Introductions about Microstrip Couplers and Power Splitters

Microstrip couplers and power splitters are widely used electrical components in the field of microwave technology, which has the function of dividing one wave into multiple waves with same magnitudes but different phases. In this essay, 5 typical types of couplers and power splitters are introduced, with their applications, layout designs, effect on the wave, advantages and weaknesses. Couplers and power splitters are labelled with their output wave phase differences and their voltage magnitude transfer ratio. In this essay, all the couplers introduced are 3dB couplers, which means that the output voltage is decreased by 3dB. The Wilkinson power splitter has an output phase difference of 0 degree, the monolithic multilayer 2-line microstrip directional coupler, the Lange coupler, the microstrip branch-line coupler have output phase difference of 90 degrees, and the planar Marchand balun has output phase difference of 180 degrees. The microstrip rat-race coupler has 2 divider modes and 1 combiner mode, where in the divider mode the phase difference could be set as 0 degree or 180 degrees. Therefore, in the design of microwave circuits, the type of coupler should be carefully chosen according to the working characteristics, the structure features and the working conditions of couplers. (paper)