加工工艺对微波窗材料介电性能的影响

聚四氟乙烯、聚乙烯、有机玻璃等介质材料因其良好的透波性能和优异的机械性能被广泛用作高功率微波的输出窗口，但关于窗口加工处理工艺对材料介电性能的影响却少有研究。利用高压电桥及高阻计对不同介质材料不同工艺下的基本介电参数进行了测量，利用静电感应法对不同介质材料表面0.8~0.9 eV浅能级的电子陷阱密度分布进行了测试，利用波导口开展了S波段800 MW、百ns微波脉冲作用下的介质击穿实验，考察了材料表面粗糙度、划痕对介质窗表面击穿的影响。结果表明:烘烤工艺在一定程度上降低了材料的耐击穿性能，增加了介质损耗；平行于电场方向的划痕形成了材料表面击穿的通道，而该通道的存在又进一步加剧了击穿的发生。

Influence of processing technology on dielectric porperties of microwave window materials

Polytetrafluoroethylene(PTFE), polyethylene(PE), polymethyl methacrylate(PMMA) and other similar medium materials are widely used for making of output window of high power microwave(HPM), due to their favorable wave-transparent and mechanical properties. But there are few studies conducted on the influence of different processing technologies on dielectric properties of these materials. In this article, the basic dielectric parameters of different medium materials processed with different technologies are measured with high-pressure bridges and high resistance meters, and the surface electrical trap densities of these materials at the low energy level of 0.8-0.9 eV are measured with the adoption of electrostatic induction method. Medium breakdown experiments with waveguides under S band, 800 MW and 100 ns microwave pulse are conducted, and the effects of different material surface finishes on window surface breakdown are studied. The results show that, the baking technology to some extent reduces materials resistance to breakdown, and causes more dielectric losses; the scratches parallel to the direction of electric field form the channel for material surface breakdown, leading to more serious breakdown.