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Microwave system

Belongs to:

Electronic Article Surveillance

Description:

A microwave system (or harmonic system) is a RFID-system for electronic article surveillance (EAS) and in Europe usually works in the ISM-bands around 900 MHz and 2.45 GHz, infrequently around 5.8 GHz. As with all EAS systems, a tag is attached to the good which is detected by detectors in the exit area of a shop (see main category Electronic Article Surveillance).
The passive transponder (tag) placed at the good receives the electromagnetic field of the detectors at the exit of the shop and use the energy to send a seperate signal out. This signal is a harmonic, so a multiple of the frequency of the detector's field. The detection of the harmonic by the detector raises an alarm. A deactivator at the checkout counter magnetizes the tag and inhibits the emission of the harmonic, so that the good with the tag can be carried outside the shop without an alarm.
These microwave systems are not that common anymore, because they can be shielded relatively easy (eg. by a metal foil).

Frequency ranges:

• 915 MHz
• 2.4–2.5 GHz
• 5.18–5.83 GHz

Type of field:

electromagnetic

Measurements (acc. to literature)

References

1. Harris C et al. (2000): Electromagnetic field strength levels surrounding electronic article surveillance (EAS) systems