EAS Radio Frequency Types
Electronic article surveillance (EAS) alarm systems help storeowners to reduce retail shrink. A basic system consists of:
EAS labels or tags
Deactivators or detachers
Electronic antennas
The system is simple and reliable. Active EAS labels are attached to merchandise. The EAS labels are removed or deactivated by clerks when merchandise is properly checked out. Electronic antennas are put at the exits of the store. The EAS system will alarm if someone attempts to leave a store with a product that has an active label on it.
There are several types of EAS solutions available:
AM (acousto-magnetic) systems
RF (radio frequency) systems
EM (electromagnetic) systems
RFID (radio frequency identification) systems
Microwave systems
AM (acousto-magnetic) systems
AM systems have the ability to protect wide exits. They use electronic antennas with transmitters to create a surveillance area where AM labels are detected. They operate at a radio frequency (RF) of about 58 kHz.
AM labels are able to work in the system because the ‘working mechanism’ of the label is made of two materials. The first is a magnetostrictive material. This material shrinks (or restricts) when it is exposed to a magnetic field. When exposed to a 58 kHz radio pulse, the material will resonate (like a tuning fork). Although the human ear cannot detect this ringing, the electronic antenna system can.
The second is magnetic material that will create a bias in the magnetostrictive material depending on the state of the magnetic material. If the magnetic martial is magnetized, it creates a bias that allows the magnetostrictive material to resonates at 58 kHz. In order to ‘de-activate’ the EAS label, you must ‘de-magnetize’ the label.
The electronic antenna consists of a transmitter and receiver. The transmitter sends out a 58 kHz RF signal pulse and the receiver listens for the signal pulse. If the EAS label is active, the transmitters pulse causes the label to resonate. The receiver can detect the EAS labels resonance and sound the alarm.
RF (radio frequency) systems
RF systems have the ability to protect wide exits. They use electronic antennas with transmitters to create a surveillance area where RF labels are detected. They operate at in radio frequency (RF) between 2 and 10 MHz.
RF labels are able to work because they consist of a disposable electronic circuit that is tuned to resonate at a specific frequency. The most popular frequency is 8.2 MHz. The circuit consists of an inductor (L) and capacitor (C) attached to an antenna. When exposed to a radio pulse that matches the ‘tuned frequency’, the material will resonate (like a tuning fork). Although the human ear cannot detect this ringing, the electronic antenna system can.
RF labels are ‘activate’ by submitting them to a strong electromagnetic force. The electromagnetic force charges the capacitor. The charged capacitor allows the LC circuit to resonate at the tuned frequency. In order to ‘de-activate’ the EAS label, you must partially destroy the capacitor. This is done by puncturing the tag.
For typical RF systems, the electronic antenna consists of a transmitter and receiver. The transmitter sends a ‘sweeping pulse’. The sweeping pulse would typically be 0.5 MHZ on either side of the target frequency. If the EAS label is active, the transmitters pulse causes the label to resonate. The receiver can detect the EAS labels resonance and sound the alarm.
EM (electromagnetic) systems
EM systems use electronic antennas with transmitters to create a surveillance area where EM labels are detected. They operate in a mixture of low-frequency magnetic fields in the range of 10 Hz to 1000 Hz.
EM labels are able to work because they consist of a magnetic strip that is tuned to generate a harmonic signal when exposed to a specific magnetic field. The magnetic strip will create a bias depending on the state of the magnetic material. If the magnetic strip is magnetized, it creates a bias that will not allow it to produce the harmonic signal. In order to ‘activate’ the EM label, you must ‘de-magnetize’ the label. Only then will it generate the harmonic signal.
The electronic antenna consists of a transmitter and receiver. The transmitter sends out a mixture of low-frequency magnetic fields in the range of 10 Hz to 1000 Hz. If the EM label is active, the receiver can detect the EM labels harmonic and sound the alarm.
