“…In past, many design methods for planar diplexer have been proposed. The most well‐known methods to compact the planar diplexer is using resonators such as double‐loop‐coupled and slow‐wave open‐loop resonators , modified stepped‐impedance resonator , spiral resonator , periodic‐stub resonator , square open loop with stepped‐impedance resonator , stepped impedance coupled‐line resonator , H‐type resonator , and artificial transmission line , microstrip line resonators with loaded elements , have been utilized in diplexer design. In , microstrip diplexer based on conventional complementary split ring and pseudo‐interdigital resonators are also designed to reduce the size of diplexer, but the size is still large.…”