It seeks to combine an embedded temperature sensor unit with passive RFID circuitry in a single-chip for commercial utilisation. The emerging technology, dubbed sensor RFIDs, is expected to supersede the traditional sensor-wired equipment, making it possible to measure environmental parameters more freely and wirelessly without physical or visual contact.

"We're moving towards pressure, humidity or chemical-sensing tools. RFID suits us fine as it can be fixed everywhere. It will usher in a new age in measurement," said Manop Thamsirianunt, managing director of Silicon Craft Technology, Thailand's first privately owned IC design company which pioneered a research into - and the development of - a Thai RFID microchip, with support from the Science and Technology Ministry.

Having started the development in the middle of last year, the company said the temperature sensor RFID could be used with various applications, especially in areas where an appropriate temperature level is essential.

The sensor RFID, featuring 0.35-micron technology, is 950 x 1.5 microns in size and packed with sensors designed to measure industrial-grade temperatures from minus 40 degrees to 120 degrees Celsius with a maximum resolution of eight bits.

"It can be useful to a food supply chain trying to find out if its products have been properly stored as RFID chips can be set to sense temperatures," said Manop.

He said warehouses, cold-storage facilities and produce distributors could have miniaturised RFID tags attached to styrofoam packaging on a tray holding the food, or in a freezing chamber, to monitor the surrounding environment.

The company is trying to transfer the design to an implantable temperature sensor for an animal healthcare application with minimal structural modification, as it has chosen a robust operating frequency, between 100 kHz and 150 kHz.

"The new chip will make it possible for anyone to easily check if their pet dogs or cats are ill. The chip can give you a pet's change in temperature," he said. The chip powers itself, making external power supplies redundant and thus making it cheaper.

"The chip was out there in the market but came without any memory. This will be for a niche, premium market," said Manop. He said RFID chips are marketed globally at US$5 (Bt195) a unit, each calling for an external power supply.

Chances are Silicon Craft will market its sensor RFID chip at $2 per piece. The fully integrated complementary metal-oxide semiconductor (CMOS) battery-less device measures temperature and performs calibration to compensate for the sensor's inherent imperfections.

An RF link, using RFID's passive backscattering technique, wirelessly transmits the data to a reading device while extracting power from the same "airwave", letting the device operate anywhere and last almost forever.

The entire microchip, including the temperature sensor, consumes less than a few microamps over a half a second, thus allowing the scanning device to capture data from a longer distance. When it comes to reading the tag's temperature, an RFID reader beams the RF field to power a chip, simultaneously sending a command to activate the microchip and wirelessly collecting the data from it.

A single operation can read both the manufacturer lot's ID and the goods' temperature any time, anywhere, to ensure that each lot has been treated and maintained at the proper temperature.

The company expects that it's chip will be emulated in future low-power smart sensors.

Manop said the next-generation microchip would perform the calibration algorithm on its own.

The calibration reader will send only the reference value to a tag, leaving it to do the rest.

suchalee@nationgroup.com

Suchalee Pongprasert

The Nation