End coupled stripline BPF using LTCC in millimeter-wave

End coupled stripline BPF using LTCC process in millimeter-wave was designed and fabricated. To design end coupled stripline BPF, the bandgaps of horizontal coupling structure and vertical coupling structure were modeled with w-type capacitance. The bandgap models were verified by a full-wave electromagnetic simulation program. To test a fabricated filter, CPWG-to-stripline transitions were used in input and output ports. To evaluate the validity of this technique, order-3 Chebyschev BPF centered at 44.2 GHz with a 5% fractional bandwidth (FBW) was used. According to design and measurement results, a performance of insertion loss of 3.6 dB and return loss of 18 dB is achieved at full input/output ports, total size of the filter is 512 × 3000 × 8000 μm.