Reflection-Mode Bandstop Filters With Minimum Through-Line Length

This paper presents a technique that enables the design of high-order microwave bandstop filters with a total through-line length of significantly less than one quarter-wavelength at the filter center frequency. The total through-line length using this technique can be zero regardless of the filter order in theory, but it is limited in practice by the finite line length required to obtain a desired coupling magnitude between the through line and a resonator. A fifth-order quasi-elliptic reflection-mode bandstop filter design is shown with total through-line length of less than 1/15th of a wavelength in suspended-stripline technology. The measured response has a 42-MHz 30-dB bandwidth at a center frequency of 3 GHz and four reflection zeros. The bandstop filter design technique described in this paper shows great promise for reducing the size and weight of microwave bandstop filters.

[1]  H.C. Bell.  The Coupling Matrix in Low-Pass Prototype Filters , 2007, IEEE Microwave Magazine.

[2]  H. C. Bell.  L-resonator bandstop filters , 1996 .

[3]  Kai Chang,et al.  Compact second harmonic-suppressed bandstop and bandpass filters using open stubs , 2006, IEEE Transactions on Microwave Theory and Techniques.

[4]  W.M. Fathelbab,et al.  Synthesis of Cul-De-Sac Filter Networks Utilizing Hybrid Couplers , 2007, IEEE Microwave and Wireless Components Letters.

[5]  I. Hunter,et al.  Frequency-Selective Limiters Using Nonlinear Bandstop Filters , 2009, IEEE Transactions on Microwave Theory and Techniques.

[6]  R. Cameron.  Advanced coupling matrix synthesis techniques for microwave filters , 2003 .

[7]  Ying Wang,et al.  Direct-Coupled Realizations for Microwave Bandstop Filters , 2005, IEEE MTT-S International Microwave Symposium Digest, 2005..

[8]  R.V. Snyder,et al.  Bandstop filters with extended upper passbands , 2006, IEEE Transactions on Microwave Theory and Techniques.

[9]  Dimitrios Peroulis,et al.  High-Q tunable bandstop filters with adaptable bandwidth and pole allocation , 2011, 2011 IEEE MTT-S International Microwave Symposium.

[10]  U. Rosenberg,et al.  Direct synthesis of a new class of bandstop filters , 2004, IEEE Transactions on Microwave Theory and Techniques.

[11]  Ian Hunter,et al.  Triple mode dielectric resonator hybrid reflection filters , 1998 .

[12]  D. Pozar.  Microwave Engineering , 1990 .

[13]  R. Gomez-Garcia,et al.  Using the branch-line directional coupler in the design of microwave bandpass filters , 2005, IEEE Transactions on Microwave Theory and Techniques.

[14]  Ian Hunter,et al.  Synthesis of reflection-mode prototype networks with dissipative circuit elements , 1997 .

[15]  A. Guyette,et al.  Intrinsically Switched Varactor-Tuned Filters and Filter Banks , 2012, IEEE Transactions on Microwave Theory and Techniques.

[16]  Yo-Shen Lin,et al.  Millimeter-wave bandstop filter with absorptive stopband , 2014, 2014 IEEE MTT-S International Microwave Symposium (IMS2014).

[17]  G. L. Matthaei,et al.  Microwave Band-Stop Filters with Narrow Stop Bands , 1962 .