Nothing can grow exponentially forever, but wireless communication still seems to do so. Especially video and Cloud content increasingly produces huge wireless data streams to mobile phones and other multi-media devices, while new wireless applications come up, e.g. for the “Internet of Things”. All these wireless devices compete in using the scarce radio spectrum, and mutual interference is rapidly becoming a bottleneck, as 2.4GHz WiFi users already begin to experience. For radio transmitters, the target is to focus the transmit beam(s) in the most useful direction to reduce the “interference footprint”, increase the data capacity per area, and increase power efficiency.