These tags are meant to be less expensive so that replacing them is not such a burden. Used often in rugged environments these tags can be built tough but also easy to replace. With the minimum amount of components used these have a higher life expectancy compared to active tags. Since there is no need for external connection these can be made totally sealed in a single housing.
Active RFID Tags
With the power supply onboard these tags can constantly transmit and do it at larger distances than passive tags. Using an active tag means it can transmit data to a fixed reader on its own. Active tags have more capabilities as sensors and input/output ports can be implemented. With the extra components, the active tags are built larger than passive tags. Also, the added components mean more expense.
The readers can be portable or in a fixed position. A good example of a fixed RFID reader would be on a conveyor system where it reads tags as they pass the reader. Portable work the same as barcode scanners and can be used by individuals to locate a certain target. Generally, the tags will be used with the corresponding reader the company has for that tag.
What effects the read range?
There are many factors involved with the read range. RFID companies give a max range which is more than likely based on a straight line of travel from the reader to the tag with no interference. We know that in the real world the tag and reader will not always be in-line. If the tag is on metal it has been found to be harder to read at long distances. Other obvious situations such as the tag are on the back of the device or there are objects in between, will play a role. Radio waves can bounce off walls and surfaces, especially metal, and eventually find its target.