With the rapid development of modern network and wireless communication technology,various network equipment and electronic products can communicate through the wireless access network, all of this must depend on the critical RF module and RF components. Now days so many electronic equipments in various fields are developing toward the miniaturization, multi-function and high performance direction. In order to realize the miniaturization of wireless systems and electronic products, occupy a larger volume of RF and microwave components the need to achieve miniaturization.
In this thesis, a novel enhanced balun bandpass filter with extremely small size and high isolation is demonstrated utilizing the combination of diagonally shorted coupled lines and parallel end shorted coupled lines both with shunt lumped capacitors and parallel-strip phase inverter. The coupled lines with shunt lumped capacitors can be used to largely reduce the required electrical length of transmission line. And the parallel-strip phase inverter is utilized to realize the balanced matching and isolation. Comparing with the typical Marchand Balun, it not only has excellent performance but also has no need to add any other resistive network between the outputs.