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IEEE Transactions on Antennas and Propagation
Volume 46 Number 6, June 1998

Dipole Configurations with Strongly Improved Radiation Efficiency for Hand-Held Transceivers

Page 798.

Abstract:

In this paper the design criteria for antenna structures with improved radiation efficiency while operating in close vicinity to a biological scatterer were investigated. The study was performed using a simple \lambda/2 dipole combined with a directive or reflective element. The optimization criteria were the effective radiation efficiency, the spatial peak specific absorption rate (SAR), and the sensitivity of the input resistance to the distance from the scatterer. It could be demonstrated that the primary design criterion to improve the radiation efficiency is not directivity but the reduction of the maximum incident magnetic field strength in the exposed skin area of the user's head. For the reflectively coupled dipole, all performance parameters could be improved by several decibels compared to a standard \lambda/2 dipole, whereas for some other directive structures, the performance was impaired. The study was conducted with the generalized multipole technique (GMT) numerical simulation method, the results of which were validated by measurement methods.

References

1. N. Kuster and Q. Balzano, "Energy absorption mechanism by biological bodies in the near field of dipole antennas above 300 MHz," IEEE Trans. Veh. Technol., vol. 41, pp. 17-23, Feb. 1992.
2. V. Hombach, K. Meier, M. Burkhardt, E. Kühn, and N. Kuster, "The dependence of EM energy absorption upon human head modeling at 900 MHz," Trans. Microwave Theory Tech., vol. 44, pp. 1865-1873, Oct. 1996.
3. K. Meier, R. Ka¯stle, V. Hombach, R. Tay, and N. Kuster, "The dependence of EM energy absorption upon human head modeling at 1800 MHz," IEEE Trans. Microwave Theory Tech., vol. 45, pp. 2058-2062, Oct. 1997.
4. R. Y.-S. Tay, "Contributions towards the optimization of hand-held mobile telecommunication equipment by computational electromagnetics," Ph.D. dissertation, Swiss Fed. Inst. Technol., Zurich, Switzerland, 1997.
5. N. Kuster, Q. Balzano, and J. Lin, Eds., Mobile Communications Safety.London, U.K.: Chapman Hall, 1997, p. 273.
6. L. Slesin, Ed., "Swiss Tests Show Wide Variation in Radiation Exposure from Cell Phones," Microwave News, vol. 17, no. 6, pp. 1-11, Dec. 1997.
7. G. F. Pedersen and J. B. Andersen, "Integrated antennas for hand-held telephones with low absorption," in Proc. 44th IEEE Veh. Technol. Conf., Stockholm, Sweden, June 1994, pp. 1537-1541.
8. K. Noguchi, M. Ando, N.-h. Goto, M.-N. Hirose, T. Uno, and Y.-T. Kamimura, "Directional antennas for portable telephones," IEICE Trans. Commun., vol. E79-B, no. 9, pp. 1234-1241, Sept. 1996.
9. F. Schönborn, M. Burkhardt, and N. Kuster, "Differences in energy absorption between heads of adults and children in the near field of sources," Health Phys., vol. 74, no. 2, pp. 160-168, Feb., 1997.
10. R. Y.-S. Tay and N. Kuster, "Performance of the generalized multipole technique (GMT/MMP) in antenna design and optimization," Appl. Computat. Electromagn. Soc. (ACES) J., vol. 9, no. 3, pp. 79-89, 1994.
11. N. Kuster, "Multiple multipole method for simulating EM problems involving biological bodies," IEEE Trans. Biomed. Eng., vol. 40, pp. 611-620, July 1993.
12. C. Hafner and L. H. Bomholt, The 3-D Electrodynamic Wave Simulator.New York: Wiley, 1993.
13. Q. Balzano, O. Garay, and F. R. Steel, "Heating of biological tissue in the induction field of VHF portable radio transmitters," IEEE Trans. Veh. Technol., vol. VT-27, pp. 51-56, May 1978.
14. G. Hartgrove, A. Kraszewski, and A. Surowiec, "Simulated biological materials for electromagnetic radiation absorption studies," Bioelectromagn., vol. 8, no. 1, pp. 29-36, 1987.
15. T. Schmid, O. Egger, and N. Kuster, "Automated E-field scanning system for dosimetric assessments," IEEE Trans. Microwave Theory Tech., vol. 44, pp. 105-113, Jan. 1996.
16. N. Kuster, R. Ka¯stle, and T. Schmid, "Dosimetric evaluation of handheld mobile communications equipment with known precision," IEICE Trans. Commun., vol. E80-B, no. 5, pp. 645-652, May 1997.