this phenomina is simple you can easily understand it from Anteena theory and design by C.A balanis, and keep one thing in mind it is possible with anteena arrays only at least two anteenas, because beam shape depends on anteena fundamental radiation pattern in to array factor, if you are using dipole its fundamental radiation pattern is like 8 (depends on dipole placement) and now you can change it in to many shapes by using array of dipoles, by multiplying it with array factor, also you can check the effect in HFSS using array setup,