Interaction features of stepped-impedance stripline resonators in comb filters

Alexander V. Zakharov; Mykhailo Ye. Ilchenko; Ludmila S. Pinchuk

doi:10.3103/S073527271801003X

Authors

Alexander V. Zakharov Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0002-1222-1623
Mykhailo Ye. Ilchenko Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0002-5518-5992
Ludmila S. Pinchuk Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0002-1893-3365

DOI:

https://doi.org/10.3103/S073527271801003X

Keywords:

сombline filter, mixed coupling coefficient, transmission zero, frequency response, stripline construction, stepped-impedance resonator

Abstract

Mixed coefficients of coupling between the closely spaced stepped-impedance resonators in comb filters of stripline design have been investigated. Transmission zeros at frequencies f_zi correspond to mixed coupling coefficients k_i. These zeros can be moved with respect to the filter passband central frequency f₀ by modifying the shape of resonators. It was proved that the reduction of gap between resonators made it possible to locate frequencies f_z and f₀ closer to one another. The existing restrictions on the minimal value of gap between resonators limit the degree of proximity between f_z and f₀. The N-resonator stripline comb filters with mixed coupling can have N – 1 transmission zeros. The absence of cross-coupling links in stripline filters simplifies their construction. It has been established that the thickness of central conductors of stripline resonators affects the positive and negative mixed coupling coefficients. The paper presents measurement data of miniature stripline three-resonator comb filter having an enhanced selectivity at the expense of two transmission zeros. The central frequency of filter is f₀ = 1850 MHz, the bandwidth BW = 100 MHz. The filter having dimensions 5.8x4.2x2 mm was implemented by connecting two ceramic substrates having relative dielectric permittivity e_r = 92 and the metallized patterns deposited on them.

References

MATTHAEI, G.L.; YOUNG, L.; JONES, E.M.T. Microwave Filters, Impedance-Matching Networks, and Coupling Structures. Artech House, 1980.

HONG, J.-S. Microstrip Filters for RF/Microwave Application, 2nd ed. John Wiley & Sons, Inc., 2011.

ZAKHAROV, A.V.; ILCHENKO, M.Y.; KARNAUH, V.Y.; PINCHUK, L.S. Tunable microstrip resonators with ferroelectric capacitors. Radioelectron. Commun. Syst., v.53, n.8, p.418-423, 2010. DOI: https://doi.org/10.3103/S0735272710080042.

ZAKHAROV, A.V.; IL’CHENKO, M.E.; KARNAUKH, V.Y.; PINCHUK, L.S. Quality of ferroelectric capacitors used in tunable microwave filters. J. Commun. Technol. Electron., v.56, n.8, p.1020, 2011. DOI: https://doi.org/10.1134/S1064226911050147.

MAKIMOTO, M.; YAMASHITA, S. Microwave Resonators and Filters for Wireless Communication. Springer Science & Business Media, 2001.

YEUNG, L.K.; WU, K.-L.; WANG, Y.E. Low-temperature cofired ceramic LC filters for RF applications. IEEE Microwave Mag., v.9, n.5, p.118-128, Oct. 2008. DOI: https://doi.org/10.1109/MMM.2008.927634.

ZHU, F.; HONG, W.; CHEN, J.-X.; WU, K. Quarter-wavelength stepped-impedance resonator filter with mixed electric and magnetic coupling. IEEE Microwave Wireless Components Lett., v.24, n.2, p.90-92, Feb. 2014. DOI: https://doi.org/10.1109/LMWC.2013.2290225.

ZAKHAROV, A.V.; IL’CHENKO, M.E.; KORPACH, V.N. Features of the coupling coefficients of planar stepped-impedance resonators at higher resonance frequencies and application of such resonators for suppression of spurious passbands. J. Commun. Technol. Electron., v.59, n.6, p.550-556, 2014. DOI: https://doi.org/10.1134/S1064226914060217.

CAMERON, R.J. General coupling matrix synthesis methods for Chebyshev filtering functions. IEEE Trans. Microwave Theory Tech., v.47, n.4, p.433-442, Apr. 1999. DOI: https://doi.org/10.1109/22.754877.

THOMAS, J.B. Cross-coupling in coaxial cavity filters – a tutorial overview. IEEE Trans. Microwave Theory Tech., v.51, n.4, p.1368-1376, Apr. 2003. DOI: https://doi.org/10.1109/TMTT.2003.809180.

ZHANG, S.; ZHU, L.; LI, R. Compact quadruplet bandpass filter based on alternative J/K inverters and l/4 resonators. IEEE Microwave Wireless Compon. Lett., v.22, n.5, p.224-226, May 2012. DOI: https://doi.org/10.1109/LMWC.2012.2193124.

WANG, H.; CHU, Q.-X. An inline coaxial quasi-elliptic filter with controllable mixed electric and magnetic coupling. IEEE Trans. Microwave Theory Tech., v.57, n.3, p.667-673, 2009. DOI: https://doi.org/10.1109/TMTT.2009.2013290.

TANG, C.-W.; YOU, S.-F. Design metodologies of LTCC bandpass filters, diplexer, and triplexer with transmission zeros. IEEE Trans. Microwave Theory Tech., v.54, n.2, p.717-723, Feb. 2006. DOI: https://doi.org/10.1109/TMTT.2005.862638.

MA, K.; MA, J.-G.; YEO, K.S.; DO, M.A. A compact size coupling controllable filter with separate electric and magnetic coupling paths. IEEE Trans. Microwave Theory Tech., v.54, n.3, p.1113-1119, Mar. 2006. DOI: https://doi.org/10.1109/TMTT.2005.864118.

CHU, Q.-X.; WANG, H. A compact open-loop filter with mixed electric and magnetic coupling. IEEE Trans. Microwave Theory Tech., v.56, n.2, p.431-439, Feb. 2008. DOI: https://doi.org/10.1109/TMTT.2007.914642.

ZHANG, S.; ZHU, L.; WEERASEKERA, R. Synthesis of inline mixed coupled quasi-elliptic bandpass filters based on l/4 resonators. IEEE Trans. Microwave Theory Tech., v.63, n.10, p.3487-3493, Oct. 2015. DOI: https://doi.org/10.1109/TMTT.2015.2467380.

ZAKHAROV, A.V. Stripline combline filters on substrates designed on high-permittivity ceramic materials. J. Commun. Technol. Electron., v.58, n.3, p.265-272, 2013. DOI: https://doi.org/10.1134/S1064226913030145.

ZAKHAROV, A.V.; ILCHENKO, M.Y.; PINCHUK, L.S. Coupling coefficient of quarter-wave resonators as a function of parameters of comb stripline filters. Radioelectron. Commun. Syst., v.58, n.6, p.284-289, 2015. DOI: https://doi.org/10.3103/S0735272715060060.

ZAKHAROV, A.V.; IL’CHENKO, M.E. Pseudocombline bandpass filters based on half-wave resonators manufactured from sections of balanced striplines. J. Commun. Technol. Electron., v.60, n.7, p.801-807, 2015. DOI: https://doi.org/10.1134/S1064226915060182.

ZAKHAROV, A.V.; ILCHENKO, M.Y.; PINCHUK, L.S. Coupling coefficients of step-impedance resonators in stripeline band-pass filters of array type. Radioelectron. Commun. Syst., v.57, n.5, p.217-223, 2014. DOI: https://doi.org/10.3103/S0735272714050045.

VOL’MAN, V.I. (ed.). Reference Book on Calculation and Designing of Microwave Stripline Devices [in Russian].Moscow: Radio i Svyaz’, 1982.

FEL’DSHTEIN, A.L. (ed.). Reference Book on Elements of Microstrip Technology [in Russian]. Moscow: Svyaz’, 1979.