A miniaturized wideband complementary LTCC diplexer based on transmission lines and lumped elements

This paper presented a design and simulation result of a miniaturized complementary diplexer realized by low-temperature co-fired ceramic (LTCC) technology. The diplexer consisted of two pass-bands, a central frequency of 1.175 GHz with bandwidth of 46.8% and a central frequency of 1.925 GHz with bandwidth of 28.6% respectively. In the presented structure, we used transmission lines to realize the characteristics of lower pass-band, while lumped circular inductors were adopted to achieve the requirements of upper pass-band. The interaction of the two filters was handled very well by using a complementary schematic. We managed to make the VSWR on the antenna port less than 1.7. The final three-dimensional model occupied a volume of 3.2 × 2.5 × 1.95-mm.