Recent works have demonstrated the feasibility of microwave imaging using compressive techniques, exempting the use of active delay lines, phase shifters, or moving parts to achieve beamforming. With this method, waves are coded in a passive way by a compressive device to reduce the complexity of the transmitter and/or receiver chains of the telecommunication and radar systems requiring beamsteering. Such a technique is based on the exploitation of the frequency diversity, implying that a reduction of the compressive device's volume imposes a diminution of the number of driven antennas. In this paper, the improvement brought by simultaneous excitations of the compressive device is presented. Adapting a new mathematical formulation, it is shown that M inputs can send independent waveforms allowing the beamsteering of an N-elements antenna array, while maintaining N > M.