Improvement of the formalism for calculating coupled microstrip lines - Application to the study of filters

A study of the use of microstrip filters in an inhomogeneous propagation medium shows that the proper and mutual influence coefficients of coupled microstrip lines vary linearly with respect to the dielectric constant of the medium. The formalism for determining the characteristics of the studied microstrip structures is simplified by use of the eigenvalues of the matrix formed of proper and mutual influence coefficients. The results are considered with reference to vectors representing the currents and with respect to the characteristic voltages of each propagation mode.