In this report a numerical solution for the dual band transmit-array challegenge proposed for the WORKSHOP EM-ISAE 2018 (test case nº 4) is presented. The numerical results are compared with the measurements of the corresponding prototype (see Figure 1). More details about the design and fabrication processes of the dual band TA can be found in [1]. To perform the corresponding full-wave simulations was quite challenging, mainly due to the large volume occupied by the antenna (comprising the feed and lens) and the fine subwavelength details of the unit cells that populate the TA. In fact, we did not had at that time sufficient memory to perform the full-wave simulation of the complete antenna (feed+lens). In this workshop we detailed the developed approach used to conduct the full-wave analysis of the TA within our available computational resources.