Analysis and synthesis of asymmetric coupled lines in a homogeneous dielectric medium

Annotation: Asymmetric coupled lines with homogeneous dielectrics are studied, which are the basis for constructing of a transforming directional coupler with a weak coupling, a quadrature coupler divider with a double impedance transformation, as well as a 1:4 impedance transformer. Structures with weak and strong asymmetry, options for connecting matched loads, as well as conditions of physical implementation are considered. The formulas for calculating of the lines parameters, accompanied by geometric interpretation, are presented. Geometric ap- proach allows us to speed up and make visual analysis and synthesis. For the three test structures, frequency dependencies are given, as well as design parameters, including per-unitlength ones and modal ones. The presented formulas are implemented in the «AsymH» computer program.

Keywords: asymmetric coupled lines, homogeneous dielectric, per-unit-length parameters, per-unit-length capacitances, per-unit-length inductances, modal parameters, characteristic impedance, coupling coefficient, symmetry coefficient