LF RFID Tag
LF tags use near-field inductive coupling to get power and communicate with the reader. They are passive and use less power than HF RFID tags.
The data capacity of time-domain chipless RFID tags can be increased by using dispersive transmission line sections known as C-sections that produce different group delays at different frequencies. This encoding method increases the signal-to-noise ratio.
LF RFID Applications
LF RFID tags operate in the 125 and 134 kHz frequency bands, transmitting data through inductive coupling. They are the most common type of RFID tag and provide a cost effective solution for short-range RFID reading applications such as point of sale/retail, security badges and animal tracking. LF tags do not require a battery and are activated by electromagnetic induction when a LF RFID reader’s antenna is within a few centimeters (or inches) of the tag.
RF identification systems that use LF tags include access control, laundry, asset tracking, animal identification, automotive control as vehicle immobilizers, healthcare and various point of sale applications (such as Mobil/Exxon SpeedPass). LF tags are also used in car ignition systems where an RFID tag is embedded in the key and a reader located around the key slot reads it to ensure the correct ID is present before allowing the car to start.
The deciding factors when choosing an RFID tag for an application include its read range, how it will be powered, and the numbering system that you’ll use to program its memory. Data on a RFID tag can be programmed in either Hex code or ASCII (which consists of numbers and letters based on the English alphabet). LF tags can only store LF RFID Tag up to 8 characters so hex code is the most common choice for many customers.
LF RFID Technology
RFID (Radio-frequency identification) is a technology that enables data encoded in smart labels or tags to be captured by a reader using radio waves. These waves communicate with the tag’s antenna and transmit it to a database that can store and manage the data. The tag’s antenna can also be programmed to trigger a programmable logic controller to take some action, such as allowing access or carrying out a monetary transaction.
LF RFID tags typically operate in the 30 kHz to 300 kHz range, with 125 kHz being the most common frequency. This low frequency has a much slower data transfer rate than a higher frequency, but is less sensitive to electromagnetic interference. LF tags can be read at a distance up to 10 cm from an RF Reader and are typically used in security applications like access control, laundry or animal identification systems. They are also a popular choice for automotive control and as vehicle immobilizers, healthcare and point-of-sale systems like Mobil/Exxon SpeedPass.
LF RFID systems can also be used to monitor environmental conditions. For example, a LF RFID system could be used in waste management to provide incentives for recycling. This could help reduce the amount of waste that ends up in landfills and encourage sustainable practices. In addition, a LF RFID system could be utilized in cities to monitor the health of trees.
LF RFID Readers
LF systems have much lower data transfer rates than UHF and HF, but they work well in environments with metal objects, liquids and thick materials. In fact, RFID transmissions at this frequency can pass through water, animal tissues and some metals – which makes them perfect for tag placement on food animals or in fruit bins where containers are mostly made of plastic.
Unlike higher frequencies, which use radio waves to transmit information between the reader and tags, LF readers and tags communicate using inductive coupling. The reader antenna’s magnetic fields induce voltages in the tag antenna, which power the tagged device and transmit a downlink signal with identification and control commands. Tags can be passive or active, with active tags using a small battery to actively radiate and respond to interrogating radio signals.
Passive LF tags use an internal copper coil with hundreds of turns wrapped around a ferrous core to power on and send downlink signals. These are the most common type of LF RFID tag. The LF downlink signal from the reader is enough to wake up most passive transponders, which LF RFID Tag then send their identification and status. Some active LF tags require a power-on command sent via a wireless communication protocol (typically UHF) to wake up and then respond with their own downlink data, allowing them to perform the desired action like reading or writing to a microcontroller memory.
LF RFID Tags
Radio frequency identification tags come in many forms and types for use with different applications. The choice of form factor depends on the application and environment.
LF RFID tags operate at low frequencies of 30 kHz or less and provide a transmission range up to 10 cm or so. They are able to pass through thin metal layers and are highly resistant to electromagnetic interference (EMI) from other electronics like cell phones and Wi-Fi systems.
The LF RFID tag is inductively coupled to the reader antenna via magnetic fields. These magnetic fields induce voltages on the tag antenna, much like the primary and secondary windings of a transformer. These voltages enable data transfer and power to the LF RFID tag. The LF RFID tag is also powered by a battery, allowing it to function in the field for extended periods of time.
Read range is a major consideration in tag and system selection. Progressively, LF, HF and UHF tags increase the distance at which they can transmit data.
For applications that require a low reading distance, LF passive RFID tags are the best solution. In addition to providing a long read range, LF tags consume less power than other tag technologies and are more resistant to environmental interference. LF tags are available in a variety of form factors including card, glass ampoule, coil, plastic brick and disc.