Hello I have two resonant circuits (tuned to the same frequency) that are magnetically coupled to each other via two coils placed paralell to each other. (energy and data is transferred from one circuit to another) Now, I know that the coupling between the two can be overcoupled, undercoupled or critically coupled, and that maximum powetransfer occurrs as the circuits are critically coupled. If I have understood correctly, the coupling type is determined exclusively by geometrical factors, i.e. distance between the two coils and their orientation and size with respect to each other. For two paralell, fixed sized coils, there should therefore be an optimal distance between the coils that gives two critically coupled circuits. I am not sure how to calculte this distance. Do anyone have a tip or maybe a link to some good material on this subject. regards t.