Modern transmitter architectures make use of multi-input multi-output (MIMO) techniques, employing a high number of RF power amplifiers (PAs) to excite an antenna array. The array elements are often coupled, creating an excitation at the output of the PAs, which is dependent on the outputs of the other elements. Therefore, in this system, the nonlinear behavior of each PA cannot be fully described solely as a function of its input. In order to characterize a device that will operate in this arrangement, it is important to develop setups that are capable of exciting the PA at the input and output, synchronously at the RF carrier (phase control) and envelope (delay control) levels, with correlated or independent amplitude and phase modulations. In this paper we propose a setup for this type of characterization and show how it can be calibrated to correct the frequency response of the observation paths and the excitation paths in a simple way using broadband modulated signals, covering the full measurement bandwidth.