In this paper, a 2 x 1 duplex antenna array with small frequency space and high isolation between transmitting and receiving bands is presented. The duplex antenna array element consists of a pair of radiating patches for bidirectional radiation, a set of microstrip resonator and H-slot resonator coupled to the patches for transmitting, and the other set of microstrip and H-slot resonators coupled to the patches for receiving. The H slots are designed for the operations of coupling and the elements of the bandpass filters. The two antenna elements of the 2 x 1 array are connected by transmitting and receiving channels microstrip power-split resonators. The array achieves a compact size and high performances in terms of high isolation and small Tx-Rx frequency space. Higher than 30 dB and 40 dB ports isolation at 1.94-1.99 GHz and 2.43-2.52 GHz is realized. And the Tx-Rx frequency space Δf=(fr-ft) is smaller than 0.23 times of the central frequency (fr+ft)/2.
2. Hanseishi, M. and M. Konno, "Dual-polarized planar antenna fed by dog-bone slots," IEEE 11th Int. Antenna and Propagation Conf., 45-48, 2001.
3. Row, J. S. and Electron. Lett., "Two-element dual-frequency microstrip antenna with high isolation,", Vol. 39, No. 25, 1786-1787, 2003.
4. Chiou, T. W. and K. L. Wong, "Broad-band dual-polarized single microstrip patch antenna with high isolation and low cross polarization," IEEE Trans. Antennas Propagat., Vol. 50, 399-401, Mar. 2002.
5. Chung, Y., S. S. Jeon, S. Kim, D. Ahn, J. I. Choi, and T. Itoh, "Multifunctional microstrip transmission lines integrated with defected ground structure for RF front-end application," IEEE Trans. Microw. Theory Tech., Vol. 52, No. 5, 1425-1432, 2004.
6. Tirado-Mendez, J. A., H. Jardon-Aguilar, R. Flores-Leal, M. Reyes-Ayala, and E. Andrade- Gonzalez, "Improving performance of non-duplexer active transceiver antenna with defected structures," IET Microw. Antennas Propag., Vol. 4, No. 3, 342-352, 2010.
7. Luis, I. S., V. R. Jose-Luis, and R. I. Eva, "High isolation proximity coupled multilayer patch antenna for dual-frequency operation," IEEE Trans. Antennas Propagat., Vol. 56, No. 4, 1180-1183, 2008.
8. Hao, Y. and C. G. Paini, "Isolation enhancement of anisotropic UC-PBG microstrip diplexer patch antenna," IEEE Antennas Wireless Propag. Lett., Vol. 1, No. 1, 135-137, 2002.
9. Fallahzadeh, S., H. Bahrami, A. Akbarzadeh, and M. Tayarani, "High-isolation dual-frequency operation patch antenna using spiral defected microstrip structure," IEEE Antennas Wirless Propag. Lett., Vol. 9, 122-124, 2010.
10. Lu, Y. C. and Y. C. Lin, "A mode-based design method for dual-band and self-diplexing antennas using double T-stubs loaded aperture," IEEE Antennas Wireless Propag. Lett., Vol. 60, 5596-5603, 2012.
11. Mukherjee, S. and A. Biswas, "Design of self-diplexing substrate integrated waveguide cavity backed slot antenna," IEEE Antennas Wireless Propag. Lett., Vol. 15, 1775-1778, 2016.
12. Lee, Y. J., J. H. Tarng, and S. J. Chung, "A filtering diplexing antenna for dual-band operation with similar radiation patterns and low cross-polarization levels," IEEE Antennas Wireless Propag. Lett., Vol. PP, No. 99, 1-1, 2016.
13. Hong, J. S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, New York, 2001.
14. Himdi, M. and J. P. Daniel, "Transmission line analysis of aperture-coupled microstrip antenna," Electron. Lett., Vol. 25, 1406-1408, 1989.
15. Bucci, O. M., T. Isernia, and A. F. Morabito, "Optimal synthesis of circularly symmetric shaped beams," IEEE Trans. Antennas Propagat., Vol. 62, No. 4, 1954-1964, 2014.