Optimum design of broadband coupled-line phase shifters incorporating impedance matching of source and load impedances

In this paper, the method of least squares is used to the optimum design of the modified coupled-line phase shifter, which used the dissipation effect and dispersion relations of the microstrip coupled lines in their microwave circuit models. An error function is constructed based on the even- and odd-mode analysis, impedance, transmission and scattering matrices of the phase shifter, which is a frequency of its geometrical dimensions, such a widths, gaps and lengths of strips. The design procedure also incorporates the specified wide band source and load impedances. The minimization algorithm is used as the combination of the genetic algorithm and conjugate gradient method. Several examples of the coupled-line phase shifters are designed for some specifications and their performance are checked by the HFSS full-wave packages.