  The low efficiency of far-field wireless power transfer (WPT) limits the
fundamental rate-energy (R-E) performance trade-off of the simultaneous
wireless information and power transfer (SWIPT) system. To address this
challenge, we propose in this letter a new SWIPT system aided by the emerging
intelligent reflecting surface (IRS) technology. By leveraging massive low-cost
passive elements that are able to reflect the signals with adjustable phase
shifts, IRS achieve a high passive beamforming gain, which is appealing for
drastically enhancing the WPT efficiency and thereby the R-E trade-off of SWIPT
systems. We consider an IRS being deployed to assist a multi-antenna access
point (AP) to serve multiple information decoding receivers (IDRs) and energy
harvesting receivers (EHRs). We aim to maximize the weighted sum-power received
by EHRs via jointly optimizing the transmit precoders at the AP and reflect
phase shifts at the IRS, subject to the individual
signal-to-interference-plus-noise ratio (SINR) constraints for IDRs. Since this
problem is non-convex, we propose efficient algorithms to obtain suboptimal
solutions for it. In particular, we prove that it is sufficient to send
information signals only at the AP to serve both IDRs and EHRs regardless of
their channel realizations. Moreover, simulation results show significant
performance gains achieved by our proposed designs over benchmark schemes.
