Ka-Band LTCC Stacked Substrate Integrated Waveguide Bandpass Filter

A Ka-band substrate integrated waveguide bandpass filter has been designed and fabricated using low temperature co-fired ceramic (LTCC) technology. The in-house developed SICCAS-K5F3 material with a permittivity of 6.2 and a loss tangent of 0.002 was used. The size and surface area of the proposed bandpass filter are reduced by exploiting vertical coupling in vertically laminated three-dimensional structures. The coupling between adjacent cavities is realized by a narrow slot. A vertical transition structure between the coplanar-waveguide feed line and the substrate integrated waveguide is adopted to facilitate the internal signal connection. The demonstrated third-order filter has a compact size of 6.79 mm×4.13 mm×1.34 mm (0.63λ0  × 0.38λ0  × 0.12λ0) and exhibits good performance with a low insertion loss of 1.74 dB at 27.73 GHz and a 3 dB fractional bandwidth of 10 %.