中低轨卫星多普勒数据处理技术研究

分析了中低轨卫星多普勒频率模型特性,采用数据拟合法对多普勒数据进行处理,有效抑制随机误差。仿真结果表明,经过处理后的观测数据精度得到了明显提高。     

Analysis of digital spectral processing of laser Doppler vibration meter signals

A digital spectral method of the maximum harmonic for processing laser Doppler vibration meter signals from a surface vibrating according to a harmonic rule is analyzed. A digital model for this signal in the presence of additive and multiplicative noises is suggested. Examples are given for the effect of signal discretization frequency on the error of determining vibration amplitude. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 42–45, September, 2006.     

一种推导黑体温度变换的简易新方法

近一个世纪以来,对黑体相对论温度变换的讨论一直在进行着。其中最具代表性的变换是在上世纪六十年代,由R.N.Bracewell等人以从实验发现的3K宇宙背景辐射为基础、从与实验符合很好的Plank黑体辐射公式出发,用不同方法得到的变换式T=T0     

Removal of bird-contaminated wind profiler data based on neural networks

This paper presents the results of a study that relied on trainable neural network classifiers to identify and remove bird-contaminated data from wind measurements recorded by a 1290-MHz wind profiler. A wind profiler is a Doppler radar system measuring the three-dimensional wind field. Migrating birds crossing the radar beam can lead to erroneous wind observations. Bird removal was performed by training conventional feedforward neural networks (FFNNs) and quantum neural networks (QNNs) to identify and remove bird-contaminated data recorded by a 1290-MHz wind profiler. A series of experiments evaluated several sets of input features extracted from wind profiler data, various FFNNs and QNNs of different sizes, and criteria employed for identifying birds in wind profiler data.     

Measurement of flow in small vessels by magnetic resonance phase mapping techniques: anin vitro andin vivo study

The measurement of blood flow in small arteries is a potential extension of magnetic resonance (MR) angiography. We have compared flow measurements based on MR phase mapping with those obtained by Doppler ultrasound and electromagnetic flowmetry in both phantom and animal models. Correlation between modalities was high forin vitro studies (R ²=0.93–0.98).In vivo, electrocardiogram-gated MR and Doppler ultrasound flow measurements compared to electromagnetic flowmetry showed fair correlation coefficients (R ²=0.73 and 0.66, respectively). However, limits of agreement indicated that in small vessels flow measured by the three modalities could differ by up to ±90 mL/min. For both models, arteries in the range of 3–6.5 mm in diameter produced complementary errors in area and velocity measurements in MR studies. Ungated MR studies showed a reduced agreement (R ²=0.88in vitro, 0.54in vivo), which may in part be due to poor sampling of the velocity pattern. The results show that the high correlation obtainedin vitro cannot be extrapolated to thein vivo situation, where additional physiological and anatomical variables are encountered.     

A Method of Taking into Account the Effect of Fluctuation Modulation of the Reflected Signal on the Accuracy of a Single-Pulse Direction Finder

A method of taking into account the fluctuation modulation of the reflected signal is proposed. This modulation leads to power losses in the functional processing of the signal in the channel of a single-pulsed direction finder. An algorithm of the functioning of a single-pulse direction finder with long-term coherent storage which eliminates these power losses is developed.     

基于5G波段的V2V高速无线信道建模

高速移动的车车(Vehicle-to-Vehicle,V2V)信道与传统蜂窝系统的无线信道相比,其不同在于V2V无线信道的快速时变特性,主要体现在多径分量的快速变化、存在较大多普勒频移以及每条多径都具有动态生/灭特性。提出了一种高速无线信道建模方法,采用马尔科夫链模拟信道的动态生/灭特性,基于Nakagami分布仿真莱斯、瑞利等信道单径衰落,用抽头延时线模型完成高速多径信道建模。与传统无线信道建模方式相比,具有快速建模、动态改变和易于产生的特点,为高速移动无线接收机算法的开发奠定了基础。仿真结果表明,城市车内天线(UIC)信道多径数目最多,衰落最严重。     

基于多普勒测速的水下传感器时间同步算法

时间同步是水下传感器网络的关键技术,由于海洋中采用水声通信时传播时延高且存在多普勒频移,导致使用射频通信的陆上时间同步算法无法直接应用于水下环境.基于多普勒测速原理和节点在水下的移动性,提出一种新型的时间同步CD-Sync算法.利用具有聚类特性的分簇模型选择合理的簇首节点,并与水面信标节点进行簇内同步,且在同步过程中,...     

大频移低信噪比下长PN码快速捕获及其DSP实现

针对卫星导航定位系统中大多普勒低信噪比下长PN码快速捕获的难点，提出一种时频二维联合搜索快速捕获的改进方法，采用了合理的捕获策略和频域循环移位的多通道软切换，简化了捕获处理，利用多相结构的码相位搜索，降低了运算复杂度。该方法在TI公司TMS320C6416为核心器件的硬件平台上实现，仿真和实验结果表明其具有很好的捕获性能。