A PCB-integrated multi-slotted PIFA for 2.5 GHz autonomous RFID or Bluetooth applications

Abstract

We present a compact planar antenna integrated on printed circuit board (PCB) for power-harvesting RFID tags operating at 2.5 GHz or Bluetooth dongles. The antenna, printed on FR4, is a Planar Inverted-F Antenna (PIFA)-type design with a set of optimized slots and provides high radiation efficiency and appropriate bandwidth, while presenting a low profile and very small area. Unlike expensive ceramic antennas, the present implementation is integrated directly on the system’s PCB and provides an inexpensive approach of equal or better performance to expensive ceramic antennas. The small size is due to the optimized multiple slots and the scaling with the permittivity of the FR4. A special design separating the PIFA into two stacked dielectric layers by-passes the traditionally suppressed efficiencies, which was the main obstacle for integrating PIFAs on PCBs, and restores much higher efficiencies. Hence, it creates a practical implementation of a very small antenna completely integrated on the system’s PCB appropriate for 2.5 GHz power-harvester or Bluetooth tags. We validate the design with a prototype embedded within the PCB of an autonomous RFID tag by measuring its return loss, efficiency, and radiation patterns at the operation frequency band.