Investigation of the impact of magnetic permeability and loss of magnetic composite materials on RFID miniaturization for conformal medical applications

The successful implementation of a flexible magnetic composite material has enabled the investigation of the potential impact on RFID (radio frequency identification) and RF passives miniaturization, considering both material-fabrication properties and geometric design parameters. The benchmarking structure is a short-circuited quarter-wavelength rectangular patch antenna for RFID UHF band (400–930 MHz). The antenna is electromagnetically modeled in HFSS full wave EM (electromagnetic) software and optimized using statistical tools, and it is found that the permeability of a practical magnetic composite can enable miniaturization by a factor larger than 3, something that could be replicated for other large-size RF passives, such as integrated inductors. The impact of the magnetic loss of the composite on the miniaturized antenna performance is also evaluated and the material is reformulated to meet the loss requirements. Then a real RFID tag is implemented for 480 MHz frequency band and good performance of the miniaturized antenna is proven both in planar and conformal configurations. Copyright © 2008 John Wiley & Sons, Ltd.