The rate of wireless data transmission is limited by the antenna bandwidth. We present an efficient technique to realize a high-rate direct binary FSK modulation by using the transient properties of high-Q antennas. We show that if the natural resonance of a narrowband resonant-type antenna is switched at a high rate, the radiating signal follows the variation of resonant frequency and provides a high-rate data-transmission regardless of the narrowband characteristics of the antenna. The bit-rate in this method is dictated by the switching speed rather than the impedance bandwidth. Since the proposed technique employs the antenna in a time-varying arrangement, carrier frequencies are not required to be simultaneously within the antenna bandwidth. When demanded, the antenna is tuned to required carrier frequency according to a sequence of digital data. Moreover, if the switching frequency is properly chosen such that the stored energy in the near-zone is not dramatically disturbed, any variation in the antenna resonance will instantaneously appear in the far-field radiation due to the previously accumulated energy in the near field. Therefore, depending on the Q factor and switching speed, radiation bandwidth of the antenna can be improved independently from the impedance bandwidth. Furthermore, we show that a single RF source is sufficient to excite both carrier frequencies and the need for a VCO is obviated. Experimental results are presented to validate the feasibility of the proposed technique.
2. Miranda, H., V. Gilja, C. A. Chestek, K. V. Shenoy, and T. H. Meng, "HermesD: A high-rate long-range wireless transmission system for simultaneous multichannel neural recording applications,", Vol. 4, No. 3, 181-191, 2010.
3. Lee, S. B., M. Yin, J. R. Manns, and M. Ghovanloo, "A wideband dual-antenna receiver for wireless recording from animals behaving in large arenas," IEEE Transactions on Biomedical Circuits and Systems, Vol. 60, No. 7, 1993-2004, 2013.
4. Chu, L. J., "Physical limitations on omni-directional antennas," Journal of Applied Physics , Vol. 19, 1163-1175, 1948.
5. Harrington, R. F., "Effect of antenna size on gain, bandwidth, and effciency," Journal of Research of the National Bureau of Standards , Vol. 64D, 1-2, 1960.
6. 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, No. 5, 672-675, 1996.
7. Salehi, M. and M. Manteghi, "Utilizing non-linear inductors for bandwidth improvement," URSI-USNC National Radio Science Meeting, 2011.
8. Salehi, M. and M. Manteghi, "Bandwidth enhancement using nonlinear inductors," 2011 IEEE Antennas and Propagation Society International Symposium (APSURSI), 1-4, 2011.
9. Manteghi, M., "An inexpensive phased array design using impedance modulation," URSI-USNC National Radio Science Meeting, 2010.
10. Manteghi, M., "Non-LTI systems, a new frontier in electromag-netics theory," 2010 IEEE Antennas and Propagation Society International Symposium (APSURSI), 1-4, 2010.
11. Manteghi, M., "Antenna miniaturization beyond the fundamental limits," URSI-USNC National Radio Science Meeting, 2009.
12. Manteghi, M., "A switch-band antenna for software-defined radio applications," IEEE Antennas and Wireless Propagation Letters, Vol. 8, 3-5, 2009.
13. Manteghi, M., "Antenna miniaturization beyond the fundamental limits using impedance modulation," 2009 IEEE Antennas and Propagation Society International Symposium, (APSURSI), 1-4, 2009.
14. Wheeler, H. A., "Fundamental limitations of small antennas," Proceedings of the IRE, Vol. 35, No. 12, 1479-1484, 1947.
15. Schaubert, D. H., "Application of Prony's method to time-domain reflecto-meter data and equivalent circuit synthesis," IEEE Transactions on Antennas and Propagation, Vol. 27, No. 2, 180-184, 1979.
16. Schelkunoff, S. A., "Representation of impedance functions in terms of resonant frequencies," Proceedings of the IRE, Vol. 32, No. 2, 83-90, 1944.
17. Kim, Y. and H. Ling, "Equivalent circuit modeling of broadband antennas using a rational function approximation," Microwave and Optical Technology Letter, Vol. 48, No. 5, 950-953, 2006.
18. Adve, R. S., T. K. Sarkar, S. M. Rao, E. K. Miller, and D. R. Pflug, "Application of the cauchy method for extrapolating/interpolating narrow-band system responses," IEEE Transactions on Microwave Theory and Techniques, Vol. 45, No. 5, 837-845, 1997.
19. Michalski, K. A. and L. W. Pearson, "Equivalent circuit synthesis for a loop antenna based on the singularity expansion method," IEEE Transactions on Antennas and Propagation, Vol. 32, No. 5, 433-441, 1984.
20. Simpson, T. L., J. C. Logan, and J. W. Rockway, "Equivalent circuits for electrically small antennas using LS-decomposition with the method of moments ," IEEE Transactions on Antennas and Propagation, Vol. 37, No. 12, 1632-1635, 1989.
21. Hamid, M. and R. Hamid, "Equivalent circuit of dipole antenna of arbitrary length," IEEE Transactions on Antennas and Propagation, Vol. 45, No. 11, 1695-1696, 1997.
22. Love, A. W., "Equivalent circuit for aperture antennas," Electronics Letters, Vol. 23, No. 13, 708-710, 1987.