Design of Vertically Stacked Waveguide Filters in LTCC

• Published in: IEEE transactions on microwave theory and techniques Vol. 55; no. 8; pp. 1771 - 1779
• Main Authors: Shen, Tze-Min, Chen, Chi-Feng, Huang, Ting-Yi, Wu, Ruey-Beei
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.08.2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Band pass filters; Bandpass filter; cavity; Ceramics; Circuit properties; Coupling circuits; coupling coefficient; Cross coupling; Electric fields; Electric filters; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency; Frequency filters; Holes; low-temperature co-fired ceramic (LTCC); Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Millimeter wave technology; Multilayers; Nonhomogeneous media; Oscillators, resonators, synthetizers; Planar waveguides; quasi-elliptic function; Resonator filters; Resonators; Space technology; stacked vias; Walls; Waveguide filters; Stack filter; Selectivity; low- temperature co-fired ceramic (LTCC); Flexibility; Bandpass filter; Cavity; quasi-elliptic function; Band pass filter; Cavity resonator; Ceramic materials; Low temperature; Waveguide filters; Waveguide resonator; Multivariable control; Resonator filters; Multiple layer; Compact design; Electric field; Planar waveguide; Simulation; stacked vias; Coupling coefficient; Miniaturization; Piezoelectric resonator; Comparative study; Coupled resonator; Planar technology
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2007.902080

This paper proposes four-pole quasi-elliptic function bandpass waveguide filters using multilayer low-temperature co-fired ceramic technology. The vertical metal walls of the waveguide resonators are realized by closely spaced metallic vias. Adjacent cavities are coupled by a narrow slot at the edge of the common broad wall or an inductive window on the sidewall. Two types of vertical coupling structures are utilized to achieve the cross coupling between nonadjacent resonators at different layers. With multilayer capability, there is more flexibility to arrange the cavities of coupled resonator filters in 3-D space. It is demonstrated by both the simulation and experiment that the proposed filter structures occupy a compact circuit area and have good selectivity. The filter with electric field cross coupling occupies a half area of a planar four-pole waveguide filter, while the filter with stacked vias cross coupling has 65% size reduction in comparison with a planar waveguide filter.