Space-time transmission diversity schemes have been known to provide considerable spectral efficiency as compared to other prevalent schemes. Space-time codes are also essential to exploit the full potential in a multiple antenna system. We propose a new blind signal detection of a user in a multiple user case where each of the users has multiple antennas. The transmission scheme employs space-time block coded symbols. The channel used for the simulations is a time varying channel based upon the classical model, which incorporates Doppler spreading, Rayleigh fading and multipath propagation with exponential delay. The blind detection scheme is based on constrained minimum output energy based detector at each of the receiver antennas.