Hi, wave port is a perfect definition of a port which software calculates field distribution on it and impedance will be calculated too. But if there be no possibility to define the port inside the simulation volume, it is not the best solution but the only solution to define lumped port. Opposing the wave port, lumped port doesnt calculate the field distribution and only excites a voltage at the lumped port location and calculates current and extracts structure specifications. Thats why we can attribute an impedance to it.