A study of the surface current distribution on the microwave transmission line using Green's function

A method for estimating the currents on the microwave transmission line is proposed. In this method, the substrate is divided into a wire-grid model. Then the magnetic near field strength above the microwave transmission line is calculated and measured. Based on the magnetic near field strength, the magnetic field integral equation is established by applying the Green's function and is used to estimate the currents flowing on the microwave transmission line. In this paper, the current distribution which is calculated by FDTD method with the interpolation (first order) and estimated current distribution by applying the Green's function on the microstrip line and the coplanar line is evaluated by using the calculated magnetic field components. As a result, a good agreement between both results is observed and the validity of this method is confirmed. Furthermore, the validity of the current estimation by measuring the magnetic near fields is confirmed by comparing the current obtained from the measured magnetic fields and the calculated magnetic fields. Comparing between the measured and calculated results, a good agreement is observed between both results on the strip line area. However, differences are also observed on the dielectric substrate area.