Curve Fitting-Based Phase Optimization for Microwave Power Transfer

Abstract

Microwave power transfer provides power wirelessly by converting electromagnetic waves emitted by an antenna to DC power using a rectifying antenna (rectenna). We are developing a distributed cooperative power transfer system that intentionally generates constructive interference on a device by applying appropriate phase control to microwaves emitted from each antenna to improve the efficiency of the power supply. This paper proposes a novel phase optimization method to find the optimal phase that maximizes the received power of the device. The proposed method obtains the optimal phase by performing nonlinear curve regression based on the received signal strength indication (RSSI) feedback of the device. Experimental evaluations showed that the proposed method improved the stability of the supplied power and reduced the time of phase optimization in both feedback models.

Beamforming Algorithm Based on the Orthogonal Phase Bases With Trigonometric Estimation for Microwave Power Transfer Systems

“…Since simultaneous phase shifting for half of the Tx elements is performed, this technique has a relatively high Rx SNR, compared to the algorithms based on phase shifting of a single Tx element at a time or RSS variations as in Refs. [14]- [17] and [21]- [23]. Unlike Refs.…”

“…To reduce the number of measurements required for convergence, adjusting the step size of perturbation according to the magnitude variation of the RSS was proposed [16], [35]. The algorithm reported in [17] solves a nonlinear least square problem using Levenberg-Marquardt method. The received power after each iteration gradually approaches to the maximum RSS point from randomly produced samples.…”

“…Unlike Refs. [14]- [17] and [35], the proposed algorithm generates the 3N -2 beams with phases of 0 • , 90 • , and power-off states of other elements, so that if the received power levels of the multiple Rx's are determined, optimum phase sets for the multiple Rx's can be simultaneously obtained using a single beam sequence. Compared to the methods presented in Refs.…”

“…Because these devices require relatively low operating power, long-range wireless charging can be considered for convenience, rather than the conventional wired or short-range wireless charging methods. The MPT method has been studied for long-range wireless charging applications for these devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Since the MPT method uses electromagnetic wave for power transmission, adaptive beamforming using a phased array is generally adopted to increase the power transmission efficiency, and to track the Rx's.…”