magic tee (or magic T or hybrid tee) is a hybrid or 3 dB coupler used in microwave systems. It is an alternative to the rat-race coupler. In contrast to the rat-race, the three-dimensional structure of the magic tee makes it less readily constructed in planar technologies such as microstrip or stripline.
The magic tee was originally developed in World War II, and first published by W. A. Tyrell (of Bell Labs) in a 1947 IRE paper.[1] Robert L. Kyhl and Bob Dicke independently created magic tees around the same time.