  An intelligent reflecting surface (IRS) is invoked for enhancing the energy
harvesting performance of a simultaneous wireless information and power
transfer (SWIPT) aided system. Specifically, an IRS-assisted SWIPT system is
considered, where a multi-antenna aided base station (BS) communicates with
several multi-antenna assisted information receivers (IRs), while guaranteeing
the energy harvesting requirement of the energy receivers (ERs). To maximize
the weighted sum rate (WSR) of IRs, the transmit precoding (TPC) matrices of
the BS and passive phase shift matrix of the IRS should be jointly optimized.
To tackle this challenging optimization problem, we first adopt the classic
block coordinate descent (BCD) algorithm for decoupling the original
optimization problem into several subproblems and alternatively optimize the
TPC matrices and the phase shift matrix. For each subproblem, we provide a
low-complexity iterative algorithm, which is guaranteed to converge to the
Karush-Kuhn-Tucker (KKT) point of each subproblem. The BCD algorithm is
rigorously proved to converge to the KKT point of the original problem. We also
conceive a feasibility checking method to study its feasibility. Our extensive
simulation results confirm that employing IRSs in SWIPT beneficially enhances
the system performance and the proposed BCD algorithm converges rapidly, which
is appealing for practical applications.
