Phase Property of Central-Symmetric Four-Ports Applied to Quadrature Directional Coupler Design in Asymmetric Coupled-Line Technology

Properties of ideally matched lossless four-port networks having central symmetry have been investigated. It has been shown that such networks feature ideal quadrature differential phase characteristics. It is shown that this unique property can be utilized for phase improvement of asymmetric coupled-line directional couplers. The presented theoretical investigation has been proven by measurements of two different directional couplers with a central symmetry designed in technology of multilayer asymmetric coupled lines.