LF RFID Tag
LF RFID Tag
The LF RFID Tag operates on the 125 or 134 kHz frequencies and works well in close proximity to metals or liquids. The LF signals are also less likely to be absorbed or blocked by the materials on which they’re affixed.
The chipless tag has a unique dual polarized structure that increases its bit-encoding capacity. It is a completely passive RFID tag that requires no energy source other than the interrogating signal.
Low Frequency
Low-frequency systems function at frequencies between 30 kHz and 300 kHz with most LF RFID tags operating at 125 or 134 kHz. They operate primarily via inductive coupling. The reader’s alternating magnetic field creates a voltage in the tag’s coil which provides the power it needs to transmit data and operate its electronics. The power output from the coil decreases with the square of the distance between the interrogator and the tag.
Unlike higher frequency technologies, which can struggle in moist situations, LF RFID technology is effective in moisture. It works well with metal objects and items containing water, and it can even read the tags behind some types of thin-metal substances.
LF RFID tags are the most commonly used type of RFID tag and can be found in opportunities like glass ampoule (i.e. PET bottles) and animal injectionable tags (such as ear tag for cattle or pigs). It’s also used in automotive control as an automobile vehicle immobilizer, healthcare, point-of-sale applications, etc. Unlike other RFID frequency bands, LF tags are not subject to radio wave interference from wireless telecommunications. As such, they’re ideal for use in the factory floor, warehouse, and other industrial environments. LF tags also have the advantage of being able to communicate with each other over long distances, making them suitable for large areas and buildings.
Short Read Range
The short read range of LF tags makes them suitable for close-range, low speed, small volume data-requirement applications, such as access control (hotel door locks), animal identification and industrial automation. LF is less sensitive to liquids or metals than higher frequencies and works well in harsh environments.
LF is available in either passive or active forms. Passive tags have RFID Keyfob no internal power source and rely on a magnetic field to transmit their response signal to the reader. Active tags use their own onboard transmitter and battery to send out a query signal and switch on their receiving cicuitry when the tag receives energy above a threshold level. These tags give greater read ranges than passive tags, but they also require more maintenance and are more expensive.
Reader configuration can also limit read ranges. For example, a fixed mount UHF reader has more power and a larger antenna than a mobile handheld, so its read range is typically one meter or more. The number of tags in a skid being read at a portal can also impact read range, as the reader must scan each tag multiple times over a relatively short time to collect a reading.
Many people consider the maximum read range of an RFID tag as its primary metric when selecting a tag for a specific project. However, it is important to remember that read range alone does not equate to better performance. More importantly, a tag must meet the needs of your unique business processes.
Low Power Consumption
LF RFID Tags use a small amount of energy to respond to the radio signals received from a reader. They do not require a battery and can operate on very little power. This makes them ideal for applications that involve sensitive information, such as access control, livestock tracking and as an alternative to key cards in automobiles.
The RF signal that powers the RFID tag’s microchip comes from the reader via inductive coupling. It’s then converted to DC in a harvester circuit. The voltage at this point can vary between 1 V and 1.8 V, depending on the tag IC, antenna inductance and Q factor as well as the base station field strength.
In addition to the harvester, the LF RFID chip contains a charge pump and a control circuit that reduces programming and erasing voltage to lower the power consumption of the EEPROM. This also allows the RFID IC to utilize a smaller EEPROM with higher capacity.
Another benefit of LF RFID tags is that they are less susceptible to interference caused by metal objects and liquids than other types of RFID. This is because LF frequencies have longer wavelengths that can easily penetrate objects and can even pass through water. The only downside to this is that LF tags cannot be read as well from very close distances as HF and UHF RFID tags can.
Inductive Coupling
Low-frequency tags use inductive coupling, a communication technique that relies on the mutual inductance of coils to transmit power and data. The RFID reader’s antenna coil produces a magnetic field that interacts with the conductive antenna of the tag, inducing a voltage in the tag circuitry. This allows the tag to receive the data from the interrogator and respond accordingly, whether it’s a read or command.
The RFID tag’s conductive antenna is tuned to the frequencies of the electromagnetic waves emitted by the RFID reader’s coil. LF RFID Tag The magnetic field produced by the RFID reader is strong in the near-field, but as you move farther away from it, the magnetic energy rapidly decreases. Eventually, the tag’s coil becomes sufficiently irradiated that the induced voltage no longer generates a current.
The LF tag’s circuitry can then create sideband frequencies by varying the load on its antenna, which can be detected by the RFID reader. This is how a grocer’s meat case can be used to read a ham behind aluminum foil—HF would need the LF tag to communicate through the foil in order to do so. This is also why LF has the advantage over UHF in moist environments: the LF radio wave is less affected by water absorption.