Multi-input multiple-output (MIMO) techniques have been used in digital communications and hard-target radar applications to enhance the performance over single antenna (channel) in the last decade. In MIMO radar, the techniques improve the performance of multi-receiver array by using more than one spatially separated transmitter. We have successfully applied this concept at the Jicamarca Radio Observatory to improve the aperture synthesis radar imaging observations of equatorial electrojet irregularities. Given the transmitting modularity of Jicamarca, the implementation was straightforward, increasing the effective number of receiving modules, i.e., enhancing the visbility plane by adding one additional transmitter. In this work we plan to present preliminary results from experiments conducted at the Middle Atmosphere Alomar Radar System (MAARSY) in northern Norway. Previous aperture synthesis radar imaging experiments at MAARSY were conducted with 15 receiving antennas within MAARSY's ~100 m diameter array. Our MIMO experiments use three different anemones on transmission which implements time diversity. This configuration allow us to: (1) increase the number of effective receiver from 15 to 45 and (2) increase the effective diameter from ~100 m to ~150 m. The improved radar images are shown and discussed for the observations of Polar mesospheric summer echoes.