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为了验证电离层杂波干扰的存在及研究其对高频地波雷达性能的影响,武汉大学电波传播实验室在浙江舟山东沙试验基地利用高频地波雷达完成了电离层杂波干扰识别新试验.试验采取改变地波雷达发射天线结构即改变发射天线的波束指向,使得电磁波垂直向上发射,进行电离层垂直探测试验;同时也有部分能量向海洋传播,从而获得海面Bragg散射回波.与此相对应地采用垂直极化的三元八木天线向海洋表面发射电磁波,同时获取海洋回波与电离层杂波.详细介绍了试验过程并对实测结果进行了初步分析,并介绍了新近研制的便携式高频地波雷达OSMAR-S的系统结构及其工作参数. 相似文献
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为了实现天线收发共用,设计了一种大功率短波宽带收发开关,它主要用于高频雷达和大功率短波通信系统.从提高隔离度的角度提出了以对称式双PIN二极管为核心的开关电路,为了减少收发开关的转换时间、降低功耗和提高其稳定性,提出了单极性脉冲电路作为开关电路的控制脉冲电路,同时提出了接收机和发射机保护电路.在便携式高频地波雷达系统中,单极子/交叉环天线通过大功率短波收发开关实现了一发三收收发共用,简化了便携式高频地波雷达的天线系统,减少了天线的占地面积,同时降低了天线架设的难度,本系统硬件电路简洁,功耗低,工作稳定、可靠. 相似文献
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武汉大学高频地波雷达课题组经过 2年多的艰苦努力 ,自行研制了两台高频地波雷达OSMAR2 0 0 0 .完成了国家 86 3计划海洋领域的重大项目“高频地波雷达海洋环境监测技术”的研究项目 ,于 2 0 0 0年底通过国家科技部的验收 .该项目研制的高频地波雷达OSMAR 2 0 0 0采用一发八收相控天线 ,在中国大陆沿海首次实现双站岸基雷达监测海洋表面动力学参数 ,得到了海洋表面矢量流图 .与传统海洋测量仪器的对比验证试验表明 ,OSMAR2 0 0 0探测海流和海面风向的距离超过2 0 0公里 ,探测浪高的距离达 15 0公里 .其整体性能已达到国外同… 相似文献
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本文通过顶部加载多个平面阿基米德螺旋线圈得到具有多频功能的电小地波雷达天线。采用CST软件设计多个平面螺旋线圈的尺寸参数,所设计的天线具有3.7 MHz、6.5 MHz和8 MHz三个频点,天线总高度相对3.7 MHz的天线电长度仅为0.077λ,属于电小天线。采用Dixon优化算法实现多频点的阻抗匹配,在匹配元件数较少前提下保证各个频点带宽大于60 kHz,满足了设计要求。天线实测结果和CST仿真结果吻合,说明了本文方法在实现高频地波雷达天线小型化和多频化方面具有可行性和有效性。 相似文献
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相控阵天线辐射单元的互耦特性对天线整体性能有着重要影响,而互耦与具体单元形式相关,因此模型复杂,
难以精确计算和预测。在阵元的小型阵列试验过程中,采用互耦测试的方法,对准八木振子、微带贴片、Vivaldi 单元
等几种典型宽带相控阵单元的互耦特性进行了实验研究,结果表明互耦对不同类型的单元影响大不相同,对单元特性
不仅有传统认为的负面作用,还可能有改善性能的作用,分析结果可供相控阵天线设计时参考;同时,利用测试数据
分析了小型试验阵列的规模对结果的影响,提出了小型阵列的规模依据。 相似文献
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Boyd D. Colin Lawrence Peter D. Bratty Paul J. A. 《IEEE transactions on bio-medical engineering》1978,(3):236-243
A model has been proposed for the generation of single motor unit potentials routinely observed in the clinical EMG examination of the normal biceps brachii muscle. A dipole representation was chosen for the single fiber activity. The motor unit was constructed from a uniform random array of single fibers. Motor unit potentials generated by this array have been observed at various distances both inside and outside the array. The effects of single fiber dipole axial dispersions on the potentials observed at increasing distances from the array have also been investigated. Motor unit potentials generated by the model have been compared with existing data from multielectrode studies in the biceps brachii. 相似文献
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针对目前雷达功能单一,品种较多,提升雷达功能需要更换大部分硬件(尤其天线系统)的问题,提出一种通过天线配置实现软件定义雷达的开放式系统架构。该架构的发射信号基于阵列单元通过软件任意产生,天线可按系统功能通过软件编码控制任意裁剪且可重构。天线单元阵列射频端直接连接二相编码调制器,通过正交二相编码调制,突破了单通道任意数字波束形成,解决了通道一致性问题,使得天线配置更加灵活。该架构不仅可应用于常规相控阵雷达, 还可应用于 MIMO、认知、雷达通信一体化等。通过软件定义开发的多路复用数字波束雷达系统平台,已经完成实际外场测试,表明基于软件定义的多路复用数字波束相控阵雷达技术系统应用可行。 相似文献
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《Electron Devices, IEEE Transactions on》1985,32(8):1402-1406
A new field integration frequency interleaving color-television pickup system has been developed for a single-chip CCD color video camera. This system uses anew color filter array, comprising a plurality of unit filter arrays, each unit consisting of 2 × 4 filter elements of yellow, cyan, and green color. High color fidelity and high-resolution color pictures without frame integration lag were obtained using only a ½-inch interline transfer CCD having 500 × 400 picture elements. 相似文献
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In this paper we describe a TSPC (True Single-Phase-Clock) barrel shifter for high-speed, real time applications. The circuit consists of a shift and rotate array and a control unit, both having a pipeline structure, which allows on-line programming. Using 1.5 μm CMOS technology, a full custom prototype for 16-b data shift and rotate array has been implemented, with a simplified control unit, and testing circuitry. Worst case HSPICE simulations indicate a maximum operating frequency of over 100 MHz, both for the barrel with on-line programming and for the barrel implemented. The full functionality of the prototype has been tested up to 25 MHz, although each bit path has been tested at 100 MHz 相似文献
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Ohta J. Nitta Y. Tai S. Takahashi M. Kyuma K. 《Lightwave Technology, Journal of》1991,9(12):1747-1754
A novel type of photodetector called a variable sensitivity photodetector (VSPD) has been developed for an optical implementation of a neural network. The function of the VSPD is a photodetector with functions of both a spatial light modulator and a photodetector. The VSPD with a metal-semiconductor-metal structure is shown to be suitable for the implementation of the analog synaptic weight with a bipolar value. A two-dimensional 8×8 array of VSPDs was fabricated on a GaAs substrate and integrated with a light-emitting-diode array with eight lines in hybrid form. This chip can simulate an eight-neuron system with 64 variable synaptic connections. The application to pattern classification was demonstrated by using the chip. The chip was used to classify 12 patterns into three categories by the backpropagation learning algorithm in a three-layered network. The authors studied how the nonlinear and nonuniform characteristics of the VSPD array device affect the learning performance 相似文献