A rat-race coupler, also known as a hybrid ring coupler, is a type of coupler used in RF and microwave systems. In its simplest form, it is a 3 dB coupler and is thus an alternative to a magic tee. Compared to the magic tee, it has the advantage of being easy to realize in planar technologies such as microstrip and stripline, although waveguide rat races are also practical. Unlike magic tees, a rat-race needs no matching structure to achieve correct operation.