Theme
Radiation Protection & Safety
INSTITUTION
Imam Abdulrahman bin Faisal University
Radio-frequency identification (RFID) is a wireless communication system based on the transmission of radio frequency signals through antennas between a tag and a reader. This system mainly consists of three parts: tag, reader, and middleware. Tag is attached to objects needed identification. Reader is the connection bridge between the tag and the computer. RFID system controlled by a workstation with computer. Antenna represents the main part of the tag. The antenna “that part of a transmitting or receiving system that is designed to radiate or to receive electromagnetic waves.”
Specific Absorption Rate (SAR) is the amount of energy absorbs by one-unit mass of body’s tissue. SAR is measuring the amount of increase in body temperature by one degree Celsius. SAR value represents the medical safety constraint based on engineering standards. According to Federal Communications Commission (FCC), it measured in watts per kilogram (W/kg) with maximum value 1.6 W/kg for 1 g of tissue. While European Union (EU) specify the limits to be within 2 W/kg for 10 g of tissue.
The main results were:
- Reflection coefficient: the ratio between the transmitted power and reflected power à shows that the antenna operates at 900 MHz with -14.070713 dB.
Antenna Geomety -front and back view Reflection coefficient (S11)
- SAR: At the centre of the phantom, the absorbed power is maximum and decreases as go far from the centre. The maximum power absorbed was 0.989 W/kg, which is less than 1.6 W/kg. So according to FCC the design is safe to use.
SAR value in CST software
- Electric and magnetic fiels: The results demonstrate that the maximum value in the magnetic field meets the minimum value in the electric field, and the minimum value in the magnetic field meets the maximum value in the electric field.
Electric filed (V/m) in 1D plane. Magnetic field (A/m) in a 1D plane.
1- The tag’s antenna designed using CST; to have optimal geometrical dimensions that fits for the targeted application. The proposed geometry, Modified Dipole Antenna, designed to operate on 900 MHz.
2- The proposed antenna was tested in term of performance parameters: resonant frequency, gain, bandwidth, and reflection coefficient (S11).
3- Homogenous phantom, mimics the chest muscle, designed and added to the proposed antenna. SAR calculated and compared to standard value of Federal Communications Commission (FCC)
4- The SAR is an important parameter to measure since it reflects the safety level of the design to the patient. SAR calculated as following:
Where
σ = electrical conductivity, measured in (S/m).
E = electric field, measured in (v/m).
ρ = sample density, measured in (kg/m3).
This project shows the potential of utilizing RFID technology in transferring medical information, specially bio-signal. The focus was to design antenna operates in 900 MHz and suitable to use and interact with the human body safely. The results show that the proposed antenna matches the size limitation since it has small geometry and the SAR value was in the safe limit.
In this work a homogenous phantom was used to mimic the chest tissues. To get a more accurate result for SAR heterogeneous phantom is better to use.
[1] V. D. Hunt, A.Puglia, and M. Puglia, RFID: a guide to radio frequency identification. John Wiley & Sons, 2007.
[2] J. Landt, "The history of RFID," IEEE Potentials, vol. 24, no. 4, pp. 8-11, 2005.
[3] L. Yang, A. Rida, and M. M. Tentzeris, "Design and development of radio frequency identification (RFID) and RFID enabled sensors on flexible low cost substrates," Synthesis Lectures on RF/Microwaves, vol.1, no. 1, pp. 1-89, 2009.
[4] S. A. Weis, "RFID (radio frequency identification): Principles and applications," System, vol. 2, no. 3, pp. 1-23, 2007.
[5] K. Kamarulazizi and D. W. Ismail, "Electronic toll collection system using passive RFID technology," Journal of Theoretical and Applied Information Technology, vol. 2, 2010.
[6] P. J. Soh, G. Vandenbosch, F. H. Wee, A. van den Bosch, M. Martinez-Vazquez, and D. Schreurs, "Specific Absorption Rate (SAR) Evaluation of Textile Antennas," IEEE Antennas and Propagation Magazine, vol. 57, no. 2, pp. 229-240, 2015.