In order to improve the efficiency of BURST imaging, a new phase-modulation scheme of the DANTE-type RF excitation is proposed. It is shown that analytical optimization of the phase-modulation scheme with optimal SNR can be found for an arbitrary number N of subpulses in the RF excitation. Both theory and experiment indicate a maximum attainable gain in efficiency of the square root of N, compared to nonmodulated (constant-phase) excitation schemes.