  Energy efficiency (EE) is an important aspect of satellite communications.
Different with the existing algorithms that typically use the first-order
Taylor lower bound approximation to convert non-convex EE maximization (EEM)
problems into convex ones, in this letter a two-step quadratic transformation
method is presented. In the first step, the fractional form of the achievable
rate over the total power consumption is converted into a non-fractional form
based on quadratic transformation. In the second step, the fractional form of
the signal power over the interference-and-noise power is further converted
into a non-fractional form, still based on quadratic transformation. After the
two-step quadratic transformation, the original EEM problem is converted into
an equivalent convex one. Then an alternating optimization algorithm is
presented to solve it by iteratively performing two stages until a stop
condition is satisfied. Simulation results show that the presented algorithm
can fast converge and its performance is better than that of the sequential
convex approximation algorithm and the multibeam interference mitigation
algorithm.
