Broadband filter based on stub-loaded ridge substrate integrated waveguide (SIW) in low temperature cofired ceramic (LTCC)

A new broadband bandpass filter is proposed using stub-loaded ridge substrate integrated waveguide (SIW). The ridge SIWs loaded with and without stubs play the roles of resonators and inductive coupling structures, respectively. Since the cutoff frequency of ridge SIW is designed within the passband, both its propagating and evanescent modes are utilized to provide a strong coupling over the whole passband. The proposed filter has a multilayer configuration and can be fabricated with a standard low temperature cofired ceramic (LTCC) technology. In order to validate our design, a LTCC filter prototype is developed with a central frequency of 19 GHz and a fractional bandwidth of 40%. It has a compact volume of 6.89×2.85×0.79 mm³ and a low measured in-band insertion loss of 1.2 dB. The good performance of our proposed SIW filter has been demonstrated by the reasonable agreement obtained between the simulated and measured S-parameters. Its potential application for system in package is expected.