共查询到19条相似文献,搜索用时 156 毫秒
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随着遥感技术的飞速发展,遥感数据的传输速率和编码性能要求越来越高。在高码速率、复杂编码的条件下,设计符合国际空间数据系统咨询委员会(CCSDS)标准的高码速率解调器成为解决遥感卫星数据解调的关键。在软件无线电平台的解调器结构下,分析低密度奇偶校验码(LDPC)译码特点,完成译码模块结构、解调速率、存储规则的设计。设计结果满足高码速率遥感卫星解调器要求,提高了数据的下传效率和空间资源的利用效率。 相似文献
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精细调节卫星接收天线的极化隔离 总被引:1,自引:1,他引:0
1精细调节卫星接收天、馈线系统极化隔离的重要性目前 ,电视卫星的轨道资源和频率资源已经显得十分紧张 ,随着转发节目套数的增加 ,正交极化频率复用 ,即在同一卫星上使用同频率 (或频率相近 )正交极化转发不同节目已很普遍。图1是亚太1A卫星C波段转发器的频道设置。正交极化频率复用 ,节目的分离是靠系统的极化隔离度来保证的。但是 ,受加工精度的限制 ,把接收天、馈系统的极化隔离度做得更好十分困难。而在安装、调试过程中 ,隔离度损失一些 ,往往又被忽视。近来 ,我们发现 ,由于极化隔离调节不好 ,在接收同频正交极化节目时 ,常常出… 相似文献
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随着对地观测技术的快速发展,遥感卫星空间分辨力的不断提高,星地链路传输的信息量越来越大,码速率越来越高,数据传输频段已经由传统的X频段扩展到Ka频段,以满足海量遥感数据传输的需求。但Ka频段低轨遥感卫星波束非常窄,遥感卫星地面接收系统需要具备良好的跟踪性能,才能实现系统稳定的捕获跟踪,保证接收数据的质量。文中通过对跟踪方式和跟踪精确度方面进行分析和论证,优化捕获跟踪流程,实现对低轨遥感卫星Ka频段的捕获跟踪。文中提出利用S频段跟踪引导Ka频段跟踪的方式,高低仰角采用不同的优化流程设计,结合高分辨力对地观测系统重大专项的先期研究内容和某地面接收站进行了设计验证,结果表明,可实现低轨遥感卫星Ka频段的捕获跟踪,待时机成熟,可进行工程应用。 相似文献
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本文论述了影响馈源极化性能的四个主要因素,通过对这些因素的分析,提出了具有高极化性能的频率复用网络的设计方法,给出了一个可双圆双线极化工作的实际网络的测试性能。 相似文献
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遥感卫星地面接收系统包括天伺馈系统、跟踪接收信道分系统、数据记录处理和快视分系统、遥测遥控分系统、任务管理分系统、测试标校分系统。在对接收系统进行方案设计时 ,应针对不同遥感卫星的轨道、数据速率、成像方式等 ,重点解决多星适应性、卫星过顶跟踪、双通道实时合成及快速反应等关键技术 ,并对系统主要指标进行计算。介绍了遥感卫星地面接收系统总体设计的方案、关键技术及解决途径、系统主要指标的计算方法 相似文献
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基于自适应编码调制的遥感数据传输方案实现了传输速率阶梯式换挡,但未能充分利用链路余量。为进一步提高遥感卫星数据传输过程中的频谱效率,提出了基于无速率码的遥感数据自适应传输技术。将无速率码与QPSK、8PSK、16QAM、64QAM调制方式结合,通过设定译码成功概率阈值得到离散信噪比下的最佳译码开销和最佳码率值。采用多项式拟合求得卫星过境期间码率值的变化情况,进而得到有效数据率变化曲线,实现了遥感卫星过境时段内有效数据率随仰角的无缝切换。通过求解有效数据率曲线的积分值,得到了采用联合译码算法的Raptor码在4种方案下的传输数据量。分析结果表明,与第二代数字卫星电视广播标准(DVB-S2)中的自适应编码调制方案相比,所提出的传输方案使传输数据量提高了10.29%~27.65%,且在信噪比低至-5 dB的情况下也可以进行数据自适应传输。 相似文献
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X/Ka频段遥感卫星地面接收信道便携式测试系统设计 总被引:1,自引:0,他引:1
为解决X/Ka信道在建设和运行维护过程中测试设备笨重、功能单一、设备操作复杂、工作状态无法获取等弊端,通过优化中频与射频链路方案、小型化与多功能集成设计、集中监控与射频线缆供电等方式,设计了一种便携式X/Ka频段遥感卫星接收信道测试系统,实现了1 GHz宽带X/Ka卫星数据地面接收系统射频(7.9~8.9 GHz、18~20 GHz、25~27.5 GHz 3个频段,有线或无线)、中频环路的调试和测试(1.2 GHz、1.5 GHz 2个频段)及信道的测试系统的集中监控、高阶调制、多种编码、多普勒仿真、噪声源添加等功能,极大地方便了现场或野外测试应用。 相似文献
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Zoltn Katona Michael Grßlin Anton Donner Norman Kranich Hartmut Brandt Hermann Bischl Martin Brück 《International Journal of Satellite Communications and Networking》2020,38(3):301-313
From a geostationary Earth orbit (GEO) satellite's perspective, a low Earth orbit (LEO) satellite is visible on more than half of its orbit. Albeit the free‐space loss of an inter‐satellite link is much higher than the one of a direct ground link, considerable data rates and download volumes can be achieved. In this paper, we describe the system architecture of an integrated approach for a data relay satellite system and the development of LEO satellite and ground station modems. The approach allows serving several small and inexpensive LEO satellites at the same time both with low rate telemetry/telecommand links and with high rate download of sensor data. 相似文献
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Dual-polarized operation of satellite communications channels allows for an efficient use of the radio spectrum. A method for evaluating the availability of Ku- and Ka-band dual-polarized digital systems is described. It is based on long-term measurements of slant-path attenuation and depolarization caused by the troposphere and of their joint occurrence. The additional degradation of dual-polarized system availability performance with respect to single polarization operation is assessed, and its dependence on major link and system parameters is highlighted. It appears that satellite links characterized by high-frequency, low elevation angle, circular polarization, and high-level modulation schemes are particularly affected by the depolarization-induced interference. In that case, doubling their capacity by dual-polarization frequency reuse reduces dramatically their availability, assuming a fixed link margin, or alternatively requires prohibitive link margins to meet a given availability objective 相似文献
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Shasha Zhang Haiyi Cao Xinwei Zhang Xinyu Yao Chenguang Zhao 《International Journal of Satellite Communications and Networking》2020,38(5):437-449
In order to make full use of the link resources for data transmission from near‐earth remote sensing satellites, variable coding modulation (VCM) system is used to fully utilize the system link margin to improve the satellite data transmission performance. By analyzing the dynamic link under the VCM data transmission system, the contribution of the VCM system to the satellite data link optimization is studied from the perspective of engineering application, which can provide reference for the data link design of remote sensing satellites. Applying the flow design, for the currently adopted transmission system of X band, compared with traditional constant coding modulation (CCM) system, the average link performance of VCM system can be increased by 42.1% in single‐station transmission mode and 53.3% in dual‐station relay mode through the exampled analysis. 相似文献
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T. D. Kritikos A. D. Panagopoulos J. D. Kanellopoulos 《International Journal of Satellite Communications and Networking》2011,29(2):143-161
Atmospheric impairments have a significant influence on the performance of modern satellite communication networks, working at Ku, Ka and potentially Q/V frequency bands. Both differential rain attenuation from an adjacent satellite system, operating at the same frequency range, and cross‐polarization phenomena on dual polarized satellite systems due to rain and ice crystals, induce a further aggravation on the already limited signal‐to‐noise‐plus‐total‐interference ratio (CNIDR), due to the frequency and orbital congestion of today's global communication satellite constellation. In the present paper, a new statistical methodology, towards the modelling of CNIDR under rain fade conditions, is proposed to include interference effects by two adjacent satellites, incorporating the impact of correlated fading channels (spatial rainfall inhomogeneity) of multiple slant paths. The method is based on a convective raincell model and the lognormal assumption for both the point rain‐rate statistics and the slant‐path rain attenuation. The obtained numerical results indicate the significant impact of the second interfering satellite on the aggravation of total interference effects. Some simple mathematical formulas for the prediction of the CNIDR, based on the derived theoretical results, and demonstrating the influence of various link parameters on the total link availability statistics, are also presented. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献