In this paper, a modified planar balanced Vivaldi antenna with endfire characteristics near the metal surface is proposed for 6-18 GHz applications. The proposed antenna structure consists of three copper layers, among which two external layers locate on the two outsides of two dielectric substrates, and the central layer is sandwiched by these two dielectric substrates. To further enhance the end-fire radiation characteristic, a number of novel techniques are proposed, including elongation and shaping of the supporting substrate of a conventional balanced antipodal Vivaldi antenna beyond its aperture, using an I-shaped slot loaded radiation patch and cutting a triangle on the edge of three copper layers. Measured and simulated results show that the proposed antenna not only exhibits good impedance bandwidth, but also improves the end-fire performance in the operational frequency of 6-10 GHz and achieves high gain in the end-fire direction, low cross-polarization and high front-to-back (F-to-B) ratio.
2. Yngvesson, , K. S., , D. H. Schaubert, T. L. Korzeniowski, E. L. Kollberg, and T. Thungren, , "Endfire tapered slot antennas on dielectric substrates," IEEE Trans. Antennas Propag., Vol. 33, 1392-1400, , 1985.
3. Wang, , N. B., Y. C. Jiao, Y. Song, L. Zhang, and F.-S. Zhang, "A microstrip-fed logarithmically tapered slot antenna for wideband applications," Journal of Electromagnetic Waves and Applications,, Vol. 23, No. 10, 1335-1344, , 2009.
4. Wang, , N. B., , Y. Song, Y. C. Jiao, L. Zhang, and F.-S. Zhang, "Extreme wideband tapered slot antenna with impedance bandwidth in excess of 21.6:1 ," Journal of Electromagnetic Waves and Applications, , Vol. 23, No. 2--3, , 231-238, , 2009.
5. Hu, , S., , C. L. Law, and W. B. Dou, , "A tapered slot antenna with °at and high gain for ultra-wideband applications," Journal of Electromagnetic Waves and Applications,, Vol. 23, No. 5--6, , 723-728, 2009.
6. Greenberg, , M. C., , K. L. Virga, and C. L. Hammond, "Performance characteristics of the dual exponentially tapered slot antenna for wireless communications applications," IEEE Trans. Vehicular Tech., Vol. 52, No. 2, 305-312, 2003.
7. Stockbroeckx, B. and, A. V. Vorst, and , "Copolar and cross-polar radiation of Vivaldi antenna on dielectric substrate," IEEE Trans. Antennas Propag., , Vol. 48, 19-25, , 2000.
8. Atiah, , A. , N. Bowring, and , "Design of flat gain UWB tapered slot antenna for on-body concealed weapons detections," Piers Online , Vol. 7, No. 5, 491-495, , 2011.
9. Shafieha, , J. H., , J. Noorinia, and C. Ghobadi, , "Probing the feed line parameters in Vivaldi notch antenna," Progress In Electromagnetics Research B, , Vol. 1, 237-252, 2008..
10. Zhou, , B., , H. Li, X. Y. Zou, and T. J. Cui, \, "Broadband and high-gain planar Vivaldi antennas based on inhomogeneous anisotropic zero-index metamaterials," Progress In Electromagnetics Research, Vol. 120, 235-247, , 2011.
11. Langley, J. D. S., , P. S. Hall, and P. Newham, "Novel ultrawide bandwidth Vivaldi antenna with low crosspolarisation," Electron. Lett., , Vol. 29, No. 23, 2004-2005, , 1993..
12. Langley, , J. D. S., P. S. Hall, and P. Newham, , "Balanced antipodal Vivaldi antenna for wide bandwidth phased arrays," IEE Proc. Microw. Antenna Propag., , Vol. 143, No. 2, 97-102, , 1996..
13. Gazit, , E., , "Improved design of the Vivaldi antenna," IEE Proceeding,, Vol. 135, No. 2, , 89-92, , 1988..
14. Bai, , J., , S. Shi, and D. W. Prather, \, "Modified compact antipodal Vivaldi antenna for 4--50 GHz UWB application," IEEE Trans. Microw. Theory Tech., , Vol. 59, No. 4, 1051-1057, 2011.
15. Mehdipour, A., , K. Mohammadpour-Aghdam, and R. Faraji-Dana, "Complete dispersion analysis of Vivaldi antenna for ultra deband applications," Progress In Electromagnetics Research , Vol. 77, 85-96, 2007.
16. Yang, , Y., , Y. Wang, and A. E. Fathy, , "Design of compact Vivaldi antenna arrays for UWB see through wall applications," Progress In Electromagnetics Research, , Vol. 82, , 401-418, , 2008.
17. Hood, , A. Z., , T. Karacolak, and E. Topsakal, "A small antipodal Vivaldi antenna for ultrawide-band applications," IEEE Antenna, Vol. 7, 656-660, , 2008.
18. Jolani, , F., , G. R. Dadashzadeh, M. Naser-Moghadasi, and A. M. Dadgarpour, , "Design and optimization of compact bal-anced antipodal Vivaldi antenna," Progress In Electromagnetics Research C,, Vol. 9, , 183-192, , 2009.
19. Fei, , P., Y.-C. Jiao, W. Hu, and F.-S. Zhang, "A miniaturized an-tipodal Vivaldi antenna with improved radiation characteristics ," IEEE Antenna Wireless Propag. Lett.,, Vol. 10, 127-130, , 2011.
20. Bourqui, , J., M. Okoniewski, and E. C. Fear, , "Balanced antipodal Vivaldi antenna with dielectric director for near-field microwave imaging," IEEE Trans. Antennas Propag., , Vol. 58, No. 7, 2318-2326, 2010.
21. Elsherbini, , A., , et al., "UWB antipodal Vivaldi antennas with protruded dielectric rods for higher gain, symmetric patterns and minimal phase center variations," IEEE Antennas pag. Society International Symposium, , 1973-1976, , 2006..
22. Kota, , K. , L. Shafai, and , "Gain and radiation pattern enhancement of balanced antipodal Vivaldi antenna," Electron. Lett., , Vol. 47, 303-304, , 2011.
23. Adamiuk, , G., , T. Zwick, and W. Wiesbeck, "Compact, dual-polarized UWB-antenna embedded in a dielectric," IEEE Trans. Antennas Propag.,, Vol. 58, No. 2, , 279-286, , 2010..