Wide band balun filter using open/shorted coupled line sections

Out of phase equal power division and bandpass filtering functionalities are combined within a single circuit element over a wide bandwidth. This is achieved in the proposed structure by the use of open/shorted coupled line sections. A balun band pass filter (BPF) with a wide bandwidth of 40% is realized to validate the feasibility of the proposed structure. The measured results agree well with simulation, exhibiting small amplitude, and phase imbalance at the output ports throughout the desired passband, together with good rejection elsewhere. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1099–1101, 2015