0°, 90°, and 180° Passive Power Dividers

The properties of directional couplers are almost exclusively expressed in terms of the scattering matrix, and this is the approach adopted in this chapter. One useful power divider met in microwave engineering is the Wilkinson three‐port circuit. The directional coupler is a four‐port circuit having an input port, two mutually isolated output ports, and one port isolated from the input port. One of the simplest variable power dividers is obtained by placing a variable phase‐shifter between two 3 dB hybrid couplers. A generalization of the simple Butler power divider using 3 dB hybrids may be used by employing variable phase‐shift networks between two 2
n
‐port Butler ones. The chapter establishes the possibility of realizing 3 dB hybrids with in‐phase or out‐of phase instead of in‐phase quadrature output signals by imposing a single symmetry plane on a four‐port network.