K頻段高均勻度微波材料處理系統之模擬研究與實用驗證;Simulation study and practical verification of K-band high-uniformity microwave processing system

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题名:	K頻段高均勻度微波材料處理系統之模擬研究與實用驗證;Simulation study and practical verification of K-band high-uniformity microwave processing system
作者:	洪培修;Hung, Pei-Hsiu
贡献者:	物理學系
关键词:	微波材料處理系統;圓極化天線;分布作用振盪器;microwave processing system;circularly polarized horn antenna;extended interaction oscillator
日期:	2022-09-22
上传时间:	2022-10-04 11:17:40 (UTC+8)
出版者:	國立中央大學
摘要:	使用微波對介電材料進行熱處理已被廣泛應用於科學研究及材料製程上，而微波加熱速率正比於操作頻率及電磁場強度，此高頻、高功率的需求使得K-band EIO很適合作為微波材料處理系統的微波源。本文探討之EIO腔體採用具易加工及高功率乘載能力之雙重入式方形平台耦合腔作為慢波結構，由模擬及實測顯示，經調整適當的耦合孔位置及寬度可使此EIO於單模（0-mode）並穩定操作，經實測證實此EIO在電子束電壓17.4 kV、電子束發射電流550 mA的操作條件下，輸出功率可達1.776 kW，電子效率達18.56 %，共振頻為24.324 GHz。當以線性極化波對介電質進行加熱時，會因極化電荷屏蔽效應而導致加熱效果不均勻，尤其在處理高介電常數和非等軸比形狀的樣品時特別嚴重，此負面效應在可透過採用圓極化波來獲得改善。本文探討之單脊式K-band圓極化號角天線具有良好的極化轉換性能及易製性，模擬及實測證實此圓極化天線在23.5 GHz ~24.5 GHz之頻率範圍區間，反射損失低於-20 dB、指向軸長比低於0.7 dB且天線增益大於20 dB，此新設計之圓極化號角天線結構簡單並較其他形式極化器適用於高功率操作。經由模擬方式驗證，高頻及高功率之圓極化波可顯著提升加熱速率及均勻性，使K-band EIO及圓極化天線適合應用於微波材料處理系統，更可廣泛應用於通訊系統中。;Microwave heating for dielectric material processing havs been widely employed in scientific research and manufacturing. Microwave heating rate is proportional to the operating frequency and the intensity of the electromagnetic field. The high frequency and high-power requirements make K-band extended interaction oscillators (EIO) a suitable candidate for microwave processing systems. A square doubly reentrant coupled cavity is proposed as a slow-wave resonant structure in K-band EIO in this study due to its easy fabrication and high-power capability. The EIO is designed to be operated at single 0-mode, and the simulation results show that the competing π/5-mode can be effectively suppressed by properly choosing the width and location of the output coupler. A stable, single-mode and high-performance operation of EIO is thus successfully demonstrated by simulation and experiments in the paper. The experimental measurement gives maximum 1.776 kW output power (18.56 % electronic efficiency) and wave frequency 24.324 GHz at beam voltage 17.4 kV and beam current 550 mA. Polarization-charge shielding may result in uneven power deposition in the samples when a linearly polarized wave is used, especially for samples with a relatively high permittivity and particular shape of the aspect ratio. Uneven heating and excessive temperature spread during microwave processing can be remedied by using a circularly polarized wave. A single-ridged K-band circularly polarized horn antenna offering excellent performance has been developed by improving the polarization conversion and manufacturing complexity. The numerical and experimental results are consistent showing the performance of the circularly polarized horn antenna to be sufficient to meet the requirements of K-band microwave processing systems with <-20 dB return loss, <0.7 dB axial ratio at the boresight direction, and >20 dB power gain in the frequency range from 23.5 GHz to 24.5 GHz. The newly designed circularly polarized horn antenna has a simple structure and outperforms many existing circular polarization devices in high-power operations. It has been verified by simulation that a circularly polarized wave with high-frequency and high-power can significantly improve the heating rate and uniformity. These properties make microwave devices such as K-band EIOs and circularly polarized antennas suitable for use in microwave processing systems. These microwave devices can also be widely applied in communication systems.
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