Abstract
A high-efficiency microwave power transmission (MPT) system based on an inverted class F ( $\text{F}^{-1 }$ ) rectifier for microwave wireless charging applications is presented in this paper. A left-hand circular polarization (LHCP) transmitting antenna (Tx) is designed based on a modified sequential phase rotation (SPR) divider integrated with a $2\times 2$ array. The proposed Tx exhibits compact size with LHCP maximum gain of 11.85 dBi at 5.8 GHz. Furthermore, the receiver is composed of an LHCP receiving antenna (Rx) and a microwave $\text{F}^{-1}$ rectifier. To realize the power radiated region of the Tx, an Rx with a wide beamwidth for minimizing distance loss is proposed, which has a 3-dB axial ratio (AR) beamwidth of 165.55° and 175.17° in the $x - z$ and $y - z$ planes, respectively. In addition, to improve the RF to DC conversion efficiency ( $\eta $ ), the class $\text{F}^{-1}$ harmonic processing network is utilized at the load of the rectifier that can process the voltage and current waveforms without using a DC pass filter. The proposed $\text{F}^{-1}$ rectifier circuit occupies a compact area of $15.3\times12.7$ mm2, and it exhibits an average $\eta $ of 50% for the input power range from 4 to 20 dBm with a peak efficiency of 77.9% at 18 dBm. Overall, the experimental results show that our proposed system achieves a maximum power transmission efficiency (PTE) of 8.8% for wirelessly charging low-power multiple devices at a distance of 60–200 mm.
Highlights
I N recent years, advances in science and technology have enabled wireless power transmission (WPT) applications to be deployed in the industrial, scientific, and medical (ISM) fields such as smart-watch strap chargings [1], contactless battery chargers for cellular phones [2]–[4], and consumer electronics [5]
We propose and investigate a complete longdistance microwave power transmission (MPT) system for charging multiple devices, as illustrated in Fig. 1. which consists of an sequential phase rotation (SPR) ring antenna and a class F−1 rectenna
Theoretical analysis shows that the proposed Tx can achieve a high concentration of energy toward the Rx antenna
Summary
I N recent years, advances in science and technology have enabled wireless power transmission (WPT) applications to be deployed in the industrial, scientific, and medical (ISM) fields such as smart-watch strap chargings [1], contactless battery chargers for cellular phones [2]–[4], and consumer electronics [5]. Several methods are used to solve the misalignment problem and increase the transmission efficiency of the WPT system, such as using a gain-boosting array technique [12], dual-layer printed circuit board (PCB) metamaterial [13], omnidirectional magnetic field based on cubic Tx [14], butterfly shape Tx [15], and multiple transmitters [16], [17] These works achieved several good characteristics for improving the coupling efficiency, most of these structures are relatively complicated and sizeable.
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