ESR spectrometer with a wide frequency range using a gyrotron as a radiation power source

The development of a high frequency electron spin resonance (ESR) spectrometer with a wide frequency range using a gyrotron as the radiation power source is described.GYROTRON FU-E, optimized for use in an ESR spectrometer in the millimeter wave range, was developed in Fukui University. In order to test the normal operation of the spectrometer, the ESR of two standard samples, single crystal and polycrystalline DPPH, has been measured, in the pulsed mode over the frequency range from 65 GHz to 135 GHz.     

Synchrotron radiation of electrons trapped in earth's magnetosphere

Relatively large fluxes of trapped electrons with energy above several tens of MeV in the inner radiation belt, established according to low altitude satellite measurements, invoked the question of their production of synchrotron radiation in geomagnetic field. Based on experimental data on electrons, rough estimate of the spectral density of synchrotron radiation at the Equator is obtained in the region of maximum emissivity. Relatively low value of the radiation flux implies that only precise measurements at 1 GHz allowing to measure the directivity of emissions may be relevant.     

Analysis on effect of low dielectric permittivity on indium-doped tin oxide based optically transparent terahertz patch antenna

Indium-doped tin oxide based optically transparent rectangular patch antennas are designed to resonate at 750 GHz; one on the glass substrate and the other on the polyimide substrate. Characteristics of both the transparent antennas such as impedance bandwidth, radiation efficiency, directivity and gain are analyzed and compared. Polyimide substrate has a lower dielectric permittivity than the glass substrate. The effect of low dielectric permittivity substrate on the radiation characteristics of the terahertz transparent patch antenna is analyzed. The transparent antenna on polyimide substrate is shown to have gain greater than 3.97dB in 714–795 GHz. The proposed transparent antennas are designed and simulated by using finite element method based electromagnetic solver, Ansys–HFSS.     

The research of high-directive anisotropic magnetic metamaterial antenna loaded with frequency-selective surface

This paper uses a Computer Simulation Technology microwave studio to simulate the performance of a new high-directivity anisotropic magnetic metamaterial antenna loaded with a frequency-selective surface. Frequency-selective surface with cross-dipole element has a great effect on the directivity, radiation pattern, and gain of such an antenna. The experimental results show that frequency-selective surface (FSS) significantly improve the radiation performance of anisotropic magnetic metamaterial antenna. For example, as a single anisotropic magnetic metamaterial antenna, half power beam width is 4 degrees in the H planes, and the gain of this antenna is 19.5 dBi at 10 GHz, achieving a 2.1 degree increment in half power beam width, and a 7.3 dB gain increment by loading with the FSS reflector. The simulating results are consistent with our experimental results.     

Spectrum Determination of Terahertz Sources Using Fabry-Perot Interferometer and Bolometer Detector

We describe a method to determine the radiation spectrum of terahertz sources using a transmitted Fabry-Perot interferometer and a bolometer detector. Our novel Fabry-Perot spectrometer can measure the spectrum of an unknown broadband sub-terahertz and terahertz source. The spectrometer does not need to be pre-tuned. We develop a new algorithm to support the measurements using this spectrometer. Our technique allows us to measure the spectrum over more than an octave, and our numerical algorithm is very stable and robust, providing for an accurate spectrum determination. Two Gunn oscillation sources with the main frequencies at 200 GHz and 600 GHz are used to test the proposed method. The spectrum extracted from the measured data shows that this method is accurate and reliable.     

Microwave frequency modulation in continuous-wave far-infrared ESR utilizing a quasi-optical reflection bridge

We report the development of the frequency-modulation (FM) method for measuring electron spin resonance (ESR) absorption in the 210- to 420GHz frequency range. We demonstrate that using a high-frequency ESR spectrometer without resonating microwave components enables us to overcome technical difficulties associated with the FM method due to nonlinear microwave-elements, without sacrificing spectrometer performance. FM was achieved by modulating the reference oscillator of a 13GHz Phase-Locked Dielectric Resonator Oscillator, and amplifying and frequency-multiplying the resulting millimeter-wave radiation up to 210, 315 and 420GHz. ESR spectra were obtained in reflection mode by a lock-in detection at the fundamental modulation frequency, and also at the second and third harmonic. Sensitivity of the setup was verified by conduction electron spin resonance measurement in KC60.     

一种新型宽带定向性贴片天线设计

利用超材料概念,通过在接地面上蚀刻条形缝隙图案,并引入"八木"天线中的反射器和引向器的设计思想,设计并且制作了一种超宽带强定向型贴片天线.仿真结果表明,天线相对带宽为65.3%(6.9—13.6 GHz),带内回波损耗均在-10 d B以下,整个频段内天线的增益均在4.4 d Bi以上.由于接地板上蚀刻的超材料结构的左手特性影响了天线介质基底的等效媒质参数,天线电磁场的传播方向被改变,天线辐射场主要集中在水平方向而不是传统贴片天线的垂直方向.在传统的贴片天线上引入反射器和引向器增强了天线的方向性.实验结果与仿真结果有较好的一致性.     

阵元间互辐射对基阵指向性的影响研究及试验

针对常规基阵指向性图计算并未考虑阵元间互辐射阻抗影响这一不足,修正了常规基阵指向性图计算公式。将阵元间的互辐射阻抗引入到水声基阵的辐射声场计算中,并依据叠加原理得到包含阵元间互辐射阻抗的基阵指向性图计算修正公式。15元均匀线列阵和5×5均匀平面阵的计算机仿真和消声水池试验结果表明,该修正公式相比于常规公式更能反映基阵指向性图的真实情况。      

Wide band (2.5 GHz) infrared heterodyne spectrometer

Conclusion A double beam heterodyne spectrometer with 2.5 GHz bandwidth was built in Reims. The receiver's bandwidth was measured by heterodyning radiation from a CO₂ laser with the radiation from a tunable diode laser. The spectrometer was used for laboratory studies. Ammonia absorption spectra were recorded. Line positions in agreement with other works were measured.This apparatus will soon be used for atmospheric ozone studies in association with an isotopic¹²C¹⁸O₂ laser to avoid atmospheric CO₂ absorption.     

含损伤黏弹性阻尼加筋层合板声功率和指向性变异*

该文旨在研究损伤位置和程度对自由阻尼加筋层合板声辐射功率和指向性的影响。基于Mindlin和Timoshenko梁理论,建立了自由阻尼层合板-梁组合结构有限元模型。数值求解四边简支边界条件自由阻尼加筋层合板振动响应,继而通过Rayleigh积分计算加筋层合板辐射声功率和指向性。将计算得到的前4阶模态固有频率、声辐射功率与指向性与已有文献进行了对比基本一致,验证了数值模型的正确性。最后,详细讨论了损伤位置和程度对自由阻尼加筋层合板固有频率、振型、声辐射功率和指向性的影响,结果表明：随着结构损伤程度的增大,声辐射功率峰值向低频移动,在更多角度上出现明显的指向性;声辐射功率和指向性对损伤位置比损伤程度更加敏感。     

4单元矩形径向线螺旋阵列天线的理论分析和数值模拟

 提出了一种便于组合的矩形径向线螺旋阵列天线。介绍了该矩形阵列天线的提出背景以及工作原理，分析了L型电磁组合探针的耦合特性，设计并数值模拟了中心频率为4.0 GHz的4单元矩形径向线螺旋阵列天线。模拟结果表明：该天线易于实现单元天线激励幅度和相位的均匀性及其随频率变化的平坦性。该口径为90 mm×90 mm 的天线在中心频率4.0 GHz 下，方向性系数为12.57 dB，轴向轴比值1.55；在3.60～4.05 GHz的频率范围内方向性系数大于11.6 dB，轴比小于1.55，反射系数小于0.2。     

加绕变升角宽频带椭圆螺旋天线

 椭圆螺旋天线的结构比传统的圆柱螺旋天线更加适合于卫星通信的终端,然而由于其圆极化特性变差而限制了其广泛应用。把改善轴向模螺旋天线辐射特性的两种方法结合起来应用于椭圆螺旋天线,提出了带有附加螺旋线的变升角轴向模椭圆螺旋天线。以一个5圈、短轴长轴之比为0.65的椭圆螺旋天线为例,用FEKO软件对其辐射特性进行了仿真。结果表明,这种方法提高了椭圆螺旋天线的方向性系数,同时具有较好的圆极化特性。在2.2~4.2 GHz频率范围内,最高增益为12.86 dB,比单绕均匀升角的椭圆螺旋天线提高了1.2 dB。     

L波段小型化同轴-共面波导定向耦合器

设计了一种适用于L波段高功率微波辐射场测量的同轴型定向耦合器。分别选择同轴线和金属底板共面波导（CBCPW）作为主副传输线,减小定向耦合器横截面积;利用小孔耦合理论和微元法对耦合结构进行理论分析,选择连续渐变的菱形耦合缝隙,缩短定向耦合器长度;采用数值模拟的方法对耦合器结构进行优化,并对其性能参数进行实验测试,结果表明, 在1~2 GHz频带范围内耦合度约为47 dB,方向性大于17 dB。     

液体中光击穿所激发声场的方向性研究

从液体中光击穿所激发声场的柱体模型和靶盘模型出发,运用声学基础的理论原理,提出了等离子体椭球模型,对光击穿所激发声场的方向性进行了理论研究.通过MATLAB仿真得到此声场的方向特性图,进而分析和比较了能量不同、照射区域大小不同的激光束所激发声场的方向性.研究表明等离子体椭球模型更符合实验情况.     

时间、能量分辨的光电离质谱技术研究气相自由基反应

闪光光解流动管反应器与同步辐射光电离质谱技术两者相结合组成实验平台用于探测气相自由基反应动力学。外触发的脉冲激光光解流动管反应器内的先驱物来产生待反应的自由基;自由基与反应气体发生反应后,由流动管侧壁小孔取样、取样后的混合气体被同步辐射光电离;飞行时间质谱探测光电离产生的离子。同时脉冲信号触发脉冲发生器使其产生一连串的脉冲,间隔40~50μs,此脉冲外触发质谱的采集,连续采集覆盖单次光解反应过程。质谱的时间分辨率为40μs,满足微秒时间内探测反应动力学过程。通过同步辐射光电离反射飞行质谱能直接探测自由基反应产物,并利用光电离效率曲线获得其电离能并区分不同的异构体。实验利用光解产生Cl自由基并与1-丁烯和异丁烯反应,测得反应的加成和消除产物,并获得其加成产物的电离能。     

Absorption coefficients of sulfur dioxide microwave rotational lines

New calculations of the absorption coefficients of the rotational transitions of ³²S¹⁶O₂ are given for all energy levels up to J = 50 and frequencies less than 200 GHz. A spectrometer incorporating a semiconfocal Fabry-Perot resonant cavity and operating in the vicinity of 70 GHz is described. The calculated absorption coefficients are compared to measured values obtained with this spectrometer and to existing measurements over the frequency range 26–40 GHz. The results obtained are in general agreement to within 5–10%. A detailed knowledge of the absorption coefficient behavior as a function of frequency is of particular interest in the development of high-sensitivity SO₂ monitors, and in investigations of the kinetics of fast chemical reactions.     

一种性能稳定的新型频率选择表面及其微带天线应用

设计了一种基于分形树结构的高性能频率选择表面(frequency selective surface,FSS),并将其作为微带天线的空间滤波器,同时改善天线的辐射与散射性能.该FSS单元是由两层金属及其中间介质组成,上、下层金属采用金属柱连结,整体构成树枝状分形结构.通过优化参数,得到了一种宽带、极化无关、宽入射角、小型化的超薄FSS,厚度只有约0.017λ.将该FSS应用于微带天线后,天线的相对带宽拓展到40%,工作频段内的增益得到改善,9.6 GHz时,天线的增益提高了6.7 dB,同时,天线工作频带内的雷达散射截面(radar cross section,RCS)也得到了明显减缩,最大减缩为12.7 dB.实验结果与仿真结果符合得较好,证实了该空间滤波器具有提高宽带天线增益、增强天线定向性、改善天线带宽与降低天线带内RCS的效果,可以应用于宽带天线带内辐射与散射性能的同时改善.     

自由电子激光辐射频谱测量

文章描述了在环形电子束和实心电子束自由电子激光(FEL)研究中,测量辐射频谱使用的两种方法——波导色散线和带通滤波器谱仪。介绍了测量系统的组成和特点,给出了测量结果:环形束FEL试验。辐射频率在27—38GHz内可调:实心束FEL试验,辐射频谱带宽～1.2GHz。     

Design and simulation of nano-antenna with tunable direction of radiation

A new concept for tuning direction of radiation in nano-antenna with negative and positive polarizability is introduced and evaluated by numerical simulation. It has shown that such a configuration consisted of an array of nanoparticles can tune the direction of radiation pattern successfully. Increasing the number of nanoparticles exhibits more directivity at special direction. Variation in position of nanoparticles is used to tune the angle of maximum radiation. The maximum tunability for special geometry of three particles is about 40°. Angle of maximum radiation pattern for four particles is shifted from interval 150–180° to 0–30°.