Antenna phasing with Butler Matrix
A Butler matrix is a method of dividing power amongst a set of loads while maintaining a certain phase progression between the output signals. It finds its most useful applications in the phasing of antenna arrays. This PDF document describes the development of a 4 element linear array using 3 dB quadrature hybrids. Application of an signal to one of the inputs will cause the radiation of a signal in a fixed direction. In effect, this allows one to choose from one of four beam directions by merely switching the input. Also, if the antennas are matched to the feeding transmission line, all the inputs will be isolated from one another by virtue of the isolation properties of the hybrid.