This paper examines the distinctive feature of studying the direct interaction between high power amplifiers located at the vicinity of the radiating elements without the use of isolators. In that case, the coupling effect between antennas, which leads to output impedance mismatching and degradation of the radiation pattern, will be described. Alongside, two methods have been developed to address this major drawback with some experimental results to validate the theoretical approach. An active antenna prototype including power amplifiers has been manufactured to validate a first approach of active antenna joint simulation, taking into account all the mentioned effects.