This book is designed for both the scientific audience, research and development engineers and the university students. The fundamentals of radio frequency antenna beam forming is explained in this book. The principles of beam focusing and beam steering in near field and far field are visualized with 2D and 3D simulations and compared with measurement results. Besides linear and planar antenna arrays, also conformal arrays, i.e. concave and convex antenna arrays, suitable for certain applications, are investigated and presented. Also related applications of radio frequency beam forming like open loop and closed loop large scale antenna arrays or massive MIMO, which is one of the break-through technologies for 5G and future 6G and involves an extremely large number of antenna elements for the multi-user beam forming, as well as thinned antenna arrays with electrically large distances between the antenna elements are discussed.