Two compact differential bandpass filters (BPFs) based on coupled-line resonators and loaded capacitors are proposed in this work. By properly designing the coupled resonator and the loaded capacitance of original filter model, differential-mode (DM) passband responses and common-mode (CM) rejection can be obtained .For validation, two differential BPFs named Filter I and Filter II are discussed and experimentally characterized. One more DM transmission zero generated by out-of-phase cross-coupling is employed to control the DM bandwidth and sharpen the selectivity in Filter I while lumped capacitors are loaded in Filter II to replace capacitive coupled resonators for miniaturized size. Both filters are centered at 4.5 GHz with about 9% DM fractional bandwidth (FBW), less than 1.5 dB insertion loss, more than 15 dB return loss, and wideband CM suppression with more than 18 dB rejection. Furthermore, the size of Filter II is substantially smaller than Filter I and previously reported differential BPFs.
2. Hao, J. S. and Y. Wang, "Clutter suppression for ultra-wideband radar," Command Information System and Technology, Vol. 4, No. 3, 60-64, Jun. 2013.
3. Wang, X.-H., Q. Xue, and W.-W. Choi, "A novel ultra-wideband differential filter based on double-sided parallel-strip line," IEEE Microwave and Wireless Components Letters, Vol. 20, No. 8, 471-473, Aug. 2010.
doi:10.1109/LMWC.2010.2050869
4. Wang, X.-H., H. Zhang, and B.-Z. Wang, "A novel ultra-wideband differential filter based on microstrip line structures," IEEE Microwave and Wireless Components Letters, Vol. 23, No. 3, 128-130, Mar. 2013.
doi:10.1109/LMWC.2013.2243719
5. Wu, X.-H. and Q.-X. Chu, "Compact differential ultra-wideband bandpass filter with common-mode suppression," IEEE Microwave and Wireless Components Letters, Vol. 22, No. 9, 456-458, Sep. 2012.
doi:10.1109/LMWC.2012.2213075
6. Lim, T.-B. and L. Zhu, "A differential-mode wideband bandpass filter on microstrip line for UWB application," IEEE Microwave and Wireless Components Letters, Vol. 19, No. 10, 632-634, Oct. 2009.
7. Lim, T.-B. and L. Zhu, "Highly selective differential-mode wideband bandpass filter for UWB application," IEEE Microwave and Wireless Components Letters, Vol. 21, No. 3, 133-135, Mar. 2011.
doi:10.1109/LMWC.2011.2104357
8. Zhu, H.-T., W.-J. Feng, W.-Q. Che, and Q. Xue, "Ultra-wideband differential bandpass filter based on transversal signal-interference concept," IET Electronics Letters, Vol. 47, No. 18, 1033-1035, Sep. 2011.
doi:10.1049/el.2011.2088
9. Feng, W.-J., W.-Q. Che, Y.-L. Ma, and Q. Xue, "Compact wideband differential bandpass filters using half-wavelength ring resonator," IEEE Microwave and Wireless Components Letters, Vol. 23, No. 2, 81-83, Feb. 2013.
doi:10.1109/LMWC.2013.2239632
10. Naqui, J., A. Fernandez-Prieto, M. Duran-Sindreu, F. Mesa, J. Martel, F. Medina, and F. Martin, "Common-mode suppression in microstrip differential lines by means of complementary split ring resonators: Theory and application," IEEE Transactions on Microwave Theory and Techniques, Vol. 60, No. 10, 3023-3034, Oct. 2012.
doi:10.1109/TMTT.2012.2209675
11. Velez, P., J. Naqui, A. Fernandez-Prieto, M. Duran-Sindreu, J. Bonache, J. Martel, F. Medina, and F. Martin, "Differential bandpass filter with common-mode suppression based on open split ring resonators and open complementary split ring resonators," IEEE Microwave and Wireless Components Letters, Vol. 23, No. 1, 22-24, Jan. 2013.
doi:10.1109/LMWC.2012.2236083
12. Feng, W.-J., W.-Q. Che, T.-F. Eibert, and Q. Xue, "Compact wideband differential bandpass filter based on the double-sided parallel-strip line and transversal signal-interaction concepts," IET Microwave, Antennas & Propagation, Oct. 2011.
13. Feng, W.-J. and W.-Q. Che, "Novel wideband differential bandpass filters based on T-shaped structure," IEEE Transactions on Microwave Theory and Techniques, Vol. 60, No. 6, 1560-1568, Jun. 2012.
doi:10.1109/TMTT.2012.2188538
14. Wang, H., K.-W. Tam, S.-K. Ho, and W. Wu, "A novel compact capacitive loaded differential bandpass filter," Asia-Pacific Microwave Conference, 933-935, Seoul, Korea, 2013.
15. Wang, H., K.-W. Tam, W.-W. Choi, W.-Y. Zhuang, S.-K. Ho, W. Kang, and W. Wu, "Analysis of coupled cross-shaped resonator and its application to differential bandpass filters design," IEEE Transactions on Microwave Theory and Techniques, Vol. 62, No. 12, 2942-2953, Dec. 2014.
doi:10.1109/TMTT.2014.2364814
16. Available: http://www.dilabs.com, .
doi:10.1109/TMTT.2014.2364814
17. Matthaei, G.-L., L. Young, and E.-M.-T. Jones, Microwave Filters, Impedance-matching Networks, and Coupling Structures, Artech House, Chapter 5, Norwood, MA, USA, 1985.
18. Alley, G. D., "Interdigital capacitors and their application to lumped-element microwave integrated circuits," IEEE Transactions on Microwave Theory and Techniques, Vol. 18, No. 12, 1028-1033, Dec. 1970.
doi:10.1109/TMTT.1970.1127407
19. Pettenpaul, E., H. Kapust, A. Weisgerber, H. Mampe, J. Luginsland, and I. Wolff, "CAD models lumped elements on GaAs up to 18 GHz," IEEE Transactions on Microwave Theory and Techniques, Vol. 36, No. 2, 294-304, Feb. 1988.
doi:10.1109/22.3518
Submit
