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4 - Fundamental limitations of small antennas

Published online by Cambridge University Press:  05 January 2014

Kyohei Fujimoto  and
Hisashi Morishita
Kyohei Fujimoto
Affiliation:
University of Tsukuba, Japan
Hisashi Morishita
Affiliation:
National Defense Academy, Japan
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Summary

Fundamental limitations

It is commonly understood that as antennas reduce in size, antenna gain and efficiency will degrade and the bandwidth tends to be narrower. Then, a question arises how small a dimension an antenna can take for practical use? Or, what will happen when the antenna dimension is limitlessly reduced? One answer was given by J. D. Kraus, who showed that a small antenna could have effective aperture of as high as 98 percent of that of a half-wave dipole antenna, if the antenna could be perfectly matched to the load [1]. It suggests that however small an antenna is, the antenna can intercept almost the same power (only 8 percent less) as a half-wavelength dipole does. In other words, there seems to be no limitation in reducing the antenna size so long as the antenna could be perfectly matched. Unfortunately, the perfect matching is impossible when an antenna becomes extremely small, because the smaller the antenna size tends to be, the harder the antenna matching will become, as was mentioned before. In addition, losses existing in the antenna structure and the matching circuit will exceed the radiation resistance, resulting in significant reduction of the effective aperture that corresponds to reduction of the radiation power and the degradation of the radiation efficiency. Regarding the antenna impedance, increase in reactive component and decrease in the resistive component results in high Q, and as a consequence bandwidth will be narrowed. Thus, the size reduction of an antenna also affects Q and the bandwidth as well. Then it is rather natural to say that there is a fundamental limitation applying to the size reduction of antenna dimensions.

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Modern Small Antennas , pp. 23 - 38
Publisher: Cambridge University Press
Print publication year: 2014

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References

Kraus, J. D., Antennas, 3rd edn., McGraw-Hill, 2002, pp. 30–33.Google Scholar
Wheeler, H. A., Fundamental Limitations of Small Antennas, Proceedings of IRE, vol. 35, Dec 1947, pp. 1479–1484.CrossRefGoogle Scholar
Wheeler, H. A., Small Antennas, in Jasik, H. (ed.), Antenna Engineering Handbook, 2nd edn., McGraw-Hill, 1984, chapter 6.Google Scholar
Wheeler, H. A., The Radian Sphere Around a Small Antenna, Proceedings of IRE, vol. 47, August 1959, pp. 1325–1331.CrossRefGoogle Scholar
Wheeler, H. A., Antenna Topics in My Experiences, IEEE Transactions on Antennas and Propagation, vol. 33, 1985, no. 2, pp. 144–151.CrossRefGoogle Scholar
Wheeler, H. A., A Helical Antenna for Circular Polarization, Proceedings of IRE, vol. 35, 1947, pp. 1484–1488.CrossRefGoogle Scholar
Kraus, J. D. and Marhefka, R. J., Antennas, 3rd edn., 2002, McGraw-Hill, pp. 292–293.Google Scholar
Wheeler, H. A., The Spherical Coil as an Inductor, Shield, and Antenna, Proceedings of IRE, vol. 46, 1958, pp. 1595–1602.CrossRefGoogle Scholar
pp. 147–148 in.
p. 148 in [5] and Wheeler, H. A., Small Antennas, IEEE Transactions on Antennas and Propagation, vol. 23, 1975, pp. 462–469.CrossRefGoogle Scholar
pp. 146–147 in.
Wheeler, H. A., Fundamental Limitations of a Small VLF Antenna for Submarines, IEEE Transactions on Antennas and Propagation, vol. 6, 1958, pp. 123–125.CrossRefGoogle Scholar
Chu, L. J., Physical Limitations of Omni Directional Antennas, Research Laboratory of MIT, MIT Tech Report no. 64, 1948.Google Scholar
King, R. W. P., Linear Antennas, Harvard University Press, 1956.CrossRefGoogle Scholar
King, R. W. P., and Harrison, C. W., Antennas and Waves, The MIT Press, 1969.Google Scholar
pp. 171–182 in.
Collin, R. E. and Rothschild, S., Evaluation of Antenna Q, IEEE Transactions on Antennas and Propagation, vol. 12, 1964, pp. 23–27.CrossRefGoogle Scholar
Hansen, R. C., Fundamental Limitations in Antennas, Proceedings of IEEE, vol. 69, 1981, no. 2, pp. 170–181.CrossRefGoogle Scholar
McLean, J. S., A Re-Examination of the Fundamental Limits on the Radiation Q of Electrically Small Antennas, IEEE Transactions on Antennas and Propagation, vol. 44, 1996, pp. 672–676.CrossRefGoogle Scholar
Folts, H. D. and McLean, J. S., Limits on the Radiation Q of Electrically Small Antennas Re-Estimated to Oblong Bounding Regions, IEEE Antennas and Propagation Society International Symposium, July 1999, vol. 4, pp. 2702–2705.Google Scholar
Thiele, G. A., Detweiler, P. L., and Peno, R. P., On the Lower Bound of the Radiation Q for Electrically Small Antennas, IEEE Transactions on Antennas and Propagation, vol. 51, 2003, pp. 1263–1269.CrossRefGoogle Scholar
Geyi, W., Physical Limitations of Antenna, IEEE Transactions on Antennas and Propagation, vol. 51, 2003, pp. 2116–2123.CrossRefGoogle Scholar
Geyi, W., A Method for the Evaluation of Small Antenna Q, IEEE Transactions on Antennas and Propagation, vol. 51, 2003, pp. 2124–2129.CrossRefGoogle Scholar
Geyi, W., Jarmauszewski, P., and Qi, Y, The Foster Reactance Theorem for Antennas and Radiation Q, IEEE Transactions on Antennas and Propagation, vol. 48, 2000, pp. 401–408.CrossRefGoogle Scholar
Best, S. R., Low Q Electrically Small Linear and Elliptical Polarized Spherical Dipole Antennas, IEEE Transactions on Antennas and Propagation, vol. 53, 2005, no. 3, pp. 1047–1053.CrossRefGoogle Scholar
Yaghjian, A. D. and Best, S, Impedance, Bandwidth, and Q of Antennas, IEEE Transactions on Antennas and Propagation, vol. 53, 2005, no. 4, pp. 1298–1324.CrossRefGoogle Scholar
Best, S. R., Bandwidth and the Lower Bound on Q for Small Wideband Antennas, IEEE APS International Symposium, 2006, pp. 647–650.
Best, S. R., A Low Q Electrically Small Magnetic (TE Mode) Dipole, IEEE Antennas and Wireless Propagation Letters, vol. 8, 2009, pp. 572–575.CrossRefGoogle Scholar
Thal, H. L, Gain and Q bounds for coupled TM--TE modes, IEEE Transactions on Antennas and Propagation, vol. 57, 2009, no. 7, pp. 1879–1885.CrossRefGoogle Scholar
Thal, H. L., New Radiation Q Limits for Spherical Wire Antennas, IEEE Transactions on Antennas and Propagation, vol. 54, 2006, no. 10, pp. 2757–2763.CrossRefGoogle Scholar
Hansen, R. C. and Collin, R. E., A New Chu Formula for Q, IEEE Antennas and Propagation Magazine, vol. 51, 2009, no. 5. pp. 38–41.CrossRefGoogle Scholar
Gustafsson, M., Sohl, C., and Kristenssen, G., Illustrations of New Physical Bounds on Linearly Polarized Antennas, IEEE Transactions on Antennas and Propagation, vol. 57, 2009, no. 5, pp. 1319–1326.CrossRefGoogle Scholar
Vandenbosch, G. A. E., Reactive Energies, Impedance, and Q Factor of Radiating Structures, IEEE Transactions on Antennas and Propagation, vol. 58, 2010, no. 4, pp. 1112–1127.CrossRefGoogle Scholar
Kim, O. S., Breinbjerg, O., and Yaghjian, A. D., Electrically Small Magnetic Dipole Antennas With Quality Factors Approaching the Chu Lower Bound, IEEE Transactions on Antennas and Propagation, vol. 58, 2010, no. 6, pp. 1898–1905.CrossRefGoogle Scholar
Yaghjian, A. D. and Stuart, H R., Lower Bounds on the Q of Electrically Small Dipole Antennas, IEEE Transactions on Antennas and Propagation, vol. 58, 2010, no. 10, pp. 3114–3121.CrossRefGoogle Scholar
Stuart, H. R. and Yaghjian, A. D., Approaching the Lower Bounds on Q for Electrically Small Electric-Dipole Antennas Using High Permeability Shells, IEEE Transactions on Antennas and Propagation, vol. 58, 2010, no. 12, pp. 3865–3872.CrossRefGoogle Scholar
Kim, O. S. and Breinbjerg, O., Lower Bound for the Radiation Q of Electrically Small Magnetic Dipole Antennas With Solid Magneto-dielectric Core, IEEE Transactions on Antennas and Propagation, vol. 59, 2011, no. 2, pp. 679–681.CrossRefGoogle Scholar

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