In an Academic Study, RFID Fractal Antenna Wins Out

By Laurie Sullivan

May 23, 2007—In a recent study carried out by researchers at the Tampere University of Technology's Rauma Research Unit, in Finland, a fractal UHF RFID handheld reader antenna performed better than traditional antenna designs. The research findings were published in a paper entitled "Read Range Performance Comparison of Compact Reader Antennas for a Handheld UHF RFID Reader," in the April 2007 edition of the online magazine IEEE Applications & Practices.

The independent research compared the read range and orientation sensitivity of five miniature antennas, used in conjunction with a handheld UHF RFID reader. Created by the research team, the antennas consisted of four linearly polarized designs—a rectangular patch, an H-shaped patch, a fractal patch and a balanced dipole—as well as one circularly polarized design. The results showed that the fractal antenna had the longest read range (see the table on the following page).

Results of the research showed the fractal antenna to have the longest read range.

The researchers suggest that the existence of small, lightweight UHF RFID interrogators with an extended battery life and long read range might increase interest in supply chain RFID applications that track inventory through manufacturing facilities, warehouses and retail stores. Fractal antennas could provide the handheld readers the required performance.

Conducted in 2006 and led by Leena Ukkonen, one of the paper's coauthors and a professor at Tampere University of Technology, the study relied on tests done with the PL 3000, a UHF RFID handheld interrogator manufactured by Nordic ID, based in Salo, Finland.

The reader antennas were attached to the handheld reader externally, to take into account the effects of the electronic components inside the reader unit. To carry out the test, the researchers taped each antenna to the casing of the handheld reader, then measured the maximum reliable read range (MRRR) of four different commercial tags affixed to an empty corrugated cardboard box. MRRR was defined as the distance at which the tag could be continuously identified for at least one minute, with the tag and reader antenna aligned with one another.