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针对高超声速飞行器毫米波天线罩的工作环境和要求,分析毫米波天线罩电性能设计的难点。通过与低频段低速天线罩在设计上的比对,分别从天线罩厚度、入射角、材料介电性能3个关键的物理量入手,梳理影响毫米波天线罩电气性能的主要因素。根据已有防热透波材料体系,在继承低频低速天线罩二维射线追踪理论设计方法,并且充分考虑毫米波天线罩电气性能新特性的基础上,综合提出高超声速飞行器毫米波天线罩材料选择及壁厚精确设计方法。通过电磁仿真和实测数据的对比评估毫米波天线罩的电性能,验证了天线罩设计方法的正确性。 相似文献
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根据液晶材料在毫米波段良好的介电特性和调谐能力,设计了一款基于液晶材料的毫米波带宽可重构宽带带通滤波器。滤波器使用一个高通滤波器和一个低通滤波器级联实现带通效果;在低通部分加载液晶材料,通过调谐液晶材料的等效介电常数改变低通滤波器的响应频率,实现带宽的可重构。仿真结果表明,当调谐液晶介电常数从2.4变化到3.8时,滤波器的高频截止频率从52 GHz下降至48 GHz,相对带宽从84.9%变为78.3%。 相似文献
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介电弹性体是一种新型功能材料,其能量收集作用主要应用在低频、大变形的能量源场合,与海洋能发电十分契合。该文描述了介电弹性体发电的基本原理及其材料特性和发电装置电极材料的研究进展。针对目前介电弹性体海洋能发电装置成本高,种类少,能量转换效率低等问题,该文总结了国内外不同类型的基于介电弹性体的海洋能发电装置及研究方案,对不同类型的发电机特点及适用场合进行了分析。结果表明,浮标式和管状水动力式发电机应用前景广。最后阐述了当前介电弹性体在海洋能应用上亟待解决的问题,并对进一步解决上述问题提出了建议。 相似文献
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热释电探测器过去多用于10μm甚至更短的波长,因为大多数热释电材料在这一波长范围具有最佳吸收特性。但研究表明,诸多材料在毫米波段仍然能保持较强的吸收,这就为热释电效应应用于毫米波激光探测提供了理论依 相似文献
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在毫米波段,梳形线慢波系统与其它慢波系统相比,尺寸较大,易于加工,散热性好,很适宜用作毫米波返波管的慢波结构。本文通过对用场匹配法分析了梳形线色散特性的耦合阻抗,讨论了梳形线的尺寸对其色散和耦合阻抗的影响,为设计梳形线毫米波返波管提供了理论依据。 相似文献
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不同类型降水对毫米波传播特性的影响研究 总被引:2,自引:1,他引:1
为了提高复杂降水条件下毫米波传播衰减的评估精度,通过分析多个地区的降水谱特征,得出具有代表性的层状云降雨、积层混合云降雨、积雨云降雨以及干雪、湿雪的谱分布参数,然后结合降水粒子的形状、相态、介电模型,计算降水体目标在毫米波波段的散射特性.结果表明,降水强度不是唯一影响毫米波传播衰减的因素; 降水粒子相态、谱分布、入射波频率和温度等对毫米波传播特性均有不同程度的影响,其中谱分布和数密度是影响降雨对毫米波衰减的主要因素; 冰水构成比例是影响降雪对毫米波衰减的主要因素; 不同相态的降水,尤其是干雪、湿雪和雨对毫米波传播影响的差异较大; 而温度的影响较小.并建立了考虑谱分布和温度的降水衰减模型. 相似文献
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《光纤与电缆及其应用技术》1987,(5)
近年来毫米波频段的研究工作在国内方兴未艾。在毫米波技术中,介质材料的应用比之于微波波段更为广泛,所占的位置也更为重要,对介电参数的精度要求也更高一些。我所为配合毫米波技术研究工作的需要,开展了8毫米频段的低损耗介质材料测试方法的研究,业已能对介电常数ε=1~10范围的材料进行测试,精度优于1%,样 相似文献
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This article calculates the effect of changing building materials' permittivity and conductivity on electromagnetic wave transmission property analyses the power control strategy in mobile communication system, then sums up the relationship between the change of building materials' permittivity and conductivity and energy consumption in mobile communication system, and then points out the necessity of developing functional materials which can easily transmit electromagnetic wave to reduce energy consumption and electromagnetic pollution, so a new energy saving method by improving wave transmission property to reduce energy consumption of mobile communication is advanced. 相似文献
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Suga R. Hashimoto O. Pokharel R.K. Wada K. Watanabe S. 《Electromagnetic Compatibility, IEEE Transactions on》2005,47(4):866-871
Radiowave absorbers are frequently used in high power applications, such as radar sites, and the rise of temperature of the absorber has often become a matter of concern. In this paper, the finite-difference time-domain (FDTD) method combined with the heat transport equation (HTE), also known as the FDTD-HTE method, which has been widely used in the analysis of microwave heating or temperature increase in the human head due to portable phones, is used in the analysis of the wave absorption characteristics of a single-layer wave absorber. The complex permittivity of a sample made of epoxy resin, measured by a cavity-resonator method when the sample is irradiated by a high power field for different irradiation times, is used in the analysis, and the wave absorption characteristics of the absorber under investigation highly depend on the input power and irradiation time of the high power field. 相似文献
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It Is well known that the temperature rise in a material modifies its physical properties and, particularly, its dielectric permittivity. The dissipated electromagnetic power involved in microwave heating processes depending on ε(ω), the electrical characteristics of the heated media must vary with the temperature to achieve realistic simulations. In this paper, we present a fast and accurate algorithm allowing, through a combined electromagnetic and thermal procedure, to take into account the influence of the temperature on the electrical properties of materials. First, the temperature dependence of the complex permittivity ruled by a Debye relaxation equation is investigated, and a realistic model is proposed and validated. Then, a frequency-dependent finite-differences time-domain ((FD)2TD) method is used to assess the instantaneous electromagnetic power lost by dielectric hysteresis. Within the same iteration, a time-scaled form of the heat transfer equation allows one to calculate the temperature distribution in the heated medium and then to correct the dielectric properties of the material using the proposed model. These new characteristics will be taken into account by the EM solver at the next iteration. This combined algorithm allows a significant reduction of computation time. An application to a microwave oven is proposed 相似文献
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针对带孔缝矩形金属腔体在电磁辐射下的屏蔽效能问题,利用基于时域有限积分法的电磁仿真软件CST,建立了平面波辐照条件下含孔缝金属腔体的耦合模型,重点研究了电场极化方向,腔体材料,矩形孔缝的长度、宽度和深度,孔缝填充介质介电常数及其厚度等参数对屏蔽效能的影响规律.研究结果表明:典型金属材料对屏蔽效能的影响差别不大,垂直于电场极化方向的孔缝边长更能影响腔体的屏蔽效能,孔缝尺寸会影响矩形金属腔体的谐振点,孔缝深度能够通过衰减入射波在一定程度上影响屏蔽效能,孔缝填充介质会降低屏蔽效能,介质厚度及其介电常数会影响屏蔽效能峰值点.研究结果对金属腔体的电磁兼容设计有一定的指导意义. 相似文献
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Henderson G.N. Gaylord T.K. Glytsis E.N. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(11):1643-1659
A comprehensive set of analogies between ballistic electron wave propagation in semiconductors (arbitrary kinetic energy and effective mass) and electromagnetic propagation in general dielectrics (arbitrary permittivity and permeability) is established. The expressions for electron wave propagation, reflection, and refraction are developed and shown to have the same functional form as in electromagnetics, if analogous definitions of electron wave phase and amplitude refractive indexes are used. The reflectivity characteristics such as total internal reflection (critical angle) and zero reflectivity (Brewster angle) are analyzed as a function of material parameters for both general dielectrics and semiconductor materials. The critical angle and Brewster angle results are then applied to electron wave propagation in Ga1-xAlxAs, where it is shown that all interfaces in this material will have both a critical angle and a Brewster angle due to differing effective masses across the interface 相似文献
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精确测量低损耗微波材料的复介电常数十分重要。利用带状线法测量微波介质基板常温和变温的复介电常数,得到了高精度的测试结果。结果表明了用带状线法测量低损耗微波介质基板复介电常数的有效性和准确性。还分析了带状线测试方法中产生的误差和应该注意的事项。 相似文献
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小体积生物组织进行微波热疗过程中,热疗天线辐射的微波能量聚焦体积过大、治疗范围超出热疗目标区域烧伤其余健康组织,针对这一问题,文中提出了一种小型化体外挽袖式微带热疗天线。它由SMA连接器法兰盘两侧焊接的挽袖圆铜壳及两个圆形微带贴片组成。微带贴片的介质基底是相对介电常数为4.4的FR-4材料,基底厚1.6 mm。实测天线在915 MHz的反射系数为-18.5 dB,试验中由该天线加热40 mm×40 mm×40 mm的小体积猪肉组织,并采取红外热成像仪和热电偶两种测温方式测试天线加热情况,研究结果表明该天线有效治疗区域为20 mm×20 mm×10 mm的半椭球型,温度分布较为均匀,适用于小体积体外微波热疗系统。 相似文献
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激光打孔过程是激光与物质相互作用的复杂物理过程,涉及物质在激光作用下的多种物态变化。为模拟激光打孔过程,将物质状态随加热时间的变化等效于无限大介质内部热源功率密度分布随时间的变化,采用热物性参量为恒量的无限大均匀介质中热扩散方程的解为理论工具,给出了该过程的近似数学表达式,并编制软件模拟了激光打孔的孔洞形成过程。模拟计算表明,所设计的软件能够模拟一个合乎逻辑的材料孔洞形成的过程,如果改变计算参量,则可以实现不同形状的孔洞。该研究将为工业生产中激光加工工艺的制定或激光辐照下材料的热损伤快速估计提供一种快捷的工具。 相似文献