Comments on "Numerical errors in the computation of impedances by FDTD method and ways to eliminate them" [with reply]

For original paper, see Fang and Xue, ibid., vol. 5, no. 1, pp. 6-8 (Jan. 1995). The original paper presents a new formula for the calculation of the characteristic impedance of transmission lines, Z/sub 0/, using the FDTD method. This formula eliminates the numerical errors due to the offset of voltages and currents in space and time. The commenters recalculate the two examples given and confirm the presented results. However, they point out that using the exact formula for the characteristic impedance yields a value of Z/sub 0/ = 50.2 /spl Omega/ for the stripline investigated. In response to the comments, the original authors analyze the variation of the numerical error with respect to the space step.<>