微波化学反应器介质耦合窗应力计算分析与设计

微波能量耦合窗口是微波化学反应器的关键部件,它应该尽可能小地反射微波能量以避免烧毁功率源,同时密闭反应腔体以分隔反应物与微波装置。根据多物理场耦合模型,利用有限元方法对耦合窗进行了结构应力计算和设计,分析了微波加热过程中介质耦合窗的受热和热应力特点,得到了对工业应用具有参考价值的结果。提出可以通过设计适宜的介质垫片来降低窗体应力,提高可靠性。     

High temperature dielectric properties measurement system at 915 MHz based on deep learning

A ridged waveguide and heating system based on deep learning for dynamic measurement of dielectric properties at high temperatures has been developed. Firstly, specially designed ridged waveguide at the frequency of 915 MHz was utilized. The finite difference time domain simulation was then combined with the deep learning algorithm to construct the dielectric properties. In addition, the calibration method based on a two‐point algorithm was involved in the network. The precision of the measured dielectric constant and loss tangent was improved by 4.4% and 1.9%, respectively. Simulated results indicated that the deep learning algorithm had higher accuracy than back propagation neural networks and support vector machine algorithms. The reliability of the system was verified by Si₃N₄ and alcohols at room temperature. The dielectric properties of quartz particles were also tested over a temperature range up to 900°C. The experiment results agreed well with the reference values. This system can measure a wider range of dielectric properties and achieve higher accuracy using the advanced deep learning algorithm. It is more convenient to measure large size materials in industrial applications at high temperatures.     

A novel suspended stripline‐fed printed square slot array antenna with high‐gain

A novel suspended stripline‐fed square slot array antenna with high gain is presented. Its basic structure is a suspended stripline comprising of three layers. On the top layer, 4 × 4 square slots are etched and act as radiation elements. The middle layer consists of a suspended stripline power divider, and the bottom layer is a metal ground. After optimization by a parallel Genetic Algorithm (GA) on a cluster system, a prototype antenna is fabricated and tested. The measured results agree well with the simulated data, and show a high gain of 18.7 dBi and an impedance bandwidth of 5.7% for S11<‐10 dB are obtained. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

A K/Ka‐band dielectric and metallic 3D printed aperture shared multibeam parabolic reflector antenna for satellite communication

A K/Ka‐band (22‐33 GHz) high‐gain aperture shared multibeam parabolic reflector antenna is proposed. It performs a two‐dimensional beam scanning from a shared single parabolic reflector by introducing off‐focal feeds. The feed array is placed on and off the focal of the parabolic reflector. Traditionally, the feed blockage has a great impact on the performance of the antenna, which reduces the gain and increases the sidelobe level. The purpose of this paper is to suppress the negative effects of feed blockage by using hybrid material processing method. Both dielectric and metallic 3D printing technologies are used for antenna fabrication. The parabolic reflector antenna is printed by selective laser melting using aluminum alloy. The feed array and the supporting structures are printed by stereolithography apparatus in resin to control the blockage. The method helps to suppress the sidelobe level from ?10 to ?15 dB and to enhance gain by up to 2.3 dBi. The reflection coefficient is less than ?10 dB, while the coupling coefficient between the ports is less than ?20 dB over the entire designed band. At 31.5 GHz, the simulated maximum gain of the antenna are 30.7, 29.1, and 29.7 dBi, when different port separately excites. Multiple beams at ±15° and 0° are observed on both E‐ and H‐planes. Besides, it also verifies the possibility to use dielectric and metallic 3D printing technologies in hybrid for microwave device fabrication.     

Accordion microwave oven for uniformity and efficiency heating

Conventional microwave oven heating has the problem of poor heating uniformity and low heating efficiency. A novel microwave oven heating model has been proposed for improving heating uniformity by making the electric field in the microwave oven drastically change by changing the geometry of the microwave oven during the heating process. The transformation optics method is used to solve the computational difficulties caused by the continuous change of the mesh during the motion. Finally, the experiment verified the correctness of the simulation. In addition, important factors affecting heating efficiency were discussed.     

基于SIW的介电系数宽带测量装置

自20世纪80年代以来, 微波能的应用几乎扩展到了化学、材料、医学等各个领域。而微波能的应用实际上都直接或间接地与物质的介电特性相关。通过了解物质介电特性，就能研究它们对于微波的吸收和反射情况。因此，微波能应用中的介电系数测量显得尤为重要。而传统的测量方法实现在线测量时有一定的局限性，针对上述问题设计了新型的测量装置，结合神经网络算法对物质的介电系数进行了仿真计算，得到了一些有参考价值的数据，这些工作将对微波能的应用提供帮助。