Wide tuning-range planar filters using lumped-distributed coupled resonators

This paper describes a discretely tunable filter topology based on lumped-distributed coupled transmission lines, particularly suitable for microelectromechanical systems switching devices. This topology is capable of simultaneous wide-band center frequency and bandwidth tuning, limited only by the electrical size of the transmission lines and the placement density of the switching devices. Low fractional bandwidths can be achieved without the need for large coupled-line spacings due to the antiphase relationship of the lumped capacitive and distributed electromagnetic coupling coefficients. The positions of the additional poles of attenuation due to the lumped capacitive coupling can be selected either above or below band leading to the choice of a narrow bandwidth design having good high-side performance or a design with compromised upper stopband performance, but with no bandwidth tuning limitations. The interaction between a pair of lumped-distributed coupled transmission lines is analyzed and the resulting model is used to develop a filter synthesis procedure. The synthesis procedure and filter performance are validated through theoretical and experimental comparisons using a filter with low-side attenuation poles

[1]  Mark A Beach,et al.  Miniature distributed filters for software re-configurable radio applications , 2002 .

[2]  Jiasheng Hong,et al.  Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters , 1996 .

[3]  A. Malczewski,et al.  RF MEMS‐based tunable filters , 2001 .

[4]  R. Mongia.  RF and microwave coupled-line circuits , 1999 .

[5]  C. Quendo,et al.  Bandwidth and central frequency control on tunable bandpass filter by using MEMS cantilevers , 2003, IEEE MTT-S International Microwave Symposium Digest, 2003.

[6]  Roop L. Mahajan,et al.  Applications of knowledge‐based artificial neural network modeling to microwave components , 1999 .

[7]  R.M. Young,et al.  Low-loss bandpass RF filter using MEMS capacitance switches to achieve a one-octave tuning range and independently variable bandwidth , 2003, IEEE MTT-S International Microwave Symposium Digest, 2003.

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

[9]  C. Rauscher.  Reconfigurable bandpass filter with a three-to-one switchable passband width , 2003 .

[10]  Robert L. Borwick,et al.  Variable MEMS capacitors implemented into RF filter systems , 2003 .

[11]  Mark A Beach,et al.  Tunable lumped-distributed capacitively-coupled transmission-line filter , 2004 .

[12]  Mark A Beach,et al.  A MEMS-ready wide tuning range planar resonator with application to microwave flexible filters , 2003 .

[13]  Mark A. Beach,et al.  Software defined radio receiver test-bed , 2001, IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211).

[14]  Yu Liu,et al.  Distributed MEMS transmission lines for tunable filter applications , 2001 .

[15]  C. A. Hall,et al.  VHF high‐power tunable RF bandpass filter using microelectromechanical (MEM) microrelays , 2001 .

[16]  S. Cohn.  Direct-Coupled-Resonator Filters , 1957, Proceedings of the IRE.