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排序方式: 共有612条查询结果,搜索用时 78 毫秒
91.
在处理全球卫星导航系统(Global Navigation Satellite System,GNSS)卫星信号时,针对模数转换器(Analog-to-Digital Converter,ADC)量化位数不同导致输出的信号信噪比下降的问题,推导了阵列天线波束形成后输出信号的信噪比理论计算模型,分析了ADC量化位数对阵列天线抗干扰GNSS接收机的性能影响。在7阵元天线且ADC量化位数为10的条件下,理论模型分析和数据仿真结果表明最大抗干扰能力约为85 dB。通过确定ADC量化位数与抗干扰GNSS接收机抗干扰能力之间的关系,其结论为工程应用中抗干扰GNSS接收机的ADC选型和设计提供了理论依据。 相似文献
92.
面向全球导航卫星系统(Global Navigation Satellite System,GNSS)信号的外辐射源雷达,是一种利用环境中GNSS信号作为非合作照射源进行探测的雷达。为满足基于GNSS信号的外辐射源雷达系统仿真和信号处理算法设计评估的需要,通过对该雷达系统组成与工作原理的分析,完成了面向GNSS信号的外辐射源雷达软件化信号模拟器的设计与实现。给定仿真场景下软件化模拟器输出信号处理和分析的结果验证了该模拟器可根据输入参数与模型正确完成信号仿真。 相似文献
93.
对于卫星移动通信系统,由于卫星与地面终端之间的相对运动以及星地间传输延迟,传统的基于理想信道信息的预编码方法是不适用的。针对这一问题,提出了一种基于开环信道估计的预编码方法。卫星端利用开环获取的部分信道信息实现多波束联合预编码,并导出了系统传输速率的闭合解析表达式。此外,为了克服强干扰环境下多波束预编码系统性能恶化问题,提出了一种自适应预编码传输方法。卫星发射机依据开环获得的慢时变用户位置信道信息和信道统计量信息,自适应地选择预编码方法或传统频率复用方法,实现最优的系统性能。理论分析和仿真结果表明,与传统的干扰抑制方法相比,所提方法能实现更优的系统性能,同时也克服了传统预编码方法的局限性。 相似文献
94.
在性能、成本和可靠性的多重约束下,采用商用货架(Commercial Off-The-Shelf,COTS)器件设计了一种高性能、低成本星载收发信机。该收发信机的硬件设计不但可同时满足星地和星间应用需要,而且还具有支持多波束、多信道接入的特点。软件设计主要解决了大多普勒频偏条件下的低信噪比解调和变长以太网数据帧的高效处理等问题。地面测试结果表明,在250 kb/s ~ 14 Mb/s信息速率范围内,误比特率低于1.0×10-6时所需的解调信噪比(Eb/N0)不超过2.8 dB,发射信号误差矢量幅度不超过1.9%,高速应用时处理时延可低至3.0 ms。为降低COTS收发信机的可靠性风险,分别在元器件、电路和系统层面进行了有针对性的可靠性保证措施。该设计经过了在轨测试的验证,对其他低轨商业通信载荷的研制有一定的参考价值。 相似文献
95.
Jens Rommel Daniel Hermann Malte Müller Oliver Mußhoff 《Journal of Agricultural Economics》2019,70(2):408-425
Recent studies cast doubt on the ability of abstract experiments to predict decision‐making in the field. Thus, scholars have argued for more ‘realism’ by introducing context to field experiments. Yet, such realism may work against the induced values of monetary incentives in economic experiments. It is an open question whether contextual framing works best with or without inducing values, through methods such as the use of monetary incentives. Using a sample of 146 German farmers, we compare experimentally the predictive power of a framed lottery in an agricultural context vs. using an abstract version. For one half of the sample, lotteries are incentivised; for the other half, they are hypothetical. Although risk preferences differ between treatments, all four lottery tasks correlate poorly with farmers’ real‐world use of risk management instruments such as harvest or hail insurance. Subjects who start with an agricultural framing are willing to take significantly greater risks in the lotteries. More generally, our findings cast doubt on the ability of lottery tasks to predict risk‐taking in the field. 相似文献
96.
97.
《Food Policy》2019
Base of the Pyramid (BoP) consumers living in the urban informal settlements of developing countries spend over 60% of their income on food, yet malnutrition and micronutrient deficiency remain widespread among these populations, pointing to the inadequacy of the foods they consume in terms of quality and quantity. In this paper we examine BoP consumers’ willingness to pay (WTP) for nutritious multi-composite porridge flour (improved flour) in the informal settlements of East Africa. The analysis is based on experimental data collected from 600 households in the informal settlements of Kampala, Uganda and Nairobi, Kenya (300 in each country) in 2016. We use Tobit regression models to analyse determinants of WTP for the improved porridge flour. Results show that both Kenyan and Ugandan BoP consumers are willing to pay a premium for the improved porridge flour. In addition, providing nutrition information about the flour, characteristics of household head, economic status of the household, and presence of young children between six and 59 months in the household, influence WTP for the safe and nutritious porridge flour. The paper concludes by providing recommendations for enhancing nutrition among poor consumers in the informal settlements of developing countries. 相似文献
98.
99.
We use an experimental survey design to measure how campaign finance regulation influences perceptions of political corruption and trust in politicians when citizens are exposed to information about regulation. Unlike most observational studies, results of this experimental study suggest that knowledge of campaign finance regulation substantially reduces citizens’ perceptions of corruption but has only limited effect on trust in politicians. Findings have crucial implications for public policy. At a time when public cynicism about politics is high, a significant reduction in perceptions of political corruption through successful dissemination of campaign finance regulation would be a boost to the legitimacy of democracies. 相似文献
100.