Like the other two EAS technologies swept-RF also uses a transmitter to create a surveillance area where tags and labels are detected. However, the transmitter sends a signal that sweeps frequency, a typical range being from 7.4 to 8.8 MHz.
The transmitter signal energizes the swept-RF device which usually consists of a flat circuit containing a laminar capacitor and an inductor (a printed or etched coil) both of which store electrical energy. When connected together in a loop (i.e.. In parallel), these components pass energy back and forth (resonate). The resonant frequency is chosen by matching the storage capacity of the coil and capacitor. The tag responds by emitting a signal that is detected by a receiver. Accordingly, sweeping frequency picks up each differently specified inductor - capacitor (LC) pair, one at a time.
In addition to the small tag signal, the receiver also responds to the much larger transmitter signal. By detecting a phase difference between these two signals, and certain other properties of the tag signal, the receiver recognises the presence of a tag and generates an alarm, without being confused by other electronic devices in the neighbourhood.
Swept RF EAS is supplied by Checkpoint, world number two in EAS and many other companies including Lintec and Miyake in Japan and Nedap in The Netherlands. Not all systems are compatible, Though the tag designs are very similar and there is common cause for an interoperable standard. This is of particular interest in Europe and Japan.
Swept-RF is the first or second most popular EAS technology (proponents dispute the rankings) being of reasonable range and cost, fairly tolerant of bending and of thickness that is intermediate between magnetoacoustic and electromagnetic tags. It is suitable for most packaging.
About five other companies make RFID i.e. multibit versions of Swept RF with modest commercial success.
See the IDTechEx report Printed & Chipless RFID