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制备了基于超导铝膜的四分之一波长反射型共面波导谐振器,并利用矢量网络分析仪测量了该谐振器在低温超导状态下的传输特性。实验结果表明:对于拥有较大耦合电容的超导共面波导谐振器,在超导状态下随着环境温度的升高,超导薄膜的表面阻抗会增大,进而谐振器的中心谐振频率降低,谐振峰变宽。温度越高,谐振频率随温度升高而向低频偏移的速率越快。另一方面,随着环境温度升高,谐振器的外部耦合品质因数和负载品质因数也都会降低。温度越高,谐振器品质因数随温度升高而降低的速率越快。用二能级理论解释了实验现象,品质因数理论计算值与实验测量结果相接近。 相似文献
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提出了一种基于交指电容裂环谐振器的差分微波传感器。通过把交指电容结构嵌入到裂环谐振器的开口处以增强电场束缚效应,并且为了抑制外界环境因素的干扰,制作成差分结构。差分结构采用两个裂环谐振器分别分布于单根微带线两边的结构形式,谐振器与微带线呈磁耦合效应。该传感器结构可以克服传统微波传感器的低灵敏度和易受外界干扰的问题。在实验中,将一个谐振器作为参考单元,另一个谐振器作为测量单元,待检测液体样本放置于测量交指电容处,随着不同浓度的乙醇-水混合溶液的注入,测量单元的谐振频率相较于参考单元会发生明显的频率偏移和陷波幅值的偏差,由此可以拟合出复数介电常数与它们之间的关系以预测不同浓度的乙醇-水混合溶液的复数介电常数值。实验结果表明:所提出传感器的单位体积平均灵敏度可达3.630 8%/μL,比同类型的传感器提高了几倍至几十倍。 相似文献
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设计了一种可调谐频率的高功率宽谱微波辐射装置,装置由可调谐长度的1/4波长低阻同轴谐振器、环形开关、电容耦合器和宽谱辐射天线组成,中心频率调谐为200~400 MHz。低阻传输线与环形开关构成1/4波长短路谐振器,它产生的宽谱微波振荡通过耦合器耦合到宽谱辐射天线上辐射,而耦合器由集中电容与分布电感组成,实现宽谱微波在频率调谐范围内以较为一致的耦合度提取微波能量。通过转动螺杆滑动安装在同轴谐振器内芯上的环形开关,达到改变谐振频率的目的。最后,将可调频宽谱辐射装置与输出电压为500 kV的Tesla变压器脉冲功率源联试,得到200~400 MHz宽谱微波辐射,辐射因子为95~130 kV,频谱百分比带宽为10%~30%。 相似文献
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本文提出了一种新型H型环带谐振器,具有结构紧凑,尺寸小,Q值高,非相邻耦合弱等优点.该谐振器在一侧设置了一个开口,改变开口位置,可以在较大范围内改变谐振器谐振频率,并且能够改变基频和二倍谐频之间的频率间隔.对于直连型馈线引入方式,H型环带谐振器容易实现外部Q值的匹配,同时对输入/输出端谐振器的谐振频率影响很小.本文还基于H型环带谐振器,采用2英寸双面YBCO高温超导薄膜设计并制作了用于CDMA移动通信系统的12节高温超导滤波器.该滤波器的中心频率为832MHz,相对带宽为1.6%.在70K温度下的测试结果显示滤波器的带内插入损耗低于0.28dB,反射损耗优于-15.5dB,带外抑制约为75dB,通带低频端带边陡峭度超过30dB/MHz,高频端带边陡峭度超过20dB/MHz. 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
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A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users. 相似文献
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A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
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A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle's expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance. 相似文献
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Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use. 相似文献
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References: 《声学学报:英文版》2008,27(1):23-33
The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results. 相似文献
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The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献