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16. Introduction

Author

Huang, Kama, Yang, Xiaoqing, Zhu, Huacheng, Huang, Kama, Yang, Xiaoqing, and Zhu, Huacheng

Published
2021
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23. A high-performance microwave plasma source employing dielectric wedges.

Author

Yang, Fengming, Zhang, Wencong, Huang, Kama, Yang, Yang, and Zhu, Huacheng

Subjects
PLASMA sources, DIELECTRIC materials, DIELECTRICS, DRUDE theory, ENERGY conversion, MICROWAVE plasmas, MICROWAVES, COLLISIONAL plasma
Abstract

The microwave-to-plasma energy conversion efficiency and the ease of plasma self-ignition are critical factors affecting the applications for microwave plasma sources (MPSs). This study presents a novel MPS utilizing dielectric wedges for self-ignition and improved energy conversion. Firstly, we crafted a dielectric wedge with a gradient refractive index, guiding the electric field from air to dielectric materials and facilitating microwave propagation along the dielectric in a waveguide. Through electromagnetic simulation, we explored how the size and permittivity of the dielectric wedge affect the electric field distribution. Then, the MPS based on the dielectric wedge was designed. In this configuration, a dielectric tube encloses the discharge tube, connecting to dielectric wedges to guide electromagnetic waves to the plasma. We analyzed the MPS performance using the Drude model, evaluating microwave energy conversion efficiency across various electron densities and collision frequencies. The results were compared with a commonly used MPS based on a tapered waveguide, demonstrating the proposed MPS has wider applicability across different operation conditions. Finally, experiments under low pressures were conducted using various gases, showing an average energy conversion efficiency of approximately 40% higher than the tapered waveguide MPS. The experiments also indicate the proposed MPS has a greater capability of self-ignition at lower power levels. These findings highlight the efficacy of incorporating dielectric wedges to enhance MPS performance, making it conducive for broader industrial applications. [ABSTRACT FROM AUTHOR]

Published
2024
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33. Experimental Investigation on Electrical Conductivity Variation of Carnosine and Zinc Chloride Aqueous Solutions under Microwave Irradiation

Author

Zhao, Chenxi, Ma, Yun, Hou, Desheng, Wang, Lin, Hong, Tao, Tang, Zhengming, Huang, Kama, and Gou, Dezhi

Abstract

The mechanism of biological effects of environmental electromagnetic radiation is still not completely clear. The chelation of biological small molecule peptides with metal ions plays a very important role in human metabolism. In this paper, a special experimental system was designed to measure the conductivity of carnosine and zinc chloride mixed aqueous solutions under different concentration ratios, microwave powers, and temperatures. The experimental results show that, first, different concentration ratios can alter the conductivity change rate of the mixed aqueous solution. The conductivity of the solution always increases under microwave irradiation at a concentration ratio of 1:1. However, the conductivity is reduced by −0.04% with a 1:5 concentration ratio and 6 W microwave power at 10 °C. Second, temperature can alter the conductivity change rate of the aqueous mixture. The higher the temperature, the smaller the conductivity change rate. Third, different microwave powers can alter the conductivity change rate of the mixed aqueous solution. In general, the conductivity change rate increases with an increase in microwave power. Experimentally observed reduction of the conductivity change rate in carnosine and zinc chloride aqueous solution under low microwave power and low temperature indicates that microwaves do affect the chelation of carnosine with zinc chloride. This work provides a new perspective for the mechanism of explanation of microwave biological effects.

Published
2024
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34. A Polarization-Insensitive Rectifying Surface for 2.4 GHz WLAN Band RF Energy Harvesting

Author

Wang, Huai-Yu, Cheng, Fei, Yang, Yang, Chen, Xing, Wu, Li, Gu, Chao, and Huang, Kama

Abstract

This article introduces a polarization-insensitive rectifying surface for 2.4 GHz WLAN band RF energy harvesting. The unit cell of the rectifying surface is formed by combining an interdigital structure with a square ring structure, optimized for high RF harvest efficiency over a wide band. For optimal performance, our design employs a direct matching of the Schottky diodes to the rectifying surface, minimizing signal loss and enhancing rectification effectiveness. To demonstrate the concept, a $4\times 4$ element rectifying surface array was fabricated and measured, yielding a total efficiency of 21% at an incident power density of $2.62~\mu $ W/cm2. The measured total efficiency remains higher than 18.9% over the 2.4–2.57 GHz range, covering the 2.4 GHz WLAN band. Furthermore, the total efficiency remains constant despite variations in the polarization angle of the incident wave. Our design demonstrates a highly efficient rectifying surface for harvesting low-power energy within the 2.4 GHz WLAN band, offering a promising solution for powering wireless devices.

Published
2024
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39. Compact Slot Microstrip Patch Antenna Loaded with Open Metal Cavity for Microwave Hyperthermia.

Author

Hu, Kun, Xiao, Qi, Huang, Kama, and Gas, Piotr

Subjects
ANTENNA design, ANTENNAS (Electronics), IMPEDANCE matching, THERMOTHERAPY, MICROSTRIP antennas
Abstract

Cancer is a significant disease that often results in severe side effects from traditional treatments. Microwave hyperthermia has emerged as a minimally invasive, highly effective, and low‐toxicity treatment option that has gained widespread use in recent years. The primary objective of this study is to develop and assess a miniaturized slit patch antenna designed to operate at 2450 MHz for hyperthermia therapy. The octagonal antenna patch features four symmetrical slots to reduce its size, enhance directional radiation, and improve focusing and penetration depth. Additionally, a metal cavity is incorporated at the top of the antenna to create a gap between the antenna and the skin, allowing for skin heat dissipation, improved impedance matching, reduced outgoing radiation, and enhanced directional radiation. The performance of the antenna is assessed based on specific absorption rate (SAR), penetration depth (PD), and effective field size (EFS). Subsequently, the antenna is fabricated and tested in pork tissue, with the measured results demonstrating good agreement with the simulated outcomes. [ABSTRACT FROM AUTHOR]

Published
2024
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