5G and mm-waves is bringing exciting times to the RF industry. Never before has a generational change in the radio access technology caused such large changes in the architecture of radio base stations. The changes are driven by the introduction of beamforming and mm-waves. Mm-wave technology is nothing new, we have been using them since the 90s for point-to-point radio links. What is new is that we now want to pack 10 to 100 such mm-wave radios into a single active antenna array. To design and build such systems is a truly challenging engineering problem – tightly packed, power hungry signal chains. To make matters worse the systems should be designed for commercial customers that are not willing to pay for performance as defence customers. In this talk we will highlight and discuss the main challenges facing the front-end electronics in mm-wave active array systems for 5G base stations.