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The concept of long-range microwave power transmission (MPT) has been driven by the desire to remotely power satellites, drones, or some mobile facilities. The advantage of long-range MPT is power transmission over a long distance without the need to deploy a wired power network. However, the overall efficiency, robustness, directional radiation (DR), and so on are still issues that limit the application and further research. In this framework, the key challenges in designing transmitters, DR, and receivers that can guarantee high efficiency and precise tracking for long-range MPT have been acknowledged. Owing to the complexity, the design of the MPT systems remains an open research question. Focusing on the existing constraints, this article not only elaborates on the current major research topics and discusses the development trends but also reviews the design approaches proposed in the state of the art for long-range MPT. This power transmission mechanism shows essential meanings of application in daily life, and the current research status and development prospects for MPT are also presented in this article.

This article presents a novel resonant-linear hybrid converter for a radio frequency (RF) power amplifier (PA). The proposed topology consists of a push–pull resonant inverter and a voltage-controlled linear amplifier at the output port. The push–pull resonant inverter consists of two single-ended Class $\Phi 2$ inverters, and the voltage-controlled linear amplifier controls the output voltage to track the phase of the reference voltage for phase control of the output. Thus, the output voltage can be well controlled as a pure sinusoidal curve. A driving circuit is presented in this article to make the output current of the push–pull resonant inverter in phase with the linear amplifier. Moreover, a quasi-trapezoidal voltage output driving circuit is designed to decrease the drive losses, and a multiresonant network with a 180° phase shift is also presented in this article to produce a sinusoidal driving voltage to avoid the shoot-through problem. This structure serves the 100 MHz RF band, In future, this hybrid structure could be applied in the transmitter of microwave power transmission (MPT) system. Finally, a 100 MHz/20 W prototype was built to verify the theoretical analysis.

This article presents a novel architecture of power generator in microwave power transmission (MPT), which serves as the transmitter with directional radiation in the MPT system. A new structure based on quadrature modulation and demodulation technique is proposed, which features low cost, easy implementation, and high performance. Full amplitude and phase control of the radio frequency (RF) power is realized, providing the chance to achieve the direction functions of the MPT system. To radiate microwave power into free space, a $2\times 2$ phased array antenna is used in this article. Since the operation frequency is 915 MHz and energy focusing in the near field, the distance difference between each array elements with the target cannot be ignored. Therefore, based on the transmitter, a new strategy of directional radiation in the near field for power focusing is also presented in this article. The current phase difference between the array elements is calculated by using the proposed strategy. Finally, a prototype with 16-channel 100-W/915-MHz power transmitter, phased array antennas, and receiver are constructed in the laboratory to verify the theoretical analysis and test overall efficiency. The simulation and experimental results are shown to verify the effectiveness of presented power generator and its directional radiation strategy.

This article presents a low-cost circuit that generates narrow pulses with programmable waveform, amplitude, and position based on the spectrum stitching method. Specifically in this article, narrow pulses are generated through stitching the spectra of five subsignals, and the subsignals are generated by three regular arbitrary waveform generators with a bandwidth of 200 MHz. The experimental results of pulse generation with various waveforms, amplitude profiles, and position profiles are demonstrated. The pulses demonstrated in this article have a pulse width between 2 and 4 ns, with spectral coverage of about 500 MHz, which is well beyond the capacity of each of the three arbitrary waveform generators used in this work. The experimental results of this article indicate that the spectrum stitching technique has excellent potential to increase the effective bandwidth of arbitrary waveform generators using low-cost circuits.

Directional radiation (DR), a distinguishing feature of a microwave power transmission (MPT) system, suitably shapes and properly steers an intensified beam toward a specific target area. Coupling more radiated energy to the receiving aperture, DR technique benefits system efficiency and brings great flexibility, which entails further investigation. This article addresses DR realization from a system perspective. A novel architecture of MPT transmitter is proposed, which equips the system with multiple independently controlled RF power outputs and serves as a solid hardware basis for DR realization. Three DR algorithms are also introduced, providing convenient methods to obtain maximum receiving power for the receiver via software control. A 915 MHz/100 W MPT transmitter is fabricated in the lab, and an MPT verification platform is also constructed. Proposed architecture and algorithms are fully verified with experiments, which show a good performance in DR realization.

Background Enhanced recovery after surgery (ERAS) is a perioperative management protocol to accelerate patient recovery. This study aimed to evaluate the feasibility of ERAS protocols implemented in patients who underwent neoadjuvant chemotherapy (NACT) before minimally invasive McKeown esophagectomy. Methods This retrospective study compared the short-term clinical outcomes in esophagectomy patients from June 2018 to June 2021. Subjects were divided into two categories: those who underwent NACT (NACT group) and the non-NACT group. Results There was no significant difference in total postoperative complication morbidity between the NACT and non-NACT groups (21.2% vs. 20.7%, P=0.936). In addition, the hospital length of stay post-surgery (7.90 vs. 7.71 days, P=0.424) was not significantly longer when compared to the non-NACT group. The time to chest tube removal (5.37 vs. 5.13 days, P=0.238) and first bowel movement (2.92 vs. 3.01 days, P=0.560) was also similar between the two groups. Conclusions There was no significant difference in postoperative complications rate, postoperative hospital length of stay, and readmission rate between the two group. This study proved that ERAS protocols seemed to be safe and feasible for patients who received NACT before esophagectomy.

With the urgent demand for multitargets applications which used in long-range wireless power transmission (WPT) system, adaptive power transmission which used in microwave power transmission (MPT) system has caused widespread concern. This paper proposes a target-ware, power adaptive transmission method to fulfill this requirement. Based on the data returned by the targets, the microwave power beam is divided into multiple beams and transmitted to multitargets by the phased array antenna in the transmitter. According to the strategy, the power adaptive transmission method by adjusting the phase difference between distributed transmitter is implemented. Moreover, the closed-loop control schemes based on receiver and transmitter is also adopted. Finally, a 5. 8GHz/100W MPT system with two-targets is built and the theoretical analysis is proved by the experimental results.

Microwave power transmission (MPT) has been one of the most promising systems in the far-field wireless power transmission system. In MPT system, the harmonic energy generated by conventional diode rectifying circuit has great impact on the overall efficiency. Moreover, the passive impedance network leads to power reflection, which is the other factor leading to the overall efficiency decline. In this study, a 10 W output 100 MHz two-stage adaptive impedance-matching rectifying circuit is proposed which can make input impedance constant. About 100 MHz belongs to the band of radio frequency (RF) and the conception of microwave. The first-stage rectifier is modelled mathematically, which plays an essential role in constructing the initial input impedance and designing the control method of second-stage converter. By adjusting the duty cycle of the second-stage converter, the impedance of the whole rectifier realises 50 Ω under various input and the output conditions by means of simulations and experiments. The simulation and experimental results are shown to verify the effectiveness of the proposed RF to direct current converter and its control method. The overall efficiency with full load is up to nearly 65%.

The paper presents a self-switching rectifier circuit, which serves the receiver of Microwave Power Transmission (MPT). After taking a brief review of the current research on microwave rectifier circuits, a new rectifier circuit suitable for different input power is proposed, which has the advantages of simple structure and low cost, and it can realize adaptive control of a wide-range of input power. System structure and operation principle are elaborated in detail. Finally, a microwave rectifier circuit model of 5.8GHz was built, where the experiment-measured efficiency is all more than 50% in the range of 22~33dBm and the maximum is 68.2% at 28dBm. The proposed design is fully verified.

Microwave power transmission (MPT) is one of the most promising techniques to achieve long-distance wireless power transmission. Working in radio frequency (RF), the transmission line (TL) topology of class E power amplifier (PA) is an essential candidate for the MPT system, acting as the role of DC-RF conversion. PA’s performance significantly affects the efficiency of the whole system. However, there are few specific accurate design methods of TL class E PA. This paper presents a novel method to design TL class E PA in a mathematical way. The proposed method can strictly convert lumped element topology of class E PA to TL topology, regardless of different types of matching network. To minimize impedance discontinuities in the TL topology, an optimal strategy is also presented. The proposed strategy can help reduce return loss and increase power added efficiency (PAE). A 2.5GHz/10W high efficiency TL class E PA is constructed to verify the proposed method and the optimal strategy. As all simulation and experimental results indicate, the proposed method can accomplish a precise design of high efficiency TL class E PA.

This paper presents a kind of radio frequency (RF) power generator with ability of directional radiation in microwave power transfer (MPT) system. This power generator uses quadrature modulation which can regulate amplitude and phase as a close loop. In this paper a novel strategy for directional radiation in the near-field of MPT system is also presented. Operation frequency is 915MHz, output power is 15W and transmission distance is 1m. Directional radiation in MPT system requires phase shifters in order to change the current phases about the elements in antenna array. To compensate the insertion loss of phase shifters, the technique of quadrature modulation is used in this power generator, which maintains the amplitude even though the phase changes. Finally, a prototype is built to verify the theoretical analysis.

Microwave power transfer (MPT) is one of the most promising systems in the long distance wireless power transfer system. In MPT system, conventional diode rectifying circuit produces harmonic energy which has great impact on the overall efficiency as well as the power reflection. In order to gain adaptive impedance matching and high efficiency, this paper applies power electronic devices and topology to construct a two-stage 100MHz converter. 100MHz belongs to the radio frequency (RF) and belongs to the conception of microwave frequency. The two-stage adaptive impedance matching circuit and its control method are evaluated by simulations. The design of microstrip antenna is also presented in this paper, experimental results are shown to verify the effectiveness of the proposed RF-DC converter and the efficiency is up to nearly 65% as well.

The paper presents a novel architecture of RF power generator, which serves as the transmitter in microwave power transmission (MPT) system. Existing architectures for MPT transmitter are briefly reviewed, problems of which are analyzed. A novel structure based on quadrature modulation and demodulation techniques is proposed, which features low cost, easy implementation and comparable high performance. Full amplitude and phase control of the RF power is realized, providing the chance to achieve versatile functions in MPT system. Operation principles and design considerations are elaborated in detail. Finally, a 16-channel 90W/915MHz prototype is constructed in the laboratory. The proposed architecture and related control strategy are fully verified on the prototype.