Approach to development of calculation methods of passive microstrip devices with symmetric structure based on the input impedances of partial schemes received by use of even-odd excitation of symmetric multiport are offered in the work. The expressions relating the input impedances of partial schemes of the transforming four-pole circuit and the directional four-port circuit with their scattering parameters are given. Features of usage of input impedances method for the design of different microstrip devices, including those on the basis of coupled line segments are considered.