Second order dual-path coupled line filter

An original filter topology based on dual-path parallel coupled-lines is presented. Two identical coupled-lines are combined in parallel to result in a wideband bandpass response. Two transmission zeros are also resulted thanks to the cancellation effect in the dual-path connection. It is also shown that the use of asymmetrical coupled lines helps in giving more flexibility in obtaining higher coupling for better in-band matching. The proposed concept is tested using microstrip technology on FR4 substrate. Simulation and measurement results are presented in this paper to show its feasibility.