  Simultaneous wireless information and power transfer (SWIPT) is an appealing
research area because both information and energy can be delivered to wireless
devices simultaneously. In this paper, we propose a diplexer-based receiver
architecture that can utilizes both the doubling frequency and baseband signals
after the mixer. The baseband signals are used for information decoding and the
doubling frequency signals are converted to direct current for energy
harvesting. We analyze the signal in the receiver and find that the power of
the energy harvested is equal to that of information decoded. Therefore, the
diplexer can be used as a power splitter with a power splitting factor of 0.5.
Specifically, we consider a multiuser multi-input single-output (MISO) system,
in which each user is equipped with the newly proposed receiver. The problem is
formulated as an optimization problem that minimizes the total transmitted
power subject to some constraints on each user's quality of service and energy
harvesting demand. We show that the problem thus formulated is a non-convex
quadratically constrained quadratic program (QCQP), which can be solved by
semi-definite relaxation.
