A common theme in modern wireless communications is the use of multi-antenna techniques, such as beam-forming and spatial multiplexing in order to improve the cell capacity and throughput. A common problem encountered by customers today, is the inability to verify and visualize the signal at the RF antenna. This application note briefly summarizes multi-antenna techniques, before introducing the concept of beam-forming, its advantages and specific use within modern communications systems such as LTE. Multi-antenna beam-forming measurement challenges are discussed from an eNB base station test perspective, as well as the importance of calibration when testing the performance of a beam-forming transmission system.