In this article, fractal structure is proposed for localized near-field UHF antenna of radio frequency identification (RFID) reader. In the design, traditional Koch fractal structure is modified by converting the direction of one fractal structure of each line segment. Parameters of the fractal structure are optimized to acquire strong and uniform magnetic field distribution within an interrogation zone at designated height over the antenna. Two Koch fractal near-field antennas fed from center or side are presented. And the side-fed fractal near-field antenna is fabricated and tested to demonstrate a localized coverage area with a perimeter of two wavelengths within a reading distance of 35mm above the antenna. For distance above 35mm, a sharp decrease of reading rate is observed, which demonstrates a satisfactory near-field UHF antenna.
- Koch fractal
- radio frequency identification