An RF model of an OpenMETA component comprises three-dimensional geometric shapes associated with materials of different electromagnetic properties. The OpenMETA tools currently support models that are in the CSXCAD format supported by the OpenEMS simulator. OpenEMS uses a finite-difference time-domain (FDTD) approach, where the problem space is first discretized along a rectilinear grid, then the electric (E) and magnetic (H) fields are cyclically updated in each timestep, for each grid point, using a finite-difference approach. As the direct simulation output is the time-domain evolution of the fields, frequency-domain characteristics of the model are deduced from the Fourier-transformed response to an adequately constructed excitation signal. In the context of the Ara module development, OpenEMS allows us to evaluate antenna performance (Zin, S11, directivity, etc.) and estimate the maximum SAR prior to production and FCC regulatory testing.