共查询到20条相似文献,搜索用时 15 毫秒
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The successful use of embedded resistors in many applications will require that the fabricated resistors be trimmed prior to lamination into printed circuit boards to attain required design tolerances. Depending on the application, the economic value of the board being fabricated, and the process used to create the embedded resistors, it may also be prudent to consider reworking resistors that are incorrectly trimmed or with initial values that are too large (untrimmable resistors). This paper uses a model of the resistor/board yield coupled with a cost model of the trim and rework processes to identify conditions under which applications should neither trim nor rework, trim but not rework, or perform both trimming and rework of embedded resistors, as a function of the design tolerance for the resistors and the accuracy with which the embedded resistors can be fabricated. Example results are presented for several applications ranging from small boards with a high density of embedded resistors to large boards with a low density of embedded resistors. Distinct regions of trimming and rework applicability that are nearly application independent can be identified as a function of design tolerance, printing/plating/etching variation, and the characteristics of the trimming process. 相似文献
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In this letter, we describe a simple method to adjust the oscillation wavelength of distributed-feedback (DFB) lasers after the device fabrication without using any external active tuning. The method utilizes a permanent change of refractive index in the quantum well active layer induced by external laser beam irradiation. We have demonstrated 0.36 nm adjustment in a 1.55-/spl mu/m ridge waveguide DFB laser. 相似文献
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《Mechatronics》2003,13(6):533-551
This paper describes a position-based visual servoing system for edge trimming of fabric embroideries by laser. The high-speed vision system, based on a 220 Hz digital camera and the TMS320C40 parallel DSP processor is presented, and the novel image processing algorithm developed for seam tracking applications is briefly explained. Two methods for seam trajectory generation are discussed. In the first method the tracking trajectory is determined only by using the vision data; in the second method, which is suitable for periodic patterns, the predetermined path data is modified by the vision data. A tracking controller using a feedforward controller in the tangential direction of the seam and a feedback controller in the normal direction is described. The custom built manipulator is a four-axis velocity controlled gantry robot with independent PID controllers for each axis. The axes’ reference speeds are commanded and updated by the top-level tracking controller in equal time intervals. The gantry controller program runs on a Pentium PC. The experimental results in edge trimming of different seam patterns are presented. 相似文献
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The speed limitations imposed on the laser trimming of active networks by trim-induced transients are discussed. It is predicted that for a majority of cases these transients rather than the measurement system will become the major speed limitation of the trimming process. 相似文献
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A laser trimming technique in which a finite number of links are cut in a regular mesh of identical-valued resistors is described. The method eliminates long-term resistance drift due to slow annealing in the `heat-affected-zone' adjacent to the laser kerf. It is shown that the precision and resolution can be comparable to those achieved with conventional methods, and that quite wide ranges (up to 4:1) of absolute values can be obtained with small meshes. A computational method for constructing a lookup table of resistor values for different cut patterns is described 相似文献
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对普通照相所拍摄的彩色景物光栅编码黑白照片作一次单色激光全息曝光记录就得到景物的二维真彩色全息图。与一般的三次曝光法相比,本方法减少了对散射光的记录次数,提高了信噪比,可得到更清晰的全息像。记录中曝光次数的减少也提高了全息图的衍射效率,使再现像更明亮。最后,对图像的三基色信息的同时记录可使再现像颜色更趋于与原景物颜色一致。 相似文献
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简要地介绍了机载激光武器的使命和研制进展,分析了作战信息链及其先进的红外搜索与跟踪传感器、跟踪照明激光器和超灵敏的弱光探测器。最后,讨论了武器系统的作战时序。 相似文献
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Linearization of DFB laser diode by external light-injected cross-gain modulation for radio-over-fiber link 总被引:2,自引:0,他引:2
Sang-Hoon Lee Jeung-Mo Kang In-Hyuk Choi Sang-Kook Han 《Photonics Technology Letters, IEEE》2006,18(14):1545-1547
A novel linearization technique of distributed-feedback laser diode in analog optical transmitter for radio-over-fiber (RoF) link was proposed. The proposed scheme was based on a light-injection technique using cross-gain modulation effect. According to the proposed idea, a linearized RoF transmitter module was implemented and evaluated. The enhanced performance of carrier-to-noise ratio and spurious-free dynamic range were experimentally demonstrated in a wide range of radio-frequency (RF) applications. The experimental results show that the proposed scheme can be applicable for broadband RF optical transmission applications. 相似文献
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在星间数据交换过程中,同时传输不同类型的数据会对系统性能产生较大影响。为统一传输制式,提高数据传输效率,提出星间激光链路接口模型。在星间激光链路接口模型中,针对节点卫星数据处理转发效率低的问题,设计数据帧调整单元整合不同信源的数据;针对空间信道随机错误对系统性能影响较大的问题,添加链路传输处理单元提高激光链路传输的可靠性。研究了星间激光链路接口模型在中继卫星系统与分布式卫星系统中的实现方法。结果表明,采用星间激光链路接口模型后系统传输效率提升了49.93%,纠错性能提升了3.01 dB。 相似文献
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激光横向切割长度对片式电阻阻值影响的实验研究 总被引:1,自引:0,他引:1
激光在片式电阻上的横向切割长度对阻值影响较大 ,合理设计其长度能够以较低成本提高激光调阻精度及调阻效率。通过实验数据分析得出激光横向切割的长度变化率与阻值变化率之间的定量结论 ,并拟合了有效横向切割长度的阻值变化率与切割长度变化率之间的关系函数 ,二者能够为提高调阻精度和调阻效率提供控制依据。 相似文献
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Deluca P. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2002,90(10):1614-1619
As devices and circuits become smaller and more complex, constant innovation is required from capital equipment suppliers. This is true in all of the ever-expanding applications of electronics including computers, telecommunications equipment, automobiles, and instruments. Lasers, usually focused down to micrometer-sized spots of energy, have become the fundamental tool for physically micromachining or exposing a wide variety of materials. Applications now range from printed circuit boards and hybrid circuits down to semiconductor devices. The following paper describes how computer-controlled work-cells based around the ubiquitous laser or laser systems, as they are called in the electronics industry, have changed the way all electronics products are manufactured. 相似文献
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M. Arrigoni R. Madd 《International Journal of Satellite Communications and Networking》1988,6(2):197-207
Following a brief introduction reviewing various laser systems suitable for ISL, a typical link budget for an optical ISL with a Nd laser is calculated. Laser diode pumped Nd lasers are described, and several host materials are considered. Modulation formats and typical receiver performances for direct detection are examined in order to compute the minimum transmitted power required for the proposed link. Results show that laser diode pumped Nd laser systems are competitive for optical ISL. 相似文献
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星地激光链路中的光信号快速识别方法 总被引:2,自引:2,他引:0
依据图像传感器探测背景光的噪声情况,定义了光背景特征值,用其来描述星地链路光背景噪声对于卫星光通信的瞄准、捕获和跟踪的影响.在星地链路光背景噪声条件下,对光信号识别和捕获的影响进行了分析,同时,提出了捕获光点路径优化算法,根据此算法可以得到星地激光链路区域光背景噪声的特征规律,并阐述了光背景噪声情况下的光信号快速识别方法.经模拟实验分析表明:该算法能够在光背景噪声情况下对光信号进行快速识别和捕获,满足了图像实时处理要求,增强了图像处理系统的抗干扰能力,因此,对星地激光通信具有一定的参考意义. 相似文献
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Yu-Huang Lin Gong-Ru Lin 《Photonics Technology Letters, IEEE》2004,16(8):1819-1821
We report a mutually injection-locked erbium-doped fiber amplifier (or laser) and Fabry-Pe/spl acute/rot laser diode link (EDFA-FPLD or EDFL-FPLD) for single longitudinal mode lasing with linewidth of 0.012 nm and sidemode suppression ratio of 42 dB. The 3-dB linewidths of <20 MHz and 350 kHz for the EDFL-FPLD and EDFA-FPLD links, respectively, are reported using interferometric determination. The mode-beating noise can be completely eliminated in the EDFA-FPLD link. 相似文献
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针对收发口径固有位置偏差对城市近距离激光通信系统的影响进行了分析,建立了链路能量与固有位置误差模型,计算了不同误差下的链路能量情况,并分析了二者关系。以固有位置误差15 mm为例,计算了不同距离下的链路能量,在基础上,进行了实际的通信验证试验,给出具体试验操作流程,并得到了距离10~40 m的实测数据。实验数据表明,与理论偏差不超过0.52 dB,验证了理论能量模型的正确性。该能量模型可用于指导近距离通信端机的设计和链路搭建,同时,小型化光端机的成功研制及通信试验可有效加速城市间近距离下的民用通信领域应用。 相似文献