Received Power-Based Channel Estimation for Energy Beamforming in Multiple-Antenna RF Energy Transfer System

Abstract

In this paper, we propose a channel estimation algorithm based on the received power measurements for the multi-antenna radio frequency (RF) energy transfer system. The energy beamforming is a key technology to resolve a low energy transfer efficiency problem of the RF energy transfer system, which is mainly caused by a free-space path loss. The channel gains between transmit and receive antennas should be estimated to use the energy beamforming technique. We propose a received power-based channel estimation scheme that can be implemented by means of a simple power meter at a receiver. In the proposed scheme, the receiver measures the received power of the RF signal and sends a feedback containing the received power measurements to the transmitter. We formulate a channel estimation problem, which is recast into a linear estimation problem by using complex vectorization. Then, this linear estimation problem is solved by the ordinary least squares method and the Kalman filter-based algorithm. We also propose a method to reduce the dimension of the estimation problem when there are a smaller number of receive antennas than transmit antennas.