Magic tee

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.

This allows it to be used as a duplexer; for instance, it can be used to isolate the transmitter and receiver in a radar system while sharing the antenna.

In practical examples, it is used to both isolate circuits and mix signals, for instance in a COHO radar.

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.

[2] Robert L. Kyhl and Bob Dicke independently created magic tees around the same time.

Dependence on the matching structure means that the magic tee will only work over a limited frequency band.

[3] Thus, with the ports numbered as shown, and to within a phase factor, the full scattering matrix for an ideal magic tee is (the signs of the elements in the fourth row and fourth column of this matrix may be reversed, depending on the polarity assumed for port 4).