Hi everyone, I’m working on a planar antenna design in CST, where the antenna is patterned on a 500 μm thick sapphire substrate with a gold ground plane underneath. I’m trying to perform characteristic mode analysis (CMA) to understand the supported modes and tune my design accordingly. However, when I try to run the simulation using the Integral Equation Solver, I get an error saying “Lossy materials are not supported for the characteristic mode analysis.” I changed the gold to PEC to avoid the loss issue, but the error still appears. I suspect the problem is with the sapphire substrate, but I’m not sure how to handle it—should I remove it completely or approximate it somehow? I’m looking for guidance on the right way to set up CMA for a structure like this in CST, especially how to deal with the substrate while still getting accurate modal results. Please let me know how to solve the issue
