Novel compact parallel-coupled microstrip bandpass filters with lumped-element K-inverters

Novel compact parallel-coupled microstrip bandpass filters are proposed by using additional lumped inductors to realize K-inverters between coupled-line sections to achieve an equivalent to the quarter-wavelength (/spl lambda//4) resonator filters. As a result, the filter order can be doubled without increasing the circuit area, and no repeated passband is observed at twice the center frequency. In addition, by introducing the cross-coupling effect, two transmission zeros at upper and lower stopbands may be created. Simple equivalent-circuit models are also established as effective design tools. Specifically, several compact fourth-order microstrip bandpass filters with good stopband rejection are implemented and carefully examined.

[1]  Md.C. Velazquez-Ahumada,et al.  Parallel coupled microstrip filters with ground-plane aperture for spurious band suppression and enhanced coupling , 2004, IEEE Transactions on Microwave Theory and Techniques.

[2]  Jr. R. Wyndrum.  Microwave filters, impedance-matching networks, and coupling structures , 1965 .

[3]  J. Kuo,et al.  Design of parallel-coupled microstrip filters with suppression of spurious resonances using substrate suspension , 2004, IEEE Transactions on Microwave Theory and Techniques.

[4]  Txema Lopetegi,et al.  New microstrip "Wiggly-Line" filters with spurious passband suppression , 2001 .

[5]  Chi-Yang Chang,et al.  A novel coupling structure suitable for cross-coupled filters with folded quarter-wave resonators , 2003, IEEE Microwave and Wireless Components Letters.

[6]  Chi-Hsueh Wang,et al.  Novel inductance-incorporated microstrip coupled-line bandpass filters with two attenuation poles , 2004, 2004 IEEE MTT-S International Microwave Symposium Digest (IEEE Cat. No.04CH37535).

[7]  T. Itoh,et al.  A modified parallel-coupled filter structure that improves the upper stopband rejection and response symmetry , 1991 .

[8]  I. J. Bahl.  Capacitively compensated high performance parallel coupled microstrip filters , 1989, IEEE MTT-S International Microwave Symposium Digest.

[9]  W. Menzel,et al.  Compact microstrip bandpass filter with two transmission zeros using a stub-tapped half-wavelength line resonator , 2003, IEEE Microwave and Wireless Components Letters.

[10]  S. Cohn.  Parallel-Coupled Transmission-Line-Resonator Filters , 1958 .

[11]  Ruey-Beei Wu,et al.  Highly Selective Microstrip Bandpass Filters in Ka-Band , 2002, 2002 32nd European Microwave Conference.

[12]  A. Riddle.  High performance parallel coupled microstrip filters , 1988, 1988., IEEE MTT-S International Microwave Symposium Digest.

[13]  Jen-Tsai Kuo,et al.  Microstrip stepped impedance resonator bandpass filter with an extended optimal rejection bandwidth , 2003 .

[14]  B. Easter,et al.  Parallel-Coupled-Line Filters for Inverted-Microstrip and Suspended-Substrate MIC's , 1981, 1981 11th European Microwave Conference.

[15]  M. Makimoto,et al.  Bandpass Filters Using Parallel Coupled Strip-Line Stepped Impedance Resonators , 1980, 1980 IEEE MTT-S International Microwave symposium Digest.

[16]  Yo-Shen Lin,et al.  Novel Balanced Microstrip Coupled-Line Bandpass Filters , 2004 .

[17]  Jen-Tsai Kuo,et al.  Parallel-coupled microstrip filters with over-coupled end stages for suppression of spurious responses , 2003, IEEE Microwave and Wireless Components Letters.

[18]  A. E. Ruehii.  Inductance Calculations in a Complex Integrated Circuit Environment , 2002 .

[19]  Chi-Yang Chang,et al.  Miniaturized microstrip cross-coupled filters using quarter-wave or quasi-quarter-wave resonators , 2003 .