Closed form expressions for microstrip line input impedance in quasi-dynamic approach

Quasi-dynamic closed expressions for calculation of the dispersion dependences of the microstrip line input impedance are proposed. These expressions provide high accuracy calculation of the input impedance on the initial section of the axis in the area of weak dispersion of the microstrip parameters and reproduce the tendency of change of dispersion curves with increasing frequency. For the analysis of the microstrip line, the impedance type integral equation was used which was composed by the use of quasi-dynamic Green´s function approximation.