Comments on 'The Far Zone Scattering Calculation of Frequency-Dependent Materials Objects Using TLM Method'

摘要

In [1], the authors state, as if it were an evident fact, that the transmission line matrix (TLM) method implementation for dispersive media using the three-dimensional hybrid symmetrical condensed node (HSCN) node requires the introduction of voltage sources through ports 16-18. This is only one of the possible approaches that has been already presented in [2] and [3] that the authors do not mention. There are also other approaches, as in [4] and [5]. In fact, the addition of current sources in the TLM method was already proposed by Scaramuzza et al. [6], the voltage sources having been first proposed by our work [2]. The authors write, in [1, eq. (1)] the updating equation for the sources as if it were a well-known topic in TLM theory, with no demonstration nor reference. In fact, [1, eq. (1)] is exactly the same equation as [3, eq. (11)], and its deduction is a wide part of that paper. Furthermore, the authors do not mention that [1, eq. (1)] is valid only when constant convolution is employed; other existing alternatives such as trapezoidal convolution are also presented in [3]. Moreover, the admittance Y in [1, eq. (1)] is not the "admittance of the dispersive material" (that, of course, must be frequency dependent) but the normalized admittance of the permittivity stubs.