  The energy spectrum, spectral density and phase diagrams have been obtained
for two-sublattice hard-core boson model in frames of random phase
approximation approach. Reconstruction of boson spectrum at the change of
temperature, chemical potential and energy difference between local positions
in sublattices is studied. The phase diagrams illustrating the regions of
existence of a normal phase which can be close to Mott-insulator (MI) or
charge-density (CDW) phases as well as the phase with the Bose-Einstein
condensate (SF phase) are built.
