1. A multi-antenna wireless device comprising: a plurality of (N) receiver units operatively coupled to a plurality of antennas, one receiver unit for each set of at least one antenna from among the plurality of antennas, each receiver unit operable to process a respective input signal and provide an output signal, wherein N is a positive integer number; and a controller that selectively enables or disables respectively each of the N receiver units based at least in part on a current operating state and a current mode of operation of the wireless device, the current operating state is one of a subset of available operating states comprising an idle state, a sleep state, and a communication state, wherein the wireless device operates in the idle state, the sleep state, and the communication state at respective times, the current mode of operation is one of a subset of available modes of operation comprising single-input (SI) mode for reception of one input signal via one antenna of the plurality of antennas multiple-input (MI) mode for reception of multiple signals via multiple antennas of the plurality of antennas and a standby mode wherein all of the N receiver units are disabled, the wireless device operates in the SI mode, the MI mode and the standby mode at respective times, and wherein the available operating states and available modes of operation are respectively associated with respective different combinations of enabled receiver units of the plurality of (N) receiver units, wherein each of the respective different combinations of the enabled receiver units ranges from zero receiver units enabled up to N receiver units enabled.