A K-band LTCC SMD type balun using a multi-layer coupler insensitive to misalignment

An SMD type balun with a frequency range from 10 GHz to 25 GHz in a low temperature co-fired ceramic (LTCC) substrate is designed and measured. To reduce the effect of misalignment in the multilayer coupler, we propose a novel multilayer coupler structure which is insensitive to misalignment. The package has ports on the ground plane for the SMT, and a cover on top of the circuit to protect the circuit. Every transmission line is simulated as an embedded micro-strip line to account for the cover effect. All the internal ports are connected to the output ports at ground plane through via transition. The total number of LTCC layers is 5 including the cover layer. The overall dimension is as small as 5.5 mm × 5.5 mm × 0.5 mm.