A Novel Capacitive Cross - Coupling for Enhancement of Microwave Cavity Filter
Main Article Content
Abstract
Since the difficulties in tuning the transmission zero point of microwave cavity filter, one enhancement capacitive cross-coupling structure is proposed. This structure is implemented by adding a new tap screw to the centre of supporting Teflon piece of cross coupling dumpbell. Thus a new distributed variable capacitor is generated. The capacitive cross coupling factor is achieved greater value, so the slope of cavity filter is improved. More over, the position of transmission zero point can be tuned after assembly by varying the length of the screw. The simulation results show that cross coupling bandwidth can be changed about 4.6 MHz when the screw high changing 7 mm. This new proposed structure is applied to a microwave cavity filter in eNodeB for Band 3 – Long Term Evolution (LTE) application to verify the effectiveness. The filter is made up of 10 coaxial resonator cavities with two new capacitive cross-couplings. The simulation results of filter fully meets specification requirements including band of 1805 to 1880 MHz, return loss below −12.7 dB, ripple of 0.1 dB and insertion loss below 0.2 dB. The signal rejection at frequencies below 20 MHz bandwidth is improved of 1 dB. More over, this structure can be developed not only in Band 3 but also in different bands when using resonator cavity filter type.
Keywords
Cavity filter, resonator, cross-coupling, band-pass filter, screw
Article Details
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
References
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[2] Jia-Sheng Hong, Microstrip Filters for RF/Microwave Applications, Wiley Series in Microwave and Optical Engineering, Hoboken, New Jersey, John Wiley & Sons, Inc, 2011 https://doi.org/10.1002/9780470937297
[3] B. Mohajer-Iravani and M. A. EL Sabbagh, High-selective wideband combline filters based on miniaturized-engineered resonators, interresonator tapped-in coupling, and probe coupling, 2012 IEEE Radio and Wireless Symposium, Santa Clara, CA, 2012 https://doi.org/10.1109/RWS.2012.6175330
[4] Zhengjun Du, Jin Pan, Ma Boyuan, Xinyang Ji, Deqiang Yang, A novel capacitive cross-coupling structure for ceramic-filled cavity filters, IEEE Access, vol. 9, pp: 27201 – 27209, 09 February 2021. https://doi.org/10.1109/ACCESS.2021.3058194
[5] Sai Li, Xuedao Wang, Yi Li, and Jianpeng Wang, Design of compact coaxial cavity bandpass filter with high selectivity, 2019 IEEE MTT-S International Microwave Biomedical Conference (IMBioC), Nanjing, China, 6-8 May 2019 https://doi.org/10.1109/IMBIOC.2019.8777891
[6] Muhamad Latif, Giuseppe Macchiarella and Farooq Mukhtar, A novel coupling structure for inline realization of cross-coupled rectangular waveguide filters, IEEE Access, vol.8, pp. 107527 – 107538, 2020 https://doi.org/10.1109/ACCESS.2020.3000847
[7] Alexander Zakharov, Sergii Rozenko, and Michael Ilchenko, Two types of trisection bandpass filters with mixed cross-coupling, IEEE Microwave and Wireless Components Letter, Volume 28, Issue 7, July 2018 https://doi.org/10.1109/LMWC.2018.2837905
[8] G. L. Matthaei, L. Young, and E. M. T. Jones, Microwave Filters, Impedance-Matching Networks and Coupling Structures. New York, McGraw-Hill, 1964. https://doi.org/10.21236/AD0402930
[9] Larry D. Paarmann, Design and Analysis of Analog Filters: A Signal Processing Perspective, Springer US, 2003
[10] I.C. Hunter, Theory and design of microwave filters. Stevenage, U.K. IEEE IET Electromagnetic Waves Series 48, 2001, p.60. https://doi.org/10.1049/PBEW048E
[11] J.-S. Hong, M. J. Lancaster, Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters, IEEE Trans. Microw. Theory Techn., vol. 44, no. 11, pp. 2099–2109, Nov. 1996. https://doi.org/10.1109/22.543968
[12] R. J. Vidmar. (August 1992). On the use of atmospheric plasmas as electromagnetic reflectors. IEEE Trans. Plasma Sci.
[13] Dhanasekharan Natarajan (2013), A Practical Design of Lumped, Semi-Lumped and Microwave Cavity Filters: Lecture Notes in Electrical Engineering, Springer. https://doi.org/10.1007/978-3-642-32861-9
[14] Hoft, Michael, Tunable capacitive coupling for cavity resonator filters, 2009 German Microwave Conference, Munich. https://doi.org/10.1109/GEMIC.2009.4815881