Microwave Wireless Power Transmission Research Articles

On Design and Verification of an Efficient Microwave Wireless Power Transmission System

We report on the theoretical design and experimental verification of a high efficiency microwave wireless power transmission (MWPT) system operating in the Fresnel region. To achieve high conversion efficiency over a transmit distance of 11 meters, the transmit reflector antenna was optimized to locate the focal point at 11 m. The size of the receive antenna was decided by calculating the field distribution and the received power at different positions in the receive antenna aperture. Furthermore, an accurate model of the diode is presented, which was imported into the ADS software for high-precision rectifying circuit design. As a result, an overall DC-DC conversion efficiency of 20% was achieved, as measured in an anechoic chamber at a given distance of 11 m. The experimental results validated the proposed method.

Low complexity on-board vector calibration network for optimal microwave wireless power transmission and enhanced RF-to-DC conversion efficiency

A low complexity on-board vector calibration network for optimal microwave wireless power transmission (MWPT) efficiency is proposed in this work. The proposed technique is based on sequentially tracking the minimum power level of two antenna elements in an array for both phase and amplitude error discrimination. Unlike conventional vector calibration networks based on a down-conversion topology, the proposed architecture can perform vector calibration by only monitoring the magnitude of each antenna element. Thus, high system efficiency can be achieved by reducing hardware costs and eliminating any unnecessary power consumption by extra active devices. Further, phase and amplitude imbalances between antenna elements in an array can be accurately captured with higher precision compared to the conventional rotating-element electric-field vector (REV) method. The proposed technique achieved higher resolutions for both amplitude and phase error detection than REV, which suffers from low resolution near the maximum or minimum field crests. To verify the MWPT efficiency improvement based on the proposed calibration network, a 1 × 4 phased array MWPT system was fabricated and tested at 5.8 GHz with a reference rectenna. With the calibrated power transmission, the total RF-DC conversion efficiencies at ± 45° beamforming angles were improved by up to a maximum of 138.79%.

Dual‐Function Microwave Devices Based on Metamaterials

AbstractMicrowave detectors play a crucial role in modern technological applications, but traditional detectors suffer from limited functionality, limited detection accuracy, and difficulties in large‐scale deployment. This study proposes a dual‐function microwave detector based on metamaterials, capable of simultaneously measuring microwave power and polarization angle. The detector consists of a metal disc with 12 concave grooves, a dielectric layer, a metal reflector, and a resistive network. The designed detector achieves efficient absorption of 93.54% of microwave energy, with 75.4% dissipated in the resistive component and converted into heat. By detecting the temperature using a thermocouple thermometer, the incoming wave power can be determined, and by discriminating between different resistive temperatures, the polarization angle of the incoming wave can be identified. Simulation and experimental results demonstrate the outstanding detection efficiency and stability of this detector. It exhibits a linear response to different incident power densities and polarization angles, showing potential application value in the field of microwave wireless power transmission.

Hybrid Beamfocusing Architecture and Algorithm for Microwave Wireless Power Transmission Systems

Hybrid Beamfocusing Architecture and Algorithm for Microwave Wireless Power Transmission Systems

A Novel Multi-objective Synchronous Optimal Subarray Partition Method for Transmitting Array in Microwave Wireless Power Transmission

A Novel Multi-objective Synchronous Optimal Subarray Partition Method for Transmitting Array in Microwave Wireless Power Transmission

A Comprehensive Survey on Transmitting Antenna Systems With Synthesized Beams for Microwave Wireless Power Transmission

A Comprehensive Survey on Transmitting Antenna Systems With Synthesized Beams for Microwave Wireless Power Transmission

Gain-enhanced triple-band rectifier-integrated antenna for microwave wireless power transmission

Abstract This paper proposes a triple-band fractal slot antenna with enhanced gain operating at frequencies of 2.7, 3.5, and 4.8 GHz for microwave wireless power transmission. The antenna achieved more than 3 dB gain by preserving the symmetrical defected reflector structure behind it at a length of 0.54λ/4, where λ is the wavelength in free space at 2.7 GHz. A 50 Ω micro-strip line coupled at 66 mm length helps feed the triple band slot antenna. The purpose of a triple-band rectifier circuit with an impedance network is to convert the radio frequency (RF) signal into direct current. The measurements reveal that the antenna’s enhanced gain is 8.8 dB, and the rectifier’s highest RF signal to direct current conversion efficiency is 74.3%. For the combined configuration unit of measure, the antenna is assimilated into the rectifier via back-to-back 50 Ω Sub Miniature Version A (SMA) connectors. The highest recorded efficiency of 49.67% was obtained for the rectenna at optimum values of 1 kΩ resistive load and −5 dBm power input. It has been revealed that the rectifier-integrated antenna presented is effective for low-input RF energy capture and power transmission.

The X-band medium distance microwave wireless power transmission system based on multiplayer rectifier diode

The X-band medium distance microwave wireless power transmission (MWPT) system based on multilayer rectifier diode design is demonstrated in this paper. In order to pursuit highest rectification efficiency, the harmonic suppression rectifying circuit is proposed, which can acquire more than 60% rectification efficiency at the working frequency of 10 GHz. For the sake of longer distance, the Cassegrain antenna with an aperture of 1.6 m and the receiving planar array antenna with an area of 2 m × 2 m for the novel applications are designed. In the interest of improving the effective receiving area, the microwave rectifying antenna adopts the layered design of the receiving array antenna and the microwave rectifying circuit. Finally, this X-band medium distance MWPT system based on multilayer rectifier diode can achieve 400 W DC power with 10% RF-DC conversion efficiency for the distance of 70 m. The MWPT system can been applied in medium to long distance MWPT system, such as charging of various sensors, wireless power supplying and so on.

An S-Band Compact Meander-Line Dual-Polarized Rectenna Array Design and Application Demonstration

This paper presents a compact, dual-polarized rectenna array operating at 2.45 GHz and demonstrates its use in a microwave wireless power transmission (MWPT) system. The MWPT system comprises a compact voltage-controlled oscillator (VCO), a power amplifier (PA), and the dual-polarized rectenna array. The VCO and PA together form a transmitter that delivers an output power of 1 W at 2.45 GHz. The transmitter’s DC power port features a universal type-C interface, which facilitates its use in daily life. We designed a meander-line dipole rectenna that eliminates the matching network between the antenna and diode. The meander-line structure improves the rectenna’s impedance and reduces its size. The measured maximum efficiency of the rectenna is 62.5% at −2 dBm. DC power combining is applied to the rectenna array to achieve dual polarization and voltage boosting simultaneously. The proposed rectenna array is integrated into a commercial digital thermometer. The digital thermometer was powered by the proposed MWPT system, demonstrating its bright prospects for MWPT applications.

Optimisation method for efficiently determining feed parameters of phased array antenna in microwave wireless power transmission

AbstractIn the microwave wireless power transmission (MWPT) system, to improve the beam collection efficiency (BCE) and decrease the impact of microwave on the ecological environment outside the receiving area, it is necessary to optimise the beam pattern of transmitting antenna which includes accurate beam pointing and low sidelobe level. Furthermore, when the target is moving, the synthesised beams are required to track the target within a certain range. To track the target quickly and reduce the influence of the beam pattern's distortion on the BCE, this article proposes a time‐saving and effective method to optimise the feed parameters of the phased array antenna (PAA). This method draws on the ideas of Auto‐Encoder network, and uses multi‐layer perceptron to establish a mapping relationship between the desired beam pattern and the feed parameters of PAA. At the same time, to consider the coupling effect between antenna elements, the Eigen‐driven analysis method is adopted to form the actual beam pattern without calling the full wave simulation results. To make the actual beam pattern as close to the desired beam pattern as possible, Adaptive moment estimation algorithm is used to realise the error back propagation. After several iterations, when the error is minimised, the optimal feed parameters can be obtained. The advantage of the proposed method is that speedy focussing and high efficient energy transmission can be realised for the targets in a certain position. A set of examples and corresponding comparative analysis are presented to demonstrate the performances and superiority of the proposed method in MWPT system.

Polarization-Tilt-Insensitive Microwave Wireless Power Transmission by Orthogonal Excitations

Polarization misalignment between transmitting (TX) and receiving (RX) antennas inevitably leads to severe degradation of wireless link. To guarantee an aligned polarization propagation, TX and RX dual-linearly polarized (DLP) antennas are employed. When two orthogonal signals are excited at horizontally polarized (HP) and vertically polarized (VP) ports of the TX DLP antenna, polarization-tilt-insensitive microwave power transmission can be achieved at both HP and VP ports of RX antenna, which allows maximum RF-to-dc rectification by two parallelly dc-combined rectifiers. Selected distances (50 and 100 cm) and polarization tilts ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi $</tex-math> </inline-formula> varies from 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> to 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \varphi = 30^{\circ})$</tex-math> </inline-formula> are carried out for experimental measurements, which along with theoretical analysis validates its effectiveness of such polarization-tilt-insensitive microwave power transmission by orthogonal excitations.

An Irregular Tiled Array Technique for Microwave Wireless Power Transmission

An irregular tiled array technique with the maximization of beam collection efficiency (BCE) for microwave wireless power transmission (WPT) is addressed in this paper, where the radiating elements are irregularly partitioned into multiple subarrays for reducing the number of radio frequency (RF) chain. The system architectures of WPT based on irregular tiled arrays are analyzed for the exhibition of its low-cost advantages. To achieve a good trade-off between the manufacturing cost and beampattern, a mixed-integer optimization problem (MIOP) accounting for the maximization of BCE satisfying the subarray tiling configuration, scanning direction and peak sidelobe level (SLL) constraints is established. By equivalently reformulating the beampattern, the MIOP in terms of subarray tiling configuration and subarray excitations is decoupled, and a two-stage solution method can be implemented. Firstly, resort to ‘generalized BCE’, the binary quadratic optimization problem (BQOP) for maximizing the BCE at considered scanning angles while guaranteeing the full aperture coverage is reduced to a binary second-order cone optimization problem. After the subarray tiling configuration is determined, the non-convex Rayleigh entropy maximization problem at a given scanning angle with respect to subarray complex excitations while satisfying peak SLL constraint is globally solved by using iterative convex approximation algorithm. Owing to the high efficiency of convex optimization, the BCE is able to monotonically increase to a stable value. Several numerical results with different array size and subarray shapes are provided to assess the effectiveness of the proposed method by comparing to the competitive counterparts in the open literatures.

Planar Array Subarray Division Method in Microwave Wireless Power Transmission Based on PSO&amp;K-Means Algorithm

Planar Array Subarray Division Method in Microwave Wireless Power Transmission Based on PSO&amp;K-Means Algorithm

A 5.8 GHz π-Stub Decoupling Network for Receiving Antenna Arrays in Microwave Wireless Power Transmission

In this paper, a 5.8 GHz π-stub decoupling network is proposed to improve the performance of a receiving antenna array (RAA) in microwave wireless power transmission (MWPT) systems. A set of general design formulas was derived for determining the electric parameters of the required π-stubs. To validate the new technique, a π-stub decoupling network was combined with RAAs. The simulated and measured results show that the performance of the RAA is greatly improved by loading the π-stub decoupling network. In addition, a miniaturized MWPT system was built. System-level measurements indicate that the novel decoupling network enhances the receiving power of the RAA by up to 36.4%. An extended application also shows the scalability and effectiveness of the network, implying its huge potential in large-scale receiving arrays.

A 5.8-GHz Rectifier Using Diode-Connected MESFET for Space Solar Power Satellite System

To improve the power handling capability at ground stations of a 5.8-GHz solar space power satellite using microwave power transmission, a power charge-pump meta-semiconductor field-effect transistor (MESFET)-based rectifier is presented in this article. Unlike conventional microwave Schottky diodes, diode-connected MESFETs, whose nonlinear characteristics help them to have a unique current–voltage (I-V) curve that overcomes the limitations of a Schottky diode. Thus, the maximum input power of the proposed rectifier is extended up to 251.2 mW by replacing a Schottky diode with a diode-connected MESFET. Additionally, a class F harmonic processing network is introduced to control the voltage and current waveform at the load of the rectifier. Consequently, the RF-dc conversion efficiency is increased since the power dissipation is limited at the junction resistance of both the drain and the source of the MESFET. Owing to the abnormal characteristics of the diode-connected MESFET, the measured conversion efficiency of our rectifier is approximately 73.2% at 126 mW, and the input power range for rectifier efficiency higher than 50% is between 16 and 224 mW. The proposed rectifier for the space solar power satellite application is demonstrated and verified using a microwave wireless power transmission system.

An Impedance Matcher for Microwave Rectifier to Broaden Load Range

In this letter, a novel impedance matcher (IM) is designed based on Zeta converter to overcome the shortcomings of other impedance matching methods and improve the load range in low resistances. System-level verification demonstrates that the novel IM has a potential application value for microwave wireless power transmission (MWPT) system. Measurement results show the maximum power conversion efficiency (PCE) of the novel rectifier with IM can reach 73% when the input power is 32 dBm. In addition, the proposed rectifier circuit with IM can operate with above 60% overall efficiency when the load varies from 0.01 to 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> (1:1000) as input power of 32 dBm. Compared with that without IM, the application of IM can increase the load range by at least 1100% when the rectifier efficiency is >50.7%. The measurement results demonstrate that the rectifier circuit has a better performance when connected to the novel IM.

Development of High-Power Charge Pump Rectifier for Microwave Wireless Power Transmission

This study theoretically and experimentally indicates that a charge pump rectifier for low-power rectifiers such as RF-ID can be applied to high-power rectifiers and can attain the same level of RF-dc conversion efficiency and twice as high power rectification as the single-shunt rectifiers. A high-power rectifier is primarily a single-shunt rectifier, and a charge pump rectifier that applies twice the output voltage is used in low-power applications such as RF-ID. We aim to enhance the power of charge pump rectifiers by focusing on their characteristics. A fabricated 5.8 GHz charge pump rectifier achieved an RF-dc conversion efficiency of 70.8% at an input power of 8.0 W and a load resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$150\,\Omega$</tex-math></inline-formula> . This result is also the highest efficiency for 39 dBm rectifiers in the 5.8 GHz band. Compared to a single-shunt rectifier with the same diode, the charge pump rectifier generated twice the input power and efficiency difference of 2.9% at the maximum input power. These results indicate that the charge pump rectifier has an advantage over the single-shunt rectifier in high-power rectifiers.

Synthesis of sparse square arrays with high beam collection efficiency under minimum element spacing constraints

AbstractThis letter presents a large spacing nonuniform distribution, uniform excitation sparse square array model to maximize beam collection efficiency (BCE) and minimize sidelobe level outside the collection area (CSL) of the transmitting antenna in microwave wireless power transmission (MWPT) systems. We improve the position update parameters in the dynamic weight particle swarm optimization (DWPSO) algorithm by adding multiobjective learning features (MODWPSO). We use MODWPSO to optimize the elements' positions to maximize BCE and minimize CSL and discuss the effect of the minimum element spacing value on BCE and CSL. By comparing the array performance with a typical array model, it can be concluded that the proposed large spacing sparse nonuniform distribution, uniform excitation square array model has higher BCE, lower CSL, and fewer costs.

A wideband monopole antenna with diplexer and rectifier for simultaneous energy harvesting and data communication

A wideband coplanar waveguide fed monopole antenna with diplexer and rectifier for microwave wireless power transmission and communication is proposed. The antenna is comprised of an asymmetric ground plane with an open stub, a rectangular monopole, and a square loop with a gap at the bottom. A microstrip line diplexer is implemented by using stepped impedance resonator slots to split the signal without extra matching circuits. A microwave rectifier based on the voltage doubler topology is designed for wireless power transmission. The prototypes are fabricated, measured, and compared with the simulated results. Measured results demonstrate that the −10 dB impedance bandwidth (1.42 GHz) of the antenna reaches 69.6% (1.33–2.75 GHz), the diplexer minimum insertion losses ( S 21 $$ \left|{S}_{21}\right| $$ , S 31 $$ \left|{S}_{31}\right| $$ ) are 2.13 dB, 3.27 dB at pass band frequencies, the output isolation ( S 23 $$ \left|{S}_{23}\right| $$ ) better than 20 dB from 1 to 3 GHz, and the peak RF to DC conversion efficiency of a rectifier is 56%. The integration of the proposed antenna, diplexer, and rectifier novel configuration is suitable for simultaneous wireless power transmission and communication applications.

Experimental and numerical investigations of the transmitting antenna in microwave wireless power transmission with forced air cooling system

To address the heat dissipation problem of the transmitting antenna in microwave power transmission system, an optimization design approach is proposed in this paper. Based on the characteristic analysis of the transmitting antenna, an accurate simulation analysis model of three-channel heat dissipation system is established using computational fluid dynamics simulations and experiments. The influences of the structural parameters of heat sink on the heat dissipation performance of the antenna under different indexes are analyzed using the orthogonal experimental design method, and the heat sink are optimized. The results show that the fin pitch of the heat sink is the main factor influencing the maximum temperature and the temperature standard deviation, while the fin height is the main factor affecting the average temperature. Compared with the original design, the optimized heat sink can significantly improve the heat dissipation performance of the transmitting antenna, and the maximum temperature, average temperature, and temperature standard deviation are reduced by 8 °C, 5.9 °C, and 2.1 °C, respectively. The transmitting antenna prototype test verifies the heat dissipation performance of the transmitting antenna with the optimized heat sink. Therefore, the presented approach is suitable for the optimization design of the heat dissipation system of array antennas. • A forced air cooling thermal management system for the transmitting antenna is designed. • The orthogonal design method is used to optimize the plate fin heat sink of the transmitting antenna. • Multiple factor analysis is performed for the forced air cooling system. • The optimized plate fin heat sink based on the orthogonal design method achieves good performance. • Experiments are conducted to verify the thermal performance of the forced air cooling thermal management system.