High-Precision Doppler Frequency Estimation Based Positioning Using OTFS Modulations by Red and Blue Frequency Shift Discriminator

Orthogonal Time Frequency and Space(OTFS) modulation is expected to provide high-speed and ultra-reliable communications for emerging mobile applications, including low-orbit satellite communications. Using the Doppler frequency for positioning is a promising research direction on communication and navigation integration. To tackle the high Doppler frequency and low signal-to-noise ratio(SNR) in satellite communication, this paper proposes a Red and Blue Frequency Shift Discriminator(RBFSD) based on the pseudo-noise(PN) sequence.The paper derives that the cross-correlation function on the Doppler domain exhibits the characteristic of a Sinc function. Therefore, it applies modulation onto the Delay-Doppler domain using PN sequence and adjusts Doppler frequency estimation by red-shifting or blue-shifting. Simulation results show that the performance of Doppler frequency estimation is close to the Cramér-Rao Lower Bound when the SNR is greater than -15dB. The proposed algorithm is about 1/D times less complex than the existing PN pilot sequence algorithm, where D is the resolution of the fractional Doppler.

Research of Frequency Discriminator on Frequency Lock Loops

Frequency lock loops （FLL） discriminating algorithms for direct-sequence spread-spectrum are discussed. The existing algorithms can＇t solve the problem of data bit reversal during one pre-detection integral period. And when the initial frequency offset is large, the frequency discriminator can＇ t work normally. To solve these problems, a new FLL discriminating algorithm is introduced. The least-squares discriminator is used in this new algorithm. As the least-squares discriminator has a short process unit period, the correspond- ing frequency discriminating range is large. And the data bit reversal just influence one process unit period, so the least-squares discriminated result will not be affected. Compared with traditional frequency discriminator, the least-squares algorithm can effectively solve the problem of data bit reversal and can endure larger initial frequency offset.

Analysis of single frequency modulation for passive hydrogen maser

Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated. Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation. The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.

基于特征融合和B-SVM的鸟鸣声识别算法

为了实现在野外通过低成本嵌入式系统识别鸟类,提出了基于特征融合和B-SVM的鸟鸣声识别方法。对鸟鸣声信号提取梅尔频率倒谱系数、翻转梅尔频率倒谱系数、短时能量和短时过零率组成特征参数,通过线性判别算法对特征参数进行特征融合。利用黑寡妇算法通过测试集对支持向量机模型的核参数和损失值进行优化得到B-SVM模型。利用Xeno-canto鸟鸣声数据集对本文算法进行了测试,结果表明该方法的识别准确率为93.23%。算法维度参数的大小和融合特征维度的高低是影响算法识别效果的重要因素。在相同条件下,文中所提的基于特征融合和B-SVM模型的鸟鸣声识别算法相较于其他特征参数和模型,识别的准确率更高,为野外鸟类识别提供了参考。

基于高频激光除漆的LIBS监测平台设计与应用研究

基于激光诱导击穿光谱(LIBS)技术的飞机漆层清洗监测,需要对峰值功率密度范围进行限定,以确保等离子体激发和漆层清洗的稳定性。然而,对于广泛使用的高频(kHz级)脉冲激光除漆技术,其峰值功率密度相对偏低,除漆过程中等离子体激发受到限制;且高频激光烧蚀材料产生的强连续背景光谱干扰了等离子体光谱采集。论文依据蒙皮功能漆层可控清洗需求,基于LabVIEW嵌入式开发系统的控制软件编写及激光清洗、光谱采集、控制与显示模块的集成,设计了一款适用于高频激光除漆的LIBS监测平台。选取2024-T3铝合金双漆层试样作为研究对象,采集波长介于360~700nm范围内的漆层/基体体系光谱(面漆层:Tc;底漆层:Pr;基体:As)。采用平滑滤波,基线校正和归一化对原始光谱进行预处理,并选取12条特征谱线进行主成分分析(PCA),其降维数据作为线性判别分析(LDA)的输入变量,以此建立PCA-LDA判别模型。最后将所建模型导入LIBS监测平台,通过试验验证了高频激光除漆LIBS监测平台的分类准确性。结果表明:仅以累积方差解释率大于85%作为主成分选取原则,不能满足除漆过程LDA的分类需要;通过优化LDA的主成分个数,最终选取前9个主成分作为LDA的输入,显著提升了LIBS平台的检测准确率,此时基于LIBS光谱的PCA-LDA模型分类准确率达92.5%。由此可见,设计的高频激光除漆LIBS监测平台能够完成漆层/基体体系不同结构层的材料识别,从而实现了高频脉冲激光可控除漆的有效监测。

基于FastICA-LDA的光伏并网逆变器故障诊断

为了实现逆变器开路故障诊断,提出了一种新的诊断方法。该方法采用快速独立成分分析算法判定逆变器是否发生单管开路故障,如果发生单管开路故障,计算旋转电流Id频域下的特征值,将这些特征值作为线性判别分析模型的输入值,最后由LDA模型输出逆变器工作状态编号,从而实现单管开路定位。经过MATLAB仿真验证表明,所提方法对光伏并网逆变器故障的诊断效果较好。

调制转移光谱对激光频率起伏分辨率的影响因素分析及优化方法

采用电光位相调制器对泵浦光进行位相调制,得到射频调制转移光谱(MTS),并研究MTS光谱的类色散信号中心过零点斜率优化问题。通过改变泵浦光的调制频率,泵浦光与探测光的光斑大小,研究MTS光谱信号过零点斜率与二者之间的参数依赖关系,在泵浦光调制频率为~3.6 MHz(大约是自然线宽的0.69倍)时,得到最佳的MTS光谱信号。最后利用最优的MTS光谱将DL Pro@852 nm激光频率锁定到铯原子D2线(F=4)-(F=5’)循环跃迁,在60 min采样时间内激光频率起伏约为170 kHz,与自由运转时激光器~11 MHz的频率起伏相比,频率起伏得到了显著改善。

Discriminant Classification Model of DNA Sequence

[Objective] The research aimed to construct the discriminant classification model of DNA sequence by combining with the biology knowledge and the mathematical method.[Method] According to the polarity nature of side chain radical in the amino acid,the classification information of amino acid which represented the sequence characteristic from the content and array situation of base was extracted from the different sequences that the amino acid content was different.The four-dimension vector was used to represent.Mahalanobis distance and Fisher discriminant methods were used to classify the given sequence.[Result] In the model,the back substitution rates of sample obtained by two kinds of classification methods were both 100%,and the consistent rate of classification was 90%.[Conclusion] In the model,the calculation method was simple,and the accuracy of classification result was higher.It was superior to the discriminant classification model which was only based on the base content.

基于时频感知双路径Conformer的语音增强

近年来,Conformer在语音领域的应用表现较为突出。该模块通过结合多头自注意力机制和卷积神经网络,能够同时关注短时和长时序列信息,从而在语音处理任务中表现出卓越的性能。在此基础上提出了一种基于时频感知双路径Conformer的语音增强网络(TFDPCNet)。首先,该网络将改进的Conformer结构作为核心,采用双路径结构,构成时频感知的双路径Conformer模块(TFDP-Conformer),增强了整体网络的时频提取能力;同时,为了减小时频特征融合的难度,提出了注意力门控交叉融合模块(AGCF),通过额外的注意力门进一步增强了网络训练过程中时频特征的交互,提高了时频特征的利用率;最后,引用度量鉴别器,并对其进行适当剪枝,使得增强后的音频和原始音频在量化评价指标上保持更高的一致性。实验结果表明,相比于TSTNN算法,TFDPCNet在主观和客观指标上都有明显提高。

Corticostriatal Neurons in the Anterior Auditory Field Regulate Frequency Discrimination Behavior

The anterior auditory field(AAF)is a core region of the auditory cortex and plays a vital role in discrimination tasks.However,the role of the AAF corticostriatal neurons in frequency discrimination remains unclear.Here,we used c-Fos staining,fiber photometry recording,and pharmacogenetic manipulation to investigate the function of the AAF corticostriatal neurons in a frequency discrimination task.c-Fos staining and fiber photometry recording revealed that the activity of AAF pyramidal neurons was significantly elevated during the frequency discrimination task.Pharmacogenetic inhibition of AAF pyramidal neurons significantly impaired frequency discrimination.In addition,histological results revealed that AAF pyramidal neurons send strong projections to the striatum.Moreover,pharmacogenetic suppression of the striatal projections from pyramidal neurons in the AAF significantly disrupted the frequency discrimination.Collectively,our findings show that AAF pyramidal neurons,particularly the AAF–striatum projections,play a crucial role in frequency discrimination behavior.

基于MIMO-FMCW雷达的多人生命体征检测

针对多输入多输出(MIMO)体制调频连续波(FMCW)雷达难于对室内环境多人生命体征进行准确检测的问题,本文提出一种基于MIMO-FMCW雷达的多人生命体征检测方法。首先对中频信号做距离维快速傅里叶变换(FFT)和Capon角度估计得到对应的距离角度图,利用二维恒虚警检测技术(2D-CFAR)和基于密度的聚类(DBSCAN)算法确定每个目标的距离角度信息,通过线性约束最小方差(LCMV)准则进行数字波束形成得到目标对应的慢时间维信号,并使用反正切函数完成相位信号的提取,最后利用谐波判别准则实现对呼吸和心跳信号频率的估计继而完成对多目标生命体征检测。实验结果表明,谐波判别准则实现了平均相对误差小于10%的呼吸率和心率检测精度,证明了该方法的有效性。

基于自适应滤波的TIADC校准技术研究

针对失调失配、增益失配和采样时间失配这三种失配,对TIADC的校准方法进行探究.依据已有的两通道TIADC低通滤波校准方法,将其扩展到了4通道,依据提出的拓展思路,可以将此方法拓展到更高的通道.另外,为了实现对频率的判别,提出了一种新的频率判别方法,可有效实现频率范围的判别.校准方法经仿真证明,在采样率为2 GHz的4通道TIADC中,使用不同的输入频率进行验证,经校准后,无杂散动态范围提升均在40 dB以上,校准效果明显.相对于目前的校准算法,该算法复杂度低,结构简单.

Anti-noise performance of the pulse coupled neural network applied in discrimination of neutron and gamma-ray

In this study,the anti-noise performance of a pulse-coupled neural network(PCNN)was investigated in the neutron and gamma-ray(n-γ)discrimination field.The experiments were conducted in two groups.In the first group,radiation pulse signals were pre-processed using a Fourier filter to reduce the original noise in the signals,whereas in the second group,the original noise was left untouched to simulate an extremely high-noise scenario.For each part,artificial Gaussian noise with different intensity levels was added to the signals prior to the discrimination process.In the aforementioned conditions,the performance of the PCNN was evaluated and compared with five other commonly used methods of n-γdiscrimination:(1)zero crossing,(2)charge comparison,(3)vector projection,(4)falling edge percentage slope,and(5)frequency gradient analysis.The experimental results showed that the PCNN method significantly outperforms other methods with outstanding FoM-value at all noise levels.Furthermore,the fluctuations in FoM-value of PCNN were significantly better than those obtained via other methods at most noise levels and only slightly worse than those obtained via the charge comparison and zerocrossing methods under extreme noise conditions.Additionally,the changing patterns and fluctuations of the FoMvalue were evaluated under different noise conditions.Hence,based on the results,the parameter selection strategy of the PCNN was presented.In conclusion,the PCNN method is suitable for use in high-noise application scenarios for n-γdiscrimination because of its stability and remarkable discrimination performance.It does not rely on strict parameter settings and can realize satisfactory performance over a wide parameter range.

Comparison of ISFs and LSFs in Speech/Music Discrimination System

The immittance spectral frequencies （ISFs） is proposed as a new set of classification features and compared with the linear spectral frequencies （LSFs） applied in a frame-level wideband speech/music discrimination system. These two sets of features can be shared by the classifier and coding module to reduce the total computational complexity, making our classification system suitable for multi-mode audio coding applications. A performance assessment and comparison of the features are made. The experiment results show that the ISFs and LSFs have similar good performance when using full covariance matrices in classification models and the ISFs perform slightly better when using diagonal matrices. Their statistical differences for speech and music signals are also revealed.

基于FDR和时频脉冲转换的长电缆缺陷极性识别研究

为解决采用频域反射技术进行长电缆缺陷检测时,其结果易受低频段数据缺失占比的影响,而难以判断电缆缺陷极性的问题,该文提出一种基于频域反射技术的电缆阻抗失配点时频脉冲转换算法以实现缺陷的定位和极性判别。首先,采用2阶Nuttall自卷积窗的快速傅里叶计算方法对不同类型的电缆阻抗失配点进行定位。其次,提出电缆阻抗失配点时频脉冲转换算法,利用高斯窄带包络信号良好的频段调节能力和时频特性,详细阐述了时频脉冲的参数设计和极性判断方法。之后,运用仿真,对不同类型的阻抗失配点进行时频脉冲转换,验证了该算法的有效性。最后,采用该算法对实验室含接头长1500m的10k V XLPE电缆进行实验验证。仿真和实验结果表明:时频脉冲转换算法可以有效地定位长电缆阻抗失配点并且实现不同类型阻抗失配点的极性识别;同时,不同长度电缆阻抗失配点的时频脉冲转换结果不受低频段数据缺失占比的影响,有效提高了长电缆阻抗失配点的极性识别率。

Discrimination Between Nuclear Explosions and Earthquakes: An Application of Wigner Distribution

In this paper,the nonstationary theory of Wigner Distribution is used to discriminate between underground nuclear explosions and natural earthquakes.Five underground explosions in Kazakhstan region and seven regional earthquakes in its adjacent areas have been analyzed.The result shows that the transient spectra of underground nuclear explosions are concentrated in the frequency range of 5-10 Hz,while the transient spectra of natural earthquakes are distributed widely from lower frequency to higher frequency.The transient frequency of nuclear explosions shows linearity in the first stage(0【t【0.75 s)and its initial frequency is negative.The transient frequency of natural earthquakes rapidly changes in a jumping form and its initial frequency alternates between being positive and negative.The obtained results show that the method is more effective than previous ones in discriminating between underground nuclear explosions and earthquakes.This paper also gives a preliminary explanation of the discrepancy

电容耦合相位鉴频器性能仿真分析

针对电容耦合相位鉴频器节点电压波形转换抽象和传统实验调试难的问题,采用软件建立电路虚拟仿真模型,通过匹配输入信号和电路参数对应关系,获得了关键节点的节点波形和输出波形,通过测试不失真数据和失真数据获得了鉴频特性曲线,通过多个参数的步进扫描方式逐步获得了电路各个元件的最佳参数,实践证明,这种电路可视化的虚拟仿真调试方法能形象直观地展示节点波形,能有效验证抽象理论知识,提升学习质量。

基于带宽调整的两种混合载波跟踪环路研究

针对高动态导致载波复现频率与实际载波频率相差较大的问题,锁频环和锁相环已无法满足环路的跟踪需求,依据频率判决因子实现三阶锁频环辅助四阶锁相环和四相鉴频器之间相互切换的2种混合载波跟踪环路算法;在三阶锁频环辅助四阶锁相环的基础上,通过相位判决因子完成对载波环带宽的动态调整。结果表明,在动态为5000/150 g/120 g、载噪比为42 dB/Hz、跟踪初始多普勒为300 Hz时,基于带宽调整的2种混合载波跟踪环路能准确地剥离出电文信息,而单一的三阶锁频环辅助四阶锁相环载波跟踪环路不能实现;当跟踪初始多普勒为0时,环路稳定跟踪后加入25/20 g/20 g的动态,基于带宽调整的2种混合载波跟踪环路可以重新完成稳定跟踪并剥离出电文信息,而三阶锁频环辅助四阶锁相环载波跟踪环路直接失锁;低载噪比下的基于带宽调整的2种混合载波跟踪环路的跟踪相位误差方差相对较小、跟踪精度较高。

相位/比例鉴频综合实验电路的设计与实现

为帮助学生更好地理解频率解调的知识点,掌握不同的频率解调方案,设计了一套相位/比例鉴频综合实验电路。利用信号源产生调频波作为电路输入,通过选择开关实现比例鉴频器和叠加型相位鉴频器的灵活切换,达到两种电路形式有机结合的目的。通过鉴频功能、鉴频灵敏度以及限幅作用的测试与分析,深入探讨两种鉴频器的异同,实现理论和实践的融会贯通。教学实践表明,该实验效果良好,适用于本科实验教学、大学生科研和电子设计竞赛等多种场合。

微型离子漏斗减少低质量歧视效应的理论模拟研究

为减少微型离子漏斗的低质量歧视问题,本文提出了一种梯度下降射频(radio frequency,RF)信号施加方法,通过在漏斗出口端的多片电极上施加幅值递减的RF信号,提高低质荷比离子的传输效率。采用电场模拟软件SIMION和离子运动轨迹仿真软件AXSIM模拟分析微型离子漏斗在施加梯度下降RF信号时的离子传输性能。结果表明:相较于传统的RF施加方式,梯度下降RF施加方法能有效减少低质量歧视问题,且不影响高质量段的离子传输效率。另外,详细研究了在梯度下降RF施加方式下,RF的频率和直流场梯度等参数对离子传输效率的影响。进一步对梯度下降RF施加方法简化后,离子传输效率略有下降,但仍优于传统的RF施加方式,且降低了操作难度,提升了方案实施的可行性。