Case Studies: Reducing RFID Label Design Time - eXtras

Kamen, Germany-based Sentronik GmbH has reduced the time required to develop radio frequency identification (RFID) labels from 7 to 10 days to 2 to 3 days by simulating the labels with Flomerics’ (Marlborough, MA) MicroStripes electromagnetic simulation software. Sentronik also has been able to improve the read rate on labels to between 99 and 100% by optimizing their design in the simulation domain. “Simulation greatly improves the design process by enabling our engineers to evaluate the performance of many possible designs without having to build physical prototypes,” says Georg Siegel, chief executive officer of Sentronik.

Sentronik supplies RFID labels for a wide range of applications in the manufacturing, distribution and retail industries. The company specializes in building custom labels that provide high read rates in tough applications where conventional labels fail. Design of RFID labels is challenging because of the difficulty of sorting out the many factors that can affect performance, such as the material to which the tags are attached, the orientation of the tags, power constraints and operating frequency variations.

These problems are difficult to address using traditional experimental methods because the large number of design parameters that impact read performance means that only a small area of the design space can be explored using physical experiments. In the past, Sentronik engineers relied upon calculations with spreadsheets and math calculation programs. These calculations were only rough approximations because they did not take the geometry of the labels and environment into account.

“MicroStripes has substantially improved our design process by providing an environment that enables us to define the geometry of a new design and predict its performance,” Siegel says. “We originally selected MicroStripes software because it is easier to use than other electromagnetic simulation software that we looked at. We also modeled several of our existing designs in the software and checked the results against physical tests and saw that they provided a very good match.”

Sentronik engineers usually begin the simulation process by importing a DWG file containing the geometry of the initial concept design into MicroStripes. They assign material properties to the different components of the label. They typically begin by exciting the label in free space with a wire feed and calculate the return and radiation pattern of the antenna. Engineers often evaluate many different designs until they are happy with the performance. The next step is simulating the performance of the label in a more realistic environment. Then they re-tune the antenna to resonate at the desired frequency in its installed environment.

“MicroStripes makes it possible to validate and optimize the performance of our designs before we even build the first prototype,” Siegel says. “This saves time and avoids wasting money building prototypes that don’t work. We can predict the return loss and radiation pattern of RFID tags under a wide range of real-world operating conditions in order to ensure high read rates. Electromagnetic simulation gives us a significant competitive advantage by helping us to design labels that provide better performance than those of our competitors.”