  This paper presents a new approach to efficiently maximizing the energy
efficiency (EE) of hybrid arrays under a practical setting of non-ideal power
amplifiers (PAs) and non-negligible circuit power, where coherent and
non-coherent beamforming are considered. As a key contribution, we reveal that
a bursty transmission mode can be energy-efficient to achieve steady
transmissions of a data stream under the practical setting. This is
distinctively different from existing studies under ideal circuits and PAs,
where continuous transmissions are the most energy-efficient. Another important
contribution is that the optimal transmit duration and powers are identified to
balance energy consumptions in the non-ideal circuits and PAs, and maximize the
EE. This is achieved by establishing the most energy-efficient structure of
transmit powers, given a transmit duration, and correspondingly partitioning
the non-convex feasible region of the transmit duration into segments with
self-contained convexity or concavity. Evident from simulations, significant EE
gains of the proposed approach are demonstrated through comparisons with the
state of the art, and the superiority of the bursty transmission mode is
confirmed especially under low data rate demands.
