With improvements in hardware of antenna receivers, fully digital arrays have been made possible to use in real time systems. These systems have a greater complexity, with the advantage of more dynamic system design since the use of the communication system can be changed with only a software change. Construction of a system capable of bidirectional communication on the same frequency and at the same time, is possible with a fully digital array if the coupling between the antenna elements are known. The good thing about the system is that all components for measuring this coupling already are included in the fully digital array. A signal generator and a coherent multichannel receiver can be used to create a VNA, completely by software. This can be used to measures the coupling coefficients of the antenna elements. In this thesis the working principle of the the software defined VNA is proven, a testing environment for a antenna array is described andadjustments for real hardware are used to create a result which can be strongly correlated to measurements of a lab grade VNA used as reference.