Compact microstrip diplexer with differential outputs

A novel microstrip diplexer with differential outputs that is designed using half-wavelength open-loop resonators is investigated. The proposed diplexer combines two functions, i.e. diplexing operation and a balun, into one circuit, resulting in a very compact module. The design method is elucidated, with a prototype demonstrated. Measurements were conducted to verify the theoretical prediction. © 2010 The Institution of Engineering and Technology.