推导法评估编码器细分误差

为实现高精度编码器细分误差的快速评估,提出了一种Lissajou图形推导法.通过理论分析和计算机仿真,得出:在一定条件下,lissajou图形的向径偏差与细分误差之间存在确定关系,可以由向径偏差各次谐波直接推导出细分误差的各次谐波,绘出细分误差曲线.与传统方法测量得到的静态细分误差曲线进行对比,实验结果表明,运用该方法,数据分析处理时间短,可以用于编码器工作现场的快速检测.     

幅频特性的数学分析

根据数控装置检测系统中传感器信号电路工作要求,以共射电压放大电路为例,分别考虑耦合电容、旁路电容、结间电容和分布电容对不同信号频率的作用,分析了电路的低频特性和高频特性,给出了上下限截止频率的解析式.由此得出,电路其他参数一定时,在低频段,下限截止频率与耦合电容、旁路电容成反比,在高频段,上限截止频率与等效输入输出电容成反比,从而为传感器系统设计提供理论依据.     

OFDMA系统上行链路频偏的盲估计

本文介绍了直接数字频率合成技术DDS(Direct Digital Frequency Synthesizers)工作原理,分析了其理想频谱;采用信号分析的方法深入研究了DDS存在相位截断和幅度量化时引入的杂散信号频谱分布的规律和性能;定性讨论了DAC非理想性对DDS输出杂散谱的影响.最后进行计算机仿真分析并验证了结论.所得规律性结论为DDS设计和工程应用开发中的参数选取、杂散评估和杂散抑制提供重要的理论依据和经验参考.     

地图制图在广播覆盖测试分析中的应用

将广播信号场强覆盖测试数据用图形化的方式表现出来,使枯燥的数据看起来更加方便、直观,为分析地理、地貌对广播信号场强覆盖的影响提供了理论依据,为发射机各项参数的分析、调整提供了详细的参考数据,为改善广播信号的覆盖奠定了良好的基础.     

基于到达时间差直方图的信号分选算法研究

到达时间差(TDOA)直方图分析是电子支援侦察雷达信号主分选的基础;相关信号分选算法的性能与TDOA直方图脉冲重复间隔(PRI)检测门限的设定密切相关。为揭示PRI检测门限与TDOA直方图参数之间的关系,解决传统PRI检测门限依靠经验设定、无法灵活调整的问题,该文从分析TDOA直方图与脉冲序列的统计性质入手,推导了直方图稳定PRI、抖动PRI和参差PRI检测门限的解析表达式,提出了基于TDOA直方图PRI检测的信号分选算法,并通过仿真验证了算法的有效性。     

基于小信号等效电路模型的SiGe HBT 高频特性模拟分析

给出了fr为15 GHz的SiGe HBT器件的高频小信号等效电路模型;运用微波网络理论,在Matlab软件平台上模拟出器件的S参数和H21参数曲线,模拟结果与实测结果相吻合;根据电路的拓扑结构,分析了管壳封装带来的寄生参数对器件高频性能的影响;根据稳定性判据,计算了器件的稳定性与工作频率之间的关系.为器件的设计和应用提供了理论依据.     

一种优化的微弱信号检测方法

针对混沌海杂波背景下的微弱信号检测问题,结合互补集成经验模态分解理论,提出了一种优化的核极限学习机微弱信号检测方法。采用互补集成经验模态分解法将混沌信号分解为一系列固有模态函数,通过核极限学习机对经相空间重构后的各模态函数分别建立预测模型,利用人工蜂群算法对核极限学习机的正则化系数和核参数进行优化,重构预测信号,从预测误差中检测出混沌海杂波背景中的微弱信号(瞬态信号与周期信号)。分别以Lorenz 系统和IPIX 雷达海杂波数据为例进行了仿真,并研究了不同强度的噪声对微弱信号检测的影响。结果表明:该方法可以有效地从混沌背景中检测出微弱目标信号,当系统不存在噪声时,Lorenz 系统得到的均方根误差0. 000 000 12 (-118. 959 1 dB)比传统极限学习机方法的均方根误差0. 001 345 08(-80. 154 7 dB)降低了4 个数量级;若SNR逸0 dB,噪声对微弱目标信号检测的影响可以忽略;但当SNR<-7 dB,则无法检测出微弱信号。     

一种减小Duffing系统可检测断续正弦信号频率范围的方法

本文针对Duffing混沌系统利用状态变化检测已知断续正弦信号时,正弦信号频率范围较宽的问题,根据Mélnikov方法中的系统参数与待测信号幅度、频率之间的关系,分析证明了增加Duffing系统的阻尼参数提高系统正弦信号检测能力的方法,最后给出了在有、无噪声情况下,调整阻尼参数后Duffing系统对断续正弦信号的检测仿真结果.结果表明本文所提出的方法是有效的.     

采用相位推算法检测FSK信号

随着铁路的迅速发展,需要更多的信息量和更加有效的铁路信号检测方法,为保证列车的安全正点运行,对铁路移频轨道电路进行实时检测.利用频谱分析法能求出移频信号的中心频率和低频参数,但不能得出移频信号的上边频和下边频.而相位推算法正好弥补了这一缺点.文中介绍了一种相位推算法检测FSK信号方法,从而得出移频信号的中心频率、低频参数、上边频和下边频这些参数.     

电磁波在海水中的传播特性研究

利用电磁场传播所满足的MaxWell方程组,计算和分析了电磁波在海水中传播时的参数及特征,并分析了海水中电磁波的能量特征,为海水中通信、信号探测、导航等方面工作提供了理论依据.     

100Gbit/s DP-QPSK调制光星座图测试及分析

由于调制光信号质量的好坏影响到传输和接收信号质量的好坏,因此对100Gbit/s系统中的数字光信号的测量与分析十分重要。文章对100Gbit/s transponder中调制光信号的生成原理进行了分析,对数字光信号测试中的OSNR(光信噪比)、EVM(误差矢量幅值)和星座图等几个参数进行了必要的理论探讨。同时也分析了各种QPSK(四相相移键控)信号星座图的图形,为使用调制器分析问题提供了有效参考。     

基于FPGA的LCD测试用信号发生器设计

在检测液晶屏特性和质量时,需要控制液晶屏显示一些标准信号。已有的一些信号产生设备产生的是AV信号、VGA信号或YPbPr信号等模拟制式的信号。模拟制式的信号需要经过图形处理器（GPU）转换成数字LVDS信号,然后输入到液晶屏的扫描控制电路产生相应图像。这个过程不可避免的会使图像信号产生一定程度的失真与损耗,影响图像质量。旨在设计一种新型信号发生器,该发生器产生的数字图像信号转换成数字LVDS信号后,直接输入液晶屏,以避免信号传输过程产生的失真与损耗。     

Evaluation of Autocorrelation Techniques for Detection of the Fetal Electrocardiogram

This paper presents an evaluation of autocorrelation techniques for the detection of fetal electrocardiogram signals from abdominal recordings. Raw signals are digitized, then processed and analyzed by a digital computer. The effect of elimination of the maternal signal and of fluctuations in the fetal period is demonstrated. Correlation parameters such as length of signal and sampling rate are investigated.     

基于联合检测方法的雷达信号分选跟踪机设计

雷达信号分选是雷达对抗中一个重要的组成部分,只有从随即交迭的信号流中分选出各个雷达脉冲序列之后才能进行信号参数的测量、分析、识别。目前基于PRI参数提出很多分选方法,针对各种方法的优缺点,研究了一种基于SDIF算法和序列相关法联合检测的被动雷达信息处理系统信号分选跟踪机,经仿真证明,基于SDIF与序列相关法的联合检测增加了检测概率,具有较好的鲁棒性,可以较好地对空间多部不同雷达信号进行准确分选,正确给出跟踪波门。该信号分选跟踪机已在工程中应用。     

Maximum likelihood estimation of signals in autoregressive noise

Time series modeling as the sum of a deterministic signal and an autoregressive (AR) process is studied. Maximum likelihood estimation of the signal amplitudes and AR parameters is seen to result in a nonlinear estimation problem. However, it is shown that for a given class of signals, the use of a parameter transformation can reduce the problem to a linear least squares one. For unknown signal parameters, in addition to the signal amplitudes, the maximization can be reduced to one over the additional signal parameters. The general class of signals for which such parameter transformations are applicable, thereby reducing estimator complexity drastically, is derived. This class includes sinusoids as well as polynomials and polynomial-times-exponential signals. The ideas are based on the theory of invariant subspaces for linear operators. The results form a powerful modeling tool in signal plus noise problems and therefore find application in a large variety of statistical signal processing problems. The authors briefly discuss some applications such as spectral analysis, broadband/transient detection using line array data, and fundamental frequency estimation for periodic signals     

Symbol error probability analysis of a multiuser detector for M-PSKsignals based on successive cancellation

A narrow-band multiuser receiver based on successive signal detection and subtraction, is considered. The symbol error probability (SEP) for M-PSK modulated signals is evaluated and analytical approximations for the SEP of the individual signals are presented and compared with results obtained from simulations. For geometrically related signal amplitudes, a constant minimum distance can be guaranteed independent of the number of signals. The required amplitude ratio is shown to be related to M and the number of co-channel signals. Optimizing the transmitted power for the different signals while ensuring the same SEP is then addressed and closed-form expressions of the signal amplitude ratios are derived. The effect of inaccurately estimated signal parameters due to noise is also analyzed. SEP results are presented for synchronous signals in an additive white Gaussian noise environment     

分数阶Fourier变换对LFM信号的特征参数估计能力仿真评估

将分数阶傅里叶变换（FrFT）对线性调频（LFM）信号处理方法应用到雷达侦察信号分选与参数估计中,研究FrFT对LFM信号在低信噪比下的检测与参数估计能力。设定了雷达侦察信号背景,制定了仿真验证流程,考察了FrFT对LFM信号的调频率和中心频率的估计能力,对比了不同信噪比下的参数估计运算时间。仿真结果验证了该算法可以完成低信噪比条件下雷达侦察LFM信号特征参数的估计。     

Adaptive Threshold Detection and Estimation of Linear Frequency-Modulated Continuous-Wave Signals Based on Periodic Fractional Fourier Transform

The fractional Fourier transform (FRFT) has been used to detect and estimate the parameters of linear frequency-modulated continuous-wave (LFMCW) in low probability of intercept radar waveforms. The FRFT, which is optimal for single linear frequency-modulated (LFM) signals, becomes sub-optimal when applied to LFMCW signals because the observed waveform of this type of signal is composed of concatenated LFM pulses. A new signal processing method, called the periodic FRFT (PFRFT), is proposed for the detection of LFMCW signals. First, the discrete PFRFT is studied and the signal processing gain of this transform for LFMCW signals is analyzed. Second, an adaptive threshold detection and estimation algorithm for LFMCW signals is formulated after analysis of the test statistics of the squared modulus of LFMCW signals when using the probability density function in the presence of Gaussian white noise. It is then proved that PFRFT-based estimation is equivalent to maximum likelihood estimation in the detection and estimation of LFMCW signals. Finally, the results of both the theoretical analysis and verification simulations show that the PFRFT significantly outperforms the FRFT for LFMCW signals.     

一种新的卫星通信信号快速盲检测方法

提出了一种卫星通信信号快速盲检测算法,该算法能够适应频谱不重叠的多信号环境,并能准确估计信号的数量、中心频率及带宽等参数.算法既高效又简单,所需数据量少且适应低信噪比条件,适于在星载设备上实现.理论分析和仿真及测试结果证明了算法的有效性.     

基于模糊聚类的常规通信信号自动分选方法

为解决从干扰环境中自动分选出常规通信信号的问题,提出了一种基于模糊聚类的常规通信信号分选方法.该方法首先利用区分度函数确定最优的相关度阈值参数,然后利用模糊聚类算法对利用频域检测和测向得到的测量集进行信号分选,并对分选后的通信信号进行特征参数估计.实验结果表明,该算法能够在不做任何假定的条件下对常规通信信号进行正确分选,并对窄带信号的特征参数进行准确估计.