FDTD analysis of site free space VSWR in test site used for disturbance measurement above 1 GHz

The calculation of the site free space voltage standing wave ratio (S_VSWR) is important in designing the measurement facilities used above 1 GHz. In this study, the relations between the area of the absorbers on the ground plane and the S_VSWR were analysed using the FDTD method. The space, including the transmitting antenna, the receiving antenna, and the absorbers, were modelled using cells. The absorber constructed with foamed ferrite, ferrite tile, and wood was also modelled using cells. The calculation values almost agree with the measurement values, and the deviation between the calculation values using the FDTD method and the measurement values was smaller than the deviation between the calculation values using the ray trace method and the measurement values. The results suggests that the length similar to the distance between antennas is needed to acquire results similar to where absorbers are arranged over the entire ground plane (FAR), and that a width of 1.2 m also was needed to acquire the results similar to FAR.