基于超材料角反射面的高增益高效率双圆极化Fabry-Perot天线设计

基于射线跟踪模型,提出了一种超材料角反射面结构,实现了Fabry-Perot天线增益和口径效率的提升.首先对基于超材料角反射面的Fabry-Perot天线进行了理论推导和分析.然后,设计并分析了双圆极化馈源、基于超材料角反射面的Fabry-Perot天线及其性能.最后,对所提出的Fabry-Perot天线模型进行了制造和测试.结果表明,该天线的左圆极化增益和右圆极化增益分别为21.4 d Bi和21.3 d Bi.相比馈源天线,增益分别提高了16.4 d B和16.3 d B.与传统Fabry-Perot天线相比,所提出超材料角反射面同时充当了反射面和相位校正面,实现了对Fabry-Perot天线边缘电磁波的有效调控.所设计Fabry-Perot天线工作在2.8 GHz频段,具有高增益、高口径效率和低旁瓣的优点,满足了太阳射电望远镜F107指数观测的需求.     

立方角锥棱镜的有效反射区

定义了立方角锥棱镜的有效反射区 ,证明了立方角锥棱镜底面角部区域 (即非有效反射区 )入射光与出射光不平行 ,并且在入射光垂直棱镜底面入射情况下计算得有效反射区的面积为底面的三分之二。     

带直角反射器的太赫兹等离子体-金属混合天线

为了满足可工作于太赫兹频段以及较好的方向性和高增益的需求,在等离子体天线的基础上提出了新型等离子体-金属混合八木天线,在其中将反射振子替换为夹直角反射板。根据等离子体天线及八木天线设计理论,设计了该天线的结构并初步确定了其结构参数。通过电磁仿真研究了不同天线-顶点间距情况下天线的回波损耗、增益、电压驻波比和辐射方向图,最终实现了结构参数优化。与不带反射板的天线的对比结果表明,该结构具有更高的增益与更优的前后比。     

Antenna patterns of an open structure mixer at a submillimeter wavelength and of its scaled model

To verify the enhancement in sensitivity of a Schottky barrier diode using a 90° corner reflector at submillimeter wavelength a 651 scaled model of the open structure mixer was constructed and investigated at 2.8 cm wavelength.The results show clearly the advantage of a 90° corner reflector, the reality of the deviations for 45° and 60° corner reflectors found for submillimeter wavelengths, and the equality of the antenna patterns for a 90° corner reflector and a cat-eye (corner cube) reflector.     

化学氧碘激光器中的角立方反射器的研制

分别利用电子束蒸发和离子束溅射手段在单晶硅基底上制备了54.7°入射1315nm和632.8nm双波长高反射薄膜,并对两种手段所镀制薄膜地性能进行了比较;然后对离子束溅射所镀制的反射镜进行了胶合,得到了高精度的角立方反射器。最后,将所制备的角立方反射器实际用于化学氧碘激光谐振腔后,获得了近衍射极限的激光输出。     

Investigation of a heterodyne receiver with open structure mixer at 324 GHz and 693 GHz

The performance of a submillimeter heterodyne receiver using an HCOOH laser local oscillator and an open structure mixer with a Schottky barrier diode has been optimized for 693 GHz. Working at room temperature a single sideband (SSB) system noise temperature of 7,300 K, a mixer noise temperature of 6,100 K and a conversion loss of 12 dB has been achieved. The same receiver system has been investigated at 324 GHz using an HCOOD laser local oscillator yielding a noise temperature of 3,100 K (SSB), a mixer noise temperature of 2,400 K (SSB) and a conversion loss of 10 dB (SSB). An acousto-optical spectrometer has also been constructed, with 1024 channels and a channel-bandwidth of 250 kHz. The system NEP per channel was 2.5×10^–17 W/Hz^1/2 at 324 GHz and 5.0×10^–17 W/Hz^1/2 at 693 GHz.     

基于猫眼腔镜损耗调节的激光横模演示系统

提出一种基于猫眼腔镜损耗调节的新型激光横模演示系统。采用半外腔He-Ne激光器,利用由分立的可进行五维微调的凸透镜和凹面镜组成的猫眼逆向器构成损耗可调激光谐振腔,通过调节猫眼逆向器改变激光谐振腔的损耗比，实现改变激光横模状态的作用。利用CCD进行图像采集，计算机实现图像存储，从而得到20多种结构清晰的高阶横模花样图片。     

Design of a Quasi-Optical System to Convert TE0n Mode Outputs of a Gyrotron into Gaussian Beams

In this paper we present a novel design of a quasi-optical system for conversion of gyrotron outputs into gaussian beams. It consists of a quasi-optical antenna, four focusing mirrors (parabolic cylinders) and a filter which removes the side lobes of the beam. The system is capable to convert three TE_0n mode outputs into gaussian beams with waist size of 16.7 mm as well as four TE_1n mode outputs into bi-gaussian beams with waist size of 10.9 mm in width and 16.5 mm in length.     

角锥阵列改善固体热容激光器光束质量

 为改善光束远场质量,探索研究了角锥反射器的应用,利用角锥棱镜的准相位共轭特性,将角锥棱镜阵列作为热容激光器的后腔镜,抑制腔内波前畸变,并通过数值模拟计算对角锥阵列的单元边长进行优化设计。实验结果表明:角锥阵列对光束远场质量有明显的改善,当角锥阵列的单元边长为4 mm时,实现光束远场7倍衍射极限输出。     

物理光学法分析反射面天线辐射场

利用物理光学方法分析天线的远区辐射场具有计算速度快和内存需求少的特点,目前已被广泛应用于反射面天线的远区辐射场计算中。推导了利用斯特拉顿-朱兰成远场积分方程计算天线远区电场的表达式,计算了某一偏馈反射面天线的方向性,与文献中已有结果比较表明,方向图结果是正确的。馈源的方向图模型设置为余弦函数的q次方,利用增益公式近似推导了天线的增益,将这一计算方法应用于赋形反射面天线的远场分析中,通过对比反射面天线赋形前后波束扫描过程中不同扫描角度处的方向图,验证了赋形设计对于提高天线增益平坦度的有效性。     

带有反射腔的相对论返波管初步实验研究

阐述了带有反射腔的相对论返波管的初步实验研究进展。反射腔是一段不规则的圆波导,在相对论返波管中起到截止颈的作用。初步实验的结果为：外加磁场Bz =0.82T时,输出微波功率为170MW,微波频率8.874GHz,脉宽为10ns;外加磁场Bz =1.7T时,微波功率为370MW,频率与脉宽不变;根据辐射场功率密度分布判定传输模式为TM01模。结果表明：带有反射腔的返波管在较低外加磁场下也能够工作。     

24 GHz宽波束阵列天线的设计

利用Rogers 5880为介质材料设计了一款应用于车载防撞雷达前端的圆极化微带阵列天线,该阵列天线采用直线阵结构,运用了多个四分之一波长阻抗变换器实现了阻抗匹配。仿真和测试结果表明: 该阵列天线的阻抗带宽(S₁₁ < -10 dB)为23.45~25.65 GHz,最大增益为15.54 dB;轴比带宽24.56~25 GHz,轴比最小为1.25 dB;第一副瓣电平小于-20 dB,E面半功率波瓣宽度为10°,H面波瓣宽度为75°,其尺寸为70.94 mm×14.72 mm×0.508 mm。该天线具有高增益、低副瓣、体积小、性能稳定等优点,在汽车防撞雷达系统中有广阔的应用前景。     

带有反射腔的相对论返波管初步实验研究

 阐述了带有反射腔的相对论返波管的初步实验研究进展。反射腔是一段不规则的圆波导,在相对论返波管中起到截止颈的作用。初步实验的结果为：外加磁场B_z =0.82T时,输出微波功率为170MW,微波频率8.874GHz,脉宽为10ns;外加磁场B_z =1.7T时,微波功率为370MW,频率与脉宽不变;根据辐射场功率密度分布判定传输模式为TM₀₁模。结果表明：带有反射腔的返波管在较低外加磁场下也能够工作。     

Analysis and simulation of a 4H-SiC semi-superjunction Schottky barrier diode for softer reverse-recovery

In this paper, a 4H-SiC semi-superjunction (SJ) Schottky barrier diode is analysed and simulated. The semi-SJ structure has an optimized design and a specific on-resistance lower than that of conventional SJ structures, which can be achieved without increasing the process difficulty. The simulation results show that the specific on-resistance and the softness factor depend on the aspect and thickness ratios, and that by using the semi-SJ structure, specific on-resistance can be reduced without decreasing the softness factor. It is observed that a trade-off exists between the specific on-resistance and the softness of the diode.     

Analysis and simulation of a 4H-SiC semi-superjunction Schottky barrier diode for softer reverse-recovery

In this paper,a 4H-SiC semi-superjunction (SJ) Schottky barrier diode is analysed and simulated.The semi-SJ structure has an optimized design and a specific on-resistance lower than that of conventional SJ structures,which can be achieved without increasing the process difficulty.The simulation results show that the specific on-resistance and the softness factor depend on the aspect and thickness ratios,and that by using the semi-SJ structure,specific on-resistance can be reduced without decreasing the softness factor.It is observed that a trade-off exists between the specific on-resistance and the softness of the diode.     

一种匀光鳞甲反射罩设计

在灯具设计中,特别是开发投光灯、轨道灯等类型灯具时,经常会遇到系列化设计问题。在不修改基本外形结构的情况下,要想获得不同发光角度、照度均匀,提出了一种通过鳞甲片改变出光角度的反射罩设计方案,包括鳞片参数的计算、基面合理分隔方法、实际仿真模拟。最终给出同样基面,发散角(FWHM)为20°、40°、60°,光能利用率均达到75%,匀光效果85%左右的设计结果,证明该设计方法可行性。     

Induced focusing and conversion of a Gaussian beam into an elliptic Gaussian beam

We have presented an investigation of the induced focusing in Kerr media of two laser beams, the pump beam and the probe beam, which could be either Gaussian or elliptic Gaussian or a combination of the two. We have used variational formalism to derive relevant beam-width equations. Among several important findings, the finding that a very week probe beam can be guided and focused when power of both beams are well below their individual threshold for self-focusing, is a noteworthy one. It has been found that induced focusing is not possible for laser beams of any wavelength and beam radius. In case both beams are elliptic Gaussian, we have shown that when power of both beams is above a certain threshold value then the effective radius of both beams collapses and collapse distance depends on power. Moreover, it has been found that induced focusing can be employed to convert a circular Gaussian beam into an elliptic Gaussian beam.     

宽间隙反射器相对论返波管同频高阶模式抑制

实现输出模式控制和纯化是过模相对论返波管振荡器物理设计的关键。结合数值仿真和粒子模拟,对一种宽间隙反射器过模相对论返波管内的同频高阶模式激励及其抑制进行了研究,结果表明：模式转换和激励是同频高阶模式的直接来源,合理优化慢波结构、反射器和二极管参数,抑制由工作模式向高阶模式的转化效率,调整由二极管区反射回束波互作用区的模式相位,实现了过模相对论返波管的高效率工作和高模式纯度微波输出;所设计的宽间隙反射器过模相对论返波管输出微波功率中TM01模式的比例高于98%,功率转换效率约40%,工作频率为9.87 GHz。     

Enhanced thermal stability of Ag ohmic reflector for InGaN/GaN light-emitting diode using a Ru capping layer

A Ru capping layer is employed to improve the thermal stability of Ag ohmic reflectors for high-power GaN-based light-emitting diodes (LEDs). The 20-nm-thick Ru capping layer is shown to be fairly effective in suppressing agglomeration by forming RuO₂. The Ag/Ru contacts exhibit specific contact resistance of 8.1 × 10⁻⁵ Ω cm² and reflectance of ∼89% at a wavelength of 450 nm when annealed at 500 °C for 1 min, which are much better than that of Ag only contacts. Blue LEDs fabricated with the 500 °C-annealed Ag/Ru contacts give a forward voltage of 2.98 V at an injection current of 20 mA, which is lower than that (3.02 V) of LEDs with the 500 °C-annealed Ag only contacts. LEDs with the 500 °C-annealed Ag/Ru contacts show 25% higher output power (at 20 mA) than LEDs with the 500 °C-annealed Ag only contacts. X-ray photoemission spectroscopy examinations are performed to describe the improved electrical performance of the Ag/Ru contacts.     

三镜波束波导在高功率微波天线中的应用

通过对波束波导馈电卡塞格仑天线工作原理的分析,论述了波束波导在高功率微波辐射天线中的应用及设计方法,重点介绍了一套利用波束波导馈电高功率微波辐射天线。该天线利用由三面反射镜组成的波束波导对一个由两个抛物面镜组成的双反射面天线进行馈电,实现了波束的快速扫描。该天线工作在X波段时,功率容量大于1GW,天线增益大于50dB。