Design of Microwave Microstrip Multiband Diplexers for System in Package

Two microstrip multiband diplexers are investigated in this paper. The diplexers consist of channel bandpass filters and long feeding lines. Every bandpass filter controls one respective channel characteristic resulting in a high design freedom. The channel filters are fed through long microstrip feeding lines with good isolating property. The proposed method is then time-saving in comparison with previous ones. To validate the design concept, four- and six-channel diplexers are designed, fabricated, and tested.