volume | PIER Journals

Abstract

A novel microstrip diplexer with high selectivity and isolation performance is proposed through the combination of two compact bandpass filters composed of open/shorted lines and an open stub, which are designed for LTE application. Six transmission zeros in the upper stopband are used to suppress the harmonic of the microstrip diplexer. The transmission zeros near the passband can be adjusted conveniently by only changing the electrical length of the open/shorted stubs. A diplexer prototype with two passbands at 1.8 GHz and 2.1 GHz is fabricated. The isolation between the two channels is greater than 40 dB from 0.1 to 6.5 GHz.

1. Cheng, F., X. Q. Lin, Z. B. Zhu, L. Y. Wang, and Y. Fan, "High isolation diplexer using quarter-wavelength resonator filter," Electron. Lett., Vol. 48, No. 6, 330-331, 2012.
doi:10.1049/el.2012.0031

2. Feng, W. J., X. Gao, and W. Q. Che, "Microstrip diplexer for GSM and WLAN bands using common shorted stubs," Electron. Lett., Vol. 50, No. 20, 1486-1488, 2014.
doi:10.1049/el.2014.2500

3. Chen, C. F., T. Y. Huang, C. P. Chou, and R. B. Wu, "Microstrip diplexers design with common resonator sections for compact size, but high isolation," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 5, 1945-1952, 2006.
doi:10.1109/TMTT.2006.873613

4. Srisathit, S., S. Patisang, R. Phromloungsri, S. Bunnjaweht, S. Kosulvit, and M. Chongcheawcham-nan, "High isolation and compact size microstrip hairpin diplexer," IEEE Microw. Wireless Compon. Lett., Vol. 15, No. 2, 101-103, 2005.
doi:10.1109/LMWC.2004.842839

5. Yang, T., P. L. Chi, and T. Itoh, "High isolation and compact diplexer using the hybrid resonators," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 10, 551-553, 2010.
doi:10.1109/LMWC.2010.2052793

6. Xue, Q. and J. X. Chen, "Compact diplexer based on double-sided parallel-strip line," Electron. Lett., Vol. 44, No. 2, 123-124, 2008.
doi:10.1049/el:20083117

7. Zeng, H. Y., G. M. Wang, D. Z. Wei, and Y. W. Wang, "Planar diplexer using composite right-/left-banded transmission line under balanced condition," Electron. Lett., Vol. 48, No. 2, 104-106, 2012.
doi:10.1049/el.2011.2763

8. Feng, W. J., W. Q. Che, Y. M. Chang, S. Y. Shi, and Q. Xue, "High selectivity fth-order wideband bandpass lter with multiple transmission zeros based on transversal signal-interaction concepts," IEEE Trans. Microw. Theory Techn., Vol. 61, No. 1, 89-97, 2013.
doi:10.1109/TMTT.2012.2227785

Dr. Wenjie Feng

Dr. Meiling Hong

Prof. Wenquan Che