volume | PIER Journals

Abstract

In time-modulated antenna arrays (TMAAs), as a result of periodical switch-on and switch-off of the antenna elements, including operating frequency (termed as center frequency) signal, sideband signals are appeared at either sides of the center frequency in integer multiples of the modulation frequency. In this paper, it is shown that without using phase shifters, just by suitably controlling the on-time instants (OTIs)and on-time durations (OTDs) of a timemodulated linear antenna array (TMLAA) elements, simultaneously, along with a pencil beam pattern at the operating frequency, a shaped beam pattern can be obtained at both the first positive and negative harmonics of the time-modulation frequency. The important advantage of such a technique is that realization of multi-beam pattern in conventional antenna array (CAA) system generally requires complex feed network, whereas by using simple radio frequency (RF) switching circuit in the feed network of TMLAA, by virtue of the properties of harmonic radiations, synthesis of a shaped pattern at either (positive or negative) harmonic results in generating the same pattern in its opposite harmonic, and the synthesized patterns at different harmonics can be simultaneously used as independent communication channels. By employing a differential evolution (DE) based optimization method, numerical results for a 16-element TMLAA with uniform excitation show that in conjunction with a pencil beam pattern at the center frequency, a flat-top or a cosec square pattern at first positive and negative sidebands of side-lobe levels (SLL) -20 dB can be synthesized by suppressing the higher sideband level (SBL) to below -10 dB.

1. Johnson, R. C., and H. Jasik, Antenna Applications Reference Guide, The McGraw-Hill Engineering, Guide Series, New York, 1984.

2. Lager, I. E., C. Trampuz, M. Simeoni, and L. P. Ligthart, "Interleaved array antennas for FMCW radar applications," IEEE Transaction on Antennas and Propagation, Vol. 57, No. 8, 2486-2490, 2009.
doi:10.1109/TAP.2009.2024573

3. Sudhakar, R. K., G. A. Morin, M. Q. Tang, and S. Richard, "Development of a 45 GHz multiple-beam antenna for military satellite communications," IEEE Transaction on Antennas and Propagation, Vol. 45, No. 10, 1036-1047, 1995.
doi:10.1109/8.467639

4. Barba, M., J. E. Page, J. A. Encinar, and J. R. Montejo-Garai, "A switchable multiple beam antenna for GSM-UMTS base stations in planar technology," IEEE Transaction on Antennas and Propagation, Vol. 54, No. 11, 3087-3094, 2006.
doi:10.1109/TAP.2006.883991

5. Bucci, O. M., G. Mazzarella, and G. Panariello, "Reconfigurable arrays by phase-only control," IEEE Transaction on Antennas and Propagation, Vol. 39, No. 7, 919-925, 1991.
doi:10.1109/8.86910

6. Durr, M., A. Trastoy, and F. Ares, "Multiple-pattern linear antenna arrays with single prefixed amplitude distributions: Modified Woodward-Lawson synthesis ," Electron. Lett., Vol. 36, No. 16, 1345-1346, 2000.
doi:10.1049/el:20000980

7. Oliveri, G. and A. Massa, "Fully-interleaved linear arrays with predictable sidelobes based on almost difference sets ," IET Radar Sonar Navigat., Vol. 4, No. 5, 649-661, 2010.
doi:10.1049/iet-rsn.2009.0186

8. Shanks, H. E. and R. W. Bickmore, "Four dimensional electromagnetic radiators," Canad. J. Phys., Vol. 37, No. 3, 263-275, 1959.
doi:10.1139/p59-031

9. Kummer, W. H., A. T. Villeneuve, T. S. Fong, and F. G.Terrio, "Ultra-low side-lobes from time modulated arrays," IEEE Transaction on Antennas and Propagation, Vol. 1, No. 6, 633-639, 1963.
doi:10.1109/TAP.1963.1138102

10. Zhu, Q., S. Yang, L. Zheng, and Z. Nie, "Design of a low side lobe time modulated linear array with uniform amplitude and subsectional optimized time steps," IEEE Transaction on Antennas and Propagation, Vol. 60, No. 9, 4436-4439, 2012.
doi:10.1109/TAP.2012.2207082

11. Yang, S., Y. B. Gan, and A. Qing, "Sideband suppression in time-modulated linear arrays by the di®erential evolution algorithm," IEEE Antennas Wireless Propag. Lett., Vol. 1, 173-175, 2002.
doi:10.1109/LAWP.2002.807789

12. Yang, S., Y. B. Gan, and P. K. Tan, "A new technique for power-pattern synthesis in time-modulated linear arrays," IEEE Antennas Wireless Propag. Lett., Vol. 2, 285-287, 2003.
doi:10.1109/LAWP.2003.821556

13. Mandal, S. K., G. K. Mahanti, and R. Ghatak, "A single objective approach for suppressing sideband radiations of ultra-low side lobe patterns in time-modulated antenna arrays,", Vol. 27, No. 14, 1767-1775, 2013.

14. Rocca, P., L. Poli, G. Oliveri, and A. Massa, "Adaptive nulling in time-varying scenarios through time-modulated linear arrays," IEEE Antennas Wireless Propag. Lett., Vol. 11, 101-104, 2012.
doi:10.1109/LAWP.2012.2183849

15. Bregains, J. C., J. Fondevila-Gomez, G. Franceschetti, and F. Ares, "Signal radiation and power losses of time-modulated arrays," IEEE Transaction on Antennas and Propagation, Vol. 56, No. 6, 1799-1804, 2008.
doi:10.1109/TAP.2008.923345

16. Yang, S., Y. B. Gan, and P. K. Tan, "Evaluation of directivity and gain for time-modulated linear antenna arrays," Microw. Opt. Technol. Lett., Vol. 42, No. 2, 167-171, 2004.
doi:10.1002/mop.20241

17. Fondevila, J., J. C. Bregains, F. Ares, and E. Moreno, "Application of time-modulation in the synthesis of sum and di®erence patterns by using linear arrays," Microw. Opt. Technol. Lett., Vol. 48, 829-832, 2006.
doi:10.1002/mop.21489

18. Yang, S., Y. B. Gan, A. Qing, and P. K. Tan, "Design of uniform amplitude time modulated linear array with optimized time sequences," IEEE Transaction on Antennas and Propagation, Vol. 53, No. 7, 2337-2339, 2005.
doi:10.1109/TAP.2005.850765

19. Poli, L., P. Rocca, L. Manica, and A. Massa, "Pattern synthesis in time-modulated linear arrays through pulse shifting ," IET Microw. Antennas Propag., Vol. 4, No. 9, 1157-1164, 2010.
doi:10.1049/iet-map.2009.0042

20. Rocca, P., L. Poli, G. Oliveri, and A. Massa, "Synthesis of sub-arrayed time modulated linear arrays through a multi-stage approach," IEEE Transaction on Antennas and Propagation, Vol. 59, No. 9, 3246-3254, 2011.
doi:10.1109/TAP.2011.2161535

21. Rocca, P., L. Manica, L. Poli, and A. Massa, "Synthesis of compromise sum-difference arrays through time-modulation," IET Radar, Sonar & Navigation, Vol. 3, No. 6, 630-637, 2009.
doi:10.1049/iet-rsn.2009.0058

22. Poli, L., P. Rocca, L. Manica, and A. Massa, "Handling sideband radiations in time-modulated arrays through particle swarm optimization," IEEE Transaction on Antennas and Propagation, Vol. 58, No. 4, 1408-1411, 2010.
doi:10.1109/TAP.2010.2041165

23. Poli, L., P. Rocca, L. Manica, and A. Massa, "Time modulated planar arrays --- Analysis and optimization of the sideband radiations," IET Microwaves, Antennas & Propagation, Vol. 4, No. 9, 1165-1171, 2010.
doi:10.1049/iet-map.2009.0379

24. Bekele, E. T., L. Poli, M. D'Urso, P. Rocca, and A. Massa, "Pulse-shaping strategy for time modulated arrays --- Analysis and design," IEEE Transaction on Antennas and Propagation, Vol. 61, No. 7, 3525-3537, 2013.
doi:10.1109/TAP.2013.2256096

25. Li, G., S. Yang, Y. Chen, and Z.-P. Nie, "A novel electronic beam steering technique in time modulated antenna arrays," Progress In Electromagnetics Research, Vol. 97, 391-405, 2009.

26. Tennant, A., "Experimental two-element time-modulated direction finding array," IEEE Transaction on Antennas and Propagation, Vol. 58, No. 3, 986-988, 2010.
doi:10.1109/TAP.2009.2039301

27. Gang, L., S. Yang, M. Huang, and Z. Nie, "Shaped patterns synthesis in time-modulated antenna arrays with static uniform amplitude and phase excitations," Front. Electr. Electron. Eng. China, Vol. 5, No. 2, 179-184, 2010.
doi:10.1007/s11460-010-0005-2

28. Poli, L., P. Rocca, G. Oliveri, and A. Massa, "Harmonic beam forming in time modulated linear arrays," IEEE Transaction on Antennas and Propagation, Vol. 59, No. 7, 2545-2545, 2011.
doi:10.1109/TAP.2011.2152323

29. Rocca, P., G. Oliveri, and A. Massa, "Differential evolution as applied to electromagnetics," IEEE Antennas Propag. Mag., Vol. 53, No. 1, 38-49, 2011.
doi:10.1109/MAP.2011.5773566

Dr. Sujit Kumar Mandal

Dr. Gautam Mahanti

Prof. Rowdra Ghatak