Design of A Compact Broadband Microstrip Line Diplexer for VHF/UHF Frequency Range

In this paper, a compact broadband microstrip line diplexer for VHF/UHF frequency range is proposed. For miniaturization, lumped capacitance and curved microstrip lines acting as inductance are utilized to construct the diplexer. The two filters are located on two substrates and connected by an approximate coaxial line structure. The working bandwidth is 0.1 to 2.5 GHz. The transition bandwidth is from 0.902 to 0.967 GHZ. The final size of the combiner is just as small as
$0.07\lambda_{0}\times 0.16 \lambda_{0}= 1.3$
GHz. Simulation results show the verification of the proposed structure.