Design of miniaturized vertically stacked SIW filters in LTCC

Miniaturization techniques for the design of substrate integrated waveguide (SIW) filters in low temperature co-fired ceramic (LTCC) substrates are presented in this paper. The multilayer nature of LTCC technology enables three dimensional arrangements of filter cavities. Not only adjacent cavities but the cavity structure itself can be vertically stacked. Several novel coupling mechanisms for realizing both electrical and magnetic couplings with strong or low coupling strengths are proposed. Desired filter responses and specifications can be accomplished by properly choosing the proposed coupling structures. For a three pole Chebyshev filter, 88% size reduction can be achieved with fully stacked double folded resonators, compared to a planar version with traditional SIW cavities. On the other hand, 92% size reduction is also achieved for a four pole Chebyshev filter with vertically stacked quadruple folded resonators.