Gentag Bringing Active Abilities to Passive RFID Tags

Gentag is touting a way to add classic active-tag capabilities-including temperature sensors-to lower-cost passive RFID tags for not even a penny more than an ordinary passive tag.

A Washington-based IP development company is talking up a patented method it says will allow low-cost passive RFID tags to monitor temperatures just as active tags do, but for less than one-twentieth the cost.

A statement from Gentag describes the patented offering as "an ultra-linear, low-power, single-calibration temperature-sensor circuit that can be directly integrated on any chip for either the Gen 2 UHF or the 13.56MHz global RFID markets."

Gentag argues that because it directly integrates with the RFID chip, it can deliver a low direct cost and, because the sensor claims to need only a single temperature calibration point at the moment of chip testing, it can also deliver cost savings during manufacturing.

The temperature control claims make this announcement, if nothing else, intriguing as that has been the centerpiece for many of RFIDs most alluring—and challenging—potential capabilities.

"Gentags temperature sensor is analog in nature and is specifically designed to consume minute amounts of power when it is on and reading out tag temperature—and none when off: It is always in thermal equilibrium with the tag. It can be switched on and off very quickly and can be fabricated using generic digital CMOS technology," the companys statement said.

"Accuracy depends on the calibration temperature; when calibrated at 40 C, the sensors measured accuracy is ±1 C over the industrial temperature range (-20 to +100 C), and ±0.1 C over the medical temperature range (34 to 42 C)," the statement said.

Traditional active RFID chips need their own power supplies to both boost signal distance as well as to power their sensors, said Marc Cohen, Gentags vice president for engineering and microelectronics. While passive tags today sell for between 5 and 7 cents, active tags can sell for $15 to $20.

/zimages/4/28571.gifReaders and tags make a splash at a recent RFID show. Click here to read more.

Cohen said his companys sensor can be integrated with a passive chip, and the cost will be "less than a cent," although he expects them to be sold for about $1.

The Gentag-equipped tag "shifts all of the power—both literally and figuratively—to the reader," which, Cohen said, "makes the tags very dumb and very cheap."

Gentag then takes a small leap, suggesting that the temperature controls can help the chip in multiple other ways.

"This unique (temperature monitoring) circuit establishes a reference for many other possible analog RFID sensors. Most sensors are themselves temperature dependent. Therefore, it becomes essential that an independent measure of temperature be made for accurate RFID sensor calibration and robust measurements of variables such as pressure, humidity, and conductivity," the statement said.

"In addition, the same temperature sensor circuit can be utilized to establish accurate voltage or current references that are independent of temperature, references which facilitate the integration of many different kinds of sensors on passive, BAP, or active RFID sensor tags."

Retail Center Editor Evan Schuman can be reached at

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