volume | PIER Journals

Abstract

Accurate approximations of the conductance and the conductance bandwidth of an electrically small antenna valid in resonant and antiresonant ranges were found. It is shown that the conductance bandwidth of an efficient antenna tuned on maximal power of radiation is inversely proportional to the magnitude of the frequency derivative of the input impedance |Z'(ω_cd)| of the antenna at frequency of maximal conductance. That is a generalization of the well known relationship according to which, the conductance bandwidth of an antenna tuned on resonance in resonant ranges is inversely proportional to the magnitude of the frequency derivative of the input reactance of the antenna |X'₀(ω₀)| at resonant frequency. Obtained approximate formulas display inverse proportionality of the conductance bandwidth to the approximate quality factor of the antenna throughout resonant and antiresonant ranges. A differential definition of the fractional conductance bandwidth was formulated, which is convenient for the case of closely spaced resonances of an antenna. As an example, numerical calculations for oblate spheroidal and spherical antennas in shells with negative permittivity in resonant and antiresonant ranges was used to confirm accuracy of the obtained approximations of the conductance and the conductance bandwidth of an electrically small antenna.

1. Yaghjian, A. D. and S. R. Best, "Impedance, bandwidth and Q of antennas," IEEE Trans. Antennas Propag., Vol. 53, No. 4, 1298-1324, Apr., 2005.
doi:10.1109/TAP.2005.844443 Google Scholar

2. Fante, R. L., "Quality factor of general ideal antennas," IEEE Trans. Antennas Propag., Vol. 17, No. 2, 151-155, Mar., 1969.
doi:10.1109/TAP.1969.1139411 Google Scholar

3. Rhodes, D. R., "On the quality factor of strip and line source antennas and its relationship to super directivity ratio," IEEE Trans. Antennas Propag., Vol. 20, No. 3, 318-325, May, 1972.
doi:10.1109/TAP.1972.1140191 Google Scholar

4. McLean, J. S., "A re-examination of the fundamental limits on the radiation Q of electrically small antennas," IEEE Trans. Antennas Propag., Vol. 44, No. 5, 672-676, May, 1996.
doi:10.1109/8.496253 Google Scholar

5. Collin, R. E. and S. Rothschild, "Evaluation of antenna Q," IEEE Trans. Antennas Propag., Vol. 17, No. 1, 23-27, Jan., 1964.
doi:10.1109/TAP.1964.1138151 Google Scholar

6. Gustafsson, M. and S. Nordebo, "Bandwidth, Q factor, and resonance models of antennas," Progress In Electromagnetics Research, Vol. 62, 1-20, 2006.
doi:10.2528/PIER06033003 Google Scholar

7. Vassiliadis, A. and R. L. Tanner, "Evaluating the impedance broadbanding of antennas," IEEE Trans. Antennas Propag., Vol. 6, No. 3, 226-231, Jul., 1958. Google Scholar

8. Stuart, H. R., S. R. Best, and A. D. Yaghjian, "Limitations in relating quality factor to bandwidth in a double resonance small antenna," IEEE Antennas and Wireless Propag. Lett., Vol. 6, No. 6, 460-463, 2007.
doi:10.1109/LAWP.2007.905018 Google Scholar

9. Vorobyev, O. B., "Efficient electrically small oblate spheroidal and spherical antennas in shells with negative permittivity," Progress In Electromagnetics Research B, Vol. 21, 151-170, 2010. Google Scholar

10. Stuart, H. R. and A. Pidwerbetsky, "Electrically small antenna elements using negative permittivity resonators," IEEE Trans. Antennas Propag., Vol. 54, No. 6, 1644-1653, Jun., 2006.
doi:10.1109/TAP.2006.875498 Google Scholar

11. Stén, J. C.-E., "Radiation Q of a small antenna enclosed in an oblate spheroidal volume: Transverse-to-axis polarisation," AEÜ --- Int. J. Electron. Commun., Vol. 57, No. 3, 201-205, 2003.
doi:10.1078/1434-8411-54100162 Google Scholar

12. Wang, Y., J. Z. Li, and L. X. Ran, "An equivalent circuit modeling method for ultra wide-band antennas," Progress In Electromagnetics Research, Vol. 82, 433-445, 2008.
doi:10.2528/PIER08032303 Google Scholar

13. Ziolkowski, R. W. and A. Erentok, "Metamaterial-based efficient electrically small antennas," IEEE Trans. Antennas Propag., Vol. 54, No. 7, 2113-2130, Jul., 2006.
doi:10.1109/TAP.2006.877179 Google Scholar

14. Adams, J. J. and J. T. Bernhard, "Tuning method for a new electrically small antenna with low Q," IEEE Antennas Wireless Propag. Lett., Vol. 8, 303-306, 2009.
doi:10.1109/LAWP.2009.2015437 Google Scholar

15. Best, S. R., "Low Q electrically small linear and elliptical polarized spherical dipole antennas," IEEE Trans. Antennas Propag., Vol. 53, 1047-1053, 2005.
doi:10.1109/TAP.2004.842600 Google Scholar

16. Best, S. R., "A comparison of electrically small spherical helix and spherical resonator antennas," The Second European Conference on Antennas and Propagation, EuCAP, 1-6, Nov. 11--16, 2007. Google Scholar

Dr. Oleg B. Vorobyev