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Ultracapacitor Offers 75-Foot Read Range for Passive Tags

Storing energy from a small solar panel enables the passive UHF S/Cap tag to perform like a battery-assisted tag.
By Mary Catherine O'Connor
Jun 29, 2011Enable IPC, a technology-development startup located in Madison, Wisc., has announced the availability of its new passive ultrahigh-frequency (UHF) RFID tag, known as the S/Cap tag, which it claims can be read from a distance of 75 feet. The tag, designed for asset-tracking applications, performs like a battery-assisted tag, but instead of a battery uses an ultracapacitor to boost the inlay's read distance.

An ultracapactitor is a very powerful capacitor—a device used to store an electric charge, which can be utilized with or without a battery. Ultracapactitors can take and release a charge faster than batteries can, as well as withstand more charges and discharges than batteries can accommodate.

The S/Cap tag

South Korean tag manufacturer RF Camp provides the EPC Gen 2-compliant UHF passive RFID inlay used in the S/Cap. RF Camp has also announced plans to resell and distribute the S/Cap tag in South Korea. EM Microelectronic supplies its EM4324 integrated circuit for the inlay. The ultracapacitor is connected on a circuit board to both the tag's chip—via a bonding pad originally designed to mount a battery to the chip for a battery-assisted passive (BAP) tag—and its antenna.

The S/Cap tag is the first in a line of RFID tags that Enable IPC plans to produce, all using ultracapacitors (also known as supercapacitors) rather than batteries to extend the tag's range.

The ultracapacitor still requires a power source to obtain the energy it stores, the company notes. The S/Cap employs a small solar panel mounted on the tag's face to power the ultracapacitor. This means it works well outdoors, says David Walker, Enable IPC's CEO. However, he says, the solar panel can still generate power from indoor light. Even if the tag is placed in darkness for many days, he adds, it will still remain readable, since it is a passive tag that receives energy from a reader—but the extended range, made possible by the solar power, will be lost.

In the presence of light, Walker explains, the S/Cap tag has a read range of 75 feet. Metallic surfaces or other conductive materials, he notes, can detune the RF antenna and reduce the range, as with an ordinary UHF tag, but the company is currently developing a metal-mount version, designed to overcome this limitation.

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