Newly developed MMIC-processes (Monolithic Microwave Integrated Circuit) based on silicon and III-V compound semiconductors, have opened the possibility of realizing integrated circuits, with operating frequencies up to and above 300 GHz. By exploring these technologies, it would be possible to realize low-cost systems in this frequency range with a complexity that can be found only at lower frequencies. Examples of typical applications are wireless communication systems with significantly higher data rate compared to existing commercial products. Such systems are, as an example, needed in the near future for the mobile internet access service providers in order to comply with the customer needs for increased data rate in smartphones, iPads, Laptops etc. Such communication links can for instance be used for the backhaul network of base stations, where data from base stations are transferred to the fiber network.