Multi-layer coupled band-pass filter for 60 GHz LTCC system-on-package

We have developed a design method for space-saving and wide passband band-pass filter (BPF) for 60-GHz band applications. The BPF comprises multilayer-coupled stripline resonators on a multilayer low temperature co-fired ceramic (LTCC) substrate and can be highly integrated into a millimeter-wave system-on-package that is suitable for 60 GHz-band wireless communication applications. The proposed design method provides compactness and wide passband characteristics under fabrication accuracy limitation. The prototype filter is fabricated on a six-layer 50-μm LTCC substrate. A fabricated prototype BPF circuit achieves a passband of 54-66 GHz, which is suitable for 60 GHz channels. We also clarified that the displacements between layers of the LTCC multilayer substrate caused during its fabrication degraded its characteristics only slightly.