Optimal Power Splitting of Wireless Information and Power Transmission Using a Novel Dual-Channel Rectenna

Traditionally, the signal power is divided equally between dual functions in wireless information and power transmission (WIPT), which, intuitively, is not an optimal solution since the power sensitivities for communication and charging node pose different constraints for signals. To address this challenge, a two-channel rectenna with an asymmetrical coupler feeding network (ACFN) has been proposed for WIPT under the power-splitting and time-sharing (PS and TS) schemes. The proposed two-port rectenna consists of a receiving antenna integrated with ACFN where one output port is connected to a rectifying circuit, whereas the other is used for information recovery. Different from the conventional PS scheme with equal division, the proposed rectenna can adjust ratios of power at two outputs. That is, routing high power to the radio frequency (RF)-dc port, and transferring low power but of a sufficient signal-to-noise-ratio (SNR) to the port being used for signal demodulation/decoding. As a result, the simulated/measured maximum RF-dc conversion efficiency of the rectenna can reach up to 73.9%/70.4% for quadrature phase shift keying (QPSK) modulated signals and 63.9%/60.7% for continuous wave (CW) signals. In addition, good isolation between the two output ports ensures low interference against information decoding.

I. Introduction

Recently, an increasing number of low-power, long-range, and medium-rate wireless communication devices and networks (e.g., LoRaWAN, NB-Internet of Things (IoT), and Sigfox) have been emerged rapidly for applications on the IoT and wireless sensor networks. The use of wires and batteries to power such massive numbers of small devices and sensors becomes inconvenient and raise environmental concerns for battery fabrication and disposal. To enable maintenance-free and power autonomous devices, wireless power transmission (WPT) becomes a promising alternative solution. The WPT technologies can be categorized as inductive coupling, magnetic resonant coupling, and microwave power transmission (MPT). Among them, the microwave power transfer over a long distance (up to kilometers) can be regarded as a potential means of powering sensors with low/medium-energy consumption. Rectenna, which harvests ambient radio frequency (RF) energy and then converts it into useful dc power, is an important component in MPT systems [1].