![]() ![]() ![]() The team worked each chip into an RFID tag with a standard radio-frequency antenna. They purchased off-the-shelf integrated chips that are designed to switch between two different power modes: an RF energy-based mode, similar to fully passive RFIDs and a local energy-assisted mode, such as from an external battery or capacitor, similar to semipassive RFID tags. Sarma’s group took a new approach: Instead of manipulating a tag’s antenna, they tried tailoring its memory chip. So it makes antenna-based sensing a little less reliable.” “With antenna-based sensors, there’s more chance you’ll get false positives or negatives, meaning a sensor will tell you it sensed something even if it didn’t, because it’s affected by the interference of the radio fields. “Depending on the environment, radio waves are reflecting off walls and objects before they reflect off the tag, which interferes and creates noise,” Kantareddy says. The team also fabricated an antenna to sense signs of anemia in blood flowing across an RFID tag.īut Kantareddy says there are drawbacks to such antenna-centric designs, the main one being “multipath interference,” a confounding effect in which radio waves, even from a single source such as an RFID reader or antenna, can reflect off multiple surfaces. As a result, an antenna should reflect radio waves back to a reader at a characteristically different frequency or signal-strength, indicating that a certain stimuli has been detected.įor instance, Sarma’s group previously designed an RFID tag-antenna that changes the way it transmits radio waves in response to moisture content in the soil. ![]() These efforts have typically focused on manipulating a tag’s antenna, engineering it in such a way that its electrical properties change in response to certain stimuli in the environment. Recently, researchers have been experimenting with ways to turn passive RFID tags into sensors that can operate over long stretches of time without the need for batteries or replacements. Passive RFID tags are designed to harvest energy from the reader itself, which naturally emits just enough radio waves within FCC limits to power the tag’s memory chip and receive a reflected signal. Battery-assisted tags include a small battery that powers this chip. Both types of tags contain a small antenna which communicates with a remote reader by backscattering the RF signal, sending it a simple code or set of data that is stored in the tag’s small integrated chip. “When generic RFID chips can be deployed to sense the real world through tricks in the tag, true pervasive sensing can become reality.”Ĭurrently, RFID tags are available in a number of configurations, including battery-assisted and “passive” varieties. “RFID is the cheapest, lowest-power RF communication protocol out there,” Sarma says. The researchers presented their design at the IEEE International Conference on RFID, and their results appear online this week. Kantareddy developed the sensor with Rahul Bhattacharya, a research scientist in the group, and Sanjay Sarma, the Fred Fort Flowers and Daniel Fort Flowers Professor of Mechanical Engineering and vice president of open learning at MIT. You could deploy these cheaply, over a huge network.” “Imagine creating thousands of these inexpensive RFID tag sensors which you can just slap onto the walls of an infrastructure or the surrounding objects to detect common gases like carbon monoxide or ammonia, without needing an additional battery. “People are looking toward more applications like sensing to get more value out of the existing RFID infrastructure,” says Sai Nithin Reddy Kantareddy, a graduate student in MIT’s Department of Mechanical Engineering. In the future, the team plans to tailor the tag to sense chemicals and gases in the environment, such as carbon monoxide. They have developed a new ultra-high-frequency, or UHF, RFID tag-sensor configuration that senses spikes in glucose and wirelessly transmits this information. Now engineers in this group are flipping the technology toward a new function: sensing. The Auto-ID Lab at MIT has long been at the forefront of developing RFID technology. In addition to keeping tabs on products throughout a supply chain, RFID tags are used to trace everything from casino chips and cattle to amusement park visitors and marathon runners. When slapped on a milk carton or jacket collar, RFID tags act as smart signatures, transmitting information to a radio-frequency reader about the identity, state, or location of a given product. Often, these tags come in the form of paper-based labels outfitted with a simple antenna and memory chip. These days, many retailers and manufacturers are tracking their products using RFID, or radio-frequency identification tags. ![]()
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