脑电波分析及处理综述

大脑由数以亿计的神经元细胞组成,当大脑活动时,神经元之间的联系是依靠着同步发生的突触后产生的电位,这些电位经综合后形成的宏观现象就是脑电波.脑电波是自发的有节律的神经元活动且能够反映人体大脑状态如清醒和睡眠等等.现代研究已证实脑波可划分为4个波段:δ波(0.5～4 Hz)、θ波(4～8 Hz)、α波(8～13 Hz)、...     

基于AR模型的小波变换在脑电信号消噪中的应用

提出了基于自回归模型(ARM)与小波变换的脑电信号分析方法,并利用他来消除脑电信号中的噪声干扰。小波变换是一种多分辨率的时间尺度分析方法,他能够将信号划分为不同频段的子带信号。根据小波变换的这一特性,对采样获得的脑电信号进行各尺度分解及消噪分析,并给出了各尺度分解结果及消噪结果。利用小波变换能有效去除脑电信号中的噪声干扰。     

A CMOS frequency synthesizer with an injection-locked frequencydivider for a 5-GHz wireless LAN receiver

A fully integrated 5-GHz phase-locked loop (PLL) based frequency synthesizer is designed in a 0.24 μm CMOS technology. The power consumption of the synthesizer is significantly reduced by using a tracking injection-locked frequency divider (ILFD) as the first frequency divider in the PLL feedback loop. On-chip spiral inductors with patterned ground shields are also optimized to reduce the VCO and ILFD power consumption and to maximize the locking range of the ILFD. The synthesizer consumes 25 mW of power of which only 3.8 mW is consumed by the VCO and the ILFD combined. The PLL has a bandwidth of 280 kHz and a phase noise of -101 dBc/Hz at 1 MHz offset frequency. The spurious sidebands at the center of adjacent channels are less than -54 dBc     

A 0.25-/spl mu/m CMOS quad-band GSM RF transceiver using an efficient LO frequency plan

This paper describes a single-chip CMOS quad-band (850/900/1800/1900 MHz) RF transceiver for GSM/GPRS applications. It is the most important design issue to maximize resource sharing and reuse in designing the multiband transceivers. In particular, reducing the number of voltage-controlled oscillators (VCOs) required for local oscillator (LO) frequency generation is very important because the VCO and phase-locked loop (PLL) circuits occupy a relatively large area. We propose a quad-band GSM transceiver architecture that employs a direct conversion receiver and an offset PLL transmitter, which requires only one VCO/PLL to generate LO signals by using an efficient LO frequency plan. In the receive path, four separate LNAs are used for each band, and two down-conversion mixers are used, one for the low bands (850/900 MHz) and the other for the high bands (1800/1900 MHz). A receiver baseband circuit is shared for all four bands because all of their channel spaces are the same. In the transmit path, most of the building blocks of the offset PLL, including a TX VCO and IF filters, are integrated. The quad-band GSM transceiver that was implemented in 0.25-/spl mu/m CMOS technology has a size of 3.3/spl times/3.2 mm/sup 2/, including its pad area. From the experimental results, we found that the receiver provides a maximum noise figure of 2.9 dB and a minimum IIP3 of -13.2dBm for the EGSM 900 band. The transmitter shows an rms phase error of 1.4/spl deg/ and meets the GSM spectral mask specification. The prototype chip consumes 56 and 58 mA at 2.8 V in the RX and TX modes, respectively.     

A neurosynaptic model of state-dependent EEG wave generation in thesubcortico-cortical system

A neurosynaptic model of the subcortico-cortical system is presented in order to analyze the mechanism for the generation of EEG rhythms with specific state-dependent spectral patterns. The model is based on the interaction among the infraslow, as well as basic, rhythms of the PSP's (postsynaptic potentials) trains from which CSD's (current source densities) or cortical surface potentials emerge. The model system was simulated by two trains of positive and negative cortical surface potentials within the same period, according to the thalamic clock as modulated by the infraslow rhythms of the midbrain reticular system. The simulated EEG's showed rhythmic waxing and waning sawtooth-like waves with no frequency fluctuation, but with some spectral broadband peaks at the basic repetitive frequency, as well as its harmonics     

An experimental study to investigate the effects of a motion tracking electromagnetic sensor during EEG data acquisition

A power spectral analysis study was conducted to investigate the effects of using an electromagnetic motion tracking sensor on an electroencephalogram (EEG) recording system. The results showed that the sensors do not generate any consistent frequency component(s) in the power spectrum of the EEG in the frequencies of interest (0.1-55 Hz).     

自偏置锁相环结构及其稳定性条件分析

给出了基于自偏置技术的电荷泵锁相环电路,压控振荡器的工作频率动态地建立了电路内部所有的偏置电压和电流,从而实现了固定衰减因子,固定环路带宽与工作频率之比,这二者由电容的比率决定,极大地实现了电路设计的工艺无关性,同时也得到了小的相位抖动,最后,对这种锁相环的稳定性进行了一定的分析。     

一种锁相频率合成系统的设计

描述了以MC145152和MC1648芯片为核心,采用锁相频率合成技术来实现电压控制LC振荡器的设计思路、方法及指标测试。本系统可以产生高稳定度的正弦信号,输出频带在5~25 MHz范围内,并实时显示;输出频率的稳定度达到10-3以上。该系统在通信领域有广泛的应用前景。     

Low-jitter process-independent DLL and PLL based on self-biasedtechniques

Delay-locked loop (DLL) and phase-locked loop (PLL) designs based upon self-biased techniques are presented. The DLL and PLL designs achieve process technology independence, fixed damping factor, fixed bandwidth to operating frequency ratio, broad frequency range, input phase offset cancellation, and, most importantly, low input tracking jitter. Both the damping factor and the bandwidth to operating frequency ratio are determined completely by a ratio of capacitances. Self-biasing avoids the necessity for external biasing, which can require special bandgap bias circuits, by generating all of the internal bias voltages and currents from each other so that the bias levels are completely determined by the operating conditions. Fabricated in a 0.5-μm N-well CMOS gate array process, the PLL achieves an operating frequency range of 0.0025 MHz to 550 MHz and input tracking jitter of 384 ps at 250 MHz with 500 mV of low frequency square wave supply noise     

Detection of seizure precursors from depth-EEG using a sign periodogram transform

Brief bursts of focal, low amplitude rhythmic activity have been observed on depth electroencephalogram (EEG) in the minutes before electrographic onset of seizures in human mesial temporal lobe epilepsy. We have found these periods to contain discrete, individualized synchronized activity in patient-specific frequency bands ranging from 20 to 40 Hz. We present a method for detecting and displaying these events using a periodogram of the sign-limited temporal derivative of the EEG signal, denoted joint sign periodogram event characterization transform (JSPECT). When applied to continuous 2-6 day depth-EEG recordings from ten patients with temporal lobe epilepsy, JSPECT demonstrated that these patient-specific EEG events reliably occurred 5-80 s prior to electrical onset of seizures in five patients with focal, unilateral seizure onsets. JSPECT did not reveal this type of activity prior to seizures in five other patients with bilateral, extratemporal or more diffuse seizure onsets on EEG. Patient-specific, localized rhythmic events may play an important role in seizure generation in temporal lobe epilepsy. The JSPECT method efficiently detects these events, and may be useful as part of an automated system for predicting electrical seizure onset in appropriate patients.     

四相鉴频器辅助的高动态BOC信号载波跟踪

叉积鉴频器的输出频率范围比较窄,捕获信号以后的多普勒频偏可能不在其跟踪范围内。针对此问题,提出了使用四相鉴频器( FQFD )算法辅助已经成型的二阶锁频环加三阶锁相环模型。首先,利用四相鉴频器的非线性特性将接收信号频偏大步长牵引到较低范围,然后使用锁频环消除其大部分动态性,最后利用锁相环跟踪精度高的特点实现高动态二进制偏移载波( Binary Offset Car-rier,BOC)信号载波的快速准确跟踪。在分析各跟踪模块算法的基础上,讨论了其本身的热噪声误差、动态适应力以及最优带宽等相关问题,理论分析和仿真结果验证了该方法比原有跟踪算法提高了300 Hz左右的鉴频范围,并且跟踪效果良好。     

基于有记忆递归神经网络的脑电特征情感识别研究

为了提高脑电信号多分类的情感识别率,文中选用上海交通大学提供的SEED脑电信号数据集,对其进行分频带特征提取。将脑电数据的微分熵特征、微分不对称性特征和有理不对称性特征通过线性动力系统平滑特征后,与功率谱密度特征进行分类效果比较,再利用有记忆递归神经网络的方法进行分类,发现提取的微分熵特征经过分类的效果好。在对3种情感进行分类的过程中,采用长短时记忆神经网络分类相比于其他机器学习方法识别率有所提高,情感识别的平均准确率可达到95.045 9%。     

Dominant frequency analysis of EEG reveals brain's response duringinjury and recovery

A new method of monitoring and analyzing electroencephalogram (EEG) signals during brain injury is presented, EEG signals are modeled using the autoregressive (AR) technique to obtain the frequencies where there are peaks in the spectrum. The powers at these dominant frequencies are analyzed to reveal the state of brain injury during an experimental study involving progressive hypoxia, asphyxia, and recovery. Neonatal piglets (n=8) were exposed to a sequence of 30 min of hypoxia (10% oxygen), 5 min of room air, and 7 min of asphyxia. They then received cardiopulmonary resuscitation and were subsequently monitored for 4 h. An optimal AR model order of 6 was obtained for these data, resulting in 3 dominant frequencies. These dominant frequencies, referred to as the low, medium, and high frequency components, fell in the bands 1.0-5.5 Hz, 9.0-14.0 Hz, and 18.0-21.0 Hz, respectively. A remarkable feature of the authors' data is the spectral dispersion, or diverging trends in the 3 frequency bands. During hypoxia, the relative powers of the medium and high-frequency components of EEG increased up to 160% and 176%, from their respective baseline values. During the first minute of asphyxia the medium- and high-frequency powers (relative to baseline) increased by 280-400%. The power in all 3 frequency components went down to nearly zero within 40-80 s of asphyxia. During recovery, the phenomenon of burst-suppression was clearly exhibited in the low-frequency component. A new index, called mean normalized separation, representing the degree of disproportionality in the recovery of powers of the 3 dominant components relative to their mean recovered power, is presented as a possible single indicator of electrical function recovery. In conclusion, dominant frequency analysis helps reveal the brain's graded electrical response to injury and recovery     

Quantitative analysis of the EEG--general concepts and animal studies

Quantification of the EEG using digital computers is based on complex subjective processes of data reduction and feature extraction. In this paper, the signal characteristics of the EEG are identifred and major developments in the field of computerized electroencephalography (such as spectral analysis, compressed spectral arrays, etc.) are surveyed. Particular attention is given to signal analysis techniques used to characterize 1) background (stationary) EEG activity, and 2) interrelated multichannel EEG activity. The fast Fourier transform (FFT) has dominated approaches used to study background activity while cross-spectrum and coherence analysis have extended frequency or spectrum analysis into frequency-limited relationships between channels. In the realm of applications, the use of the digital computer-analyzed EEG to quantify 1) vigilance state dependent EEG changes, 2) the central effect of pharmacological agents, and 3) the normal ontogeny of the cortical and hippocampal EEG is described.     

Analysis and Software Implementation of a Robust Synchronizing PLL Circuit Based on the pq Theory

This paper presents the analysis and software implementation of a robust synchronizing circuit, i.e., phase-locked loop (PLL) circuit, designed for use in the controller of active power line conditioners. The basic problem consists of designing a PLL circuit that can track accurately and continuously the positive-sequence component at the fundamental frequency and its phase angle even when the system voltage of the bus, to which the active power line conditioner is connected, is distorted and/or unbalanced. The fundamentals of the PLL circuit are discussed. It is shown that the PLL can fail in tracking the system voltage during startup under some adverse conditions. Moreover, it is shown that oscillations caused by the presence of subharmonics can be very critical and can pull the stable point of operation synchronized to that subharmonic frequency. Oscillations at the reference input are also discussed, and the solution of this problem is presented. Finally, experimental and simulation results are shown and compared     

A 50-GHz Phase-Locked Loop in 0.13-μ m CMOS

A 50-GHz charge pump phase-locked loop (PLL) utilizing an LC-oscillator-based injection-locked frequency divider (ILFD) was fabricated in 0.13-mum logic CMOS process. The PLL can be locked from 45.9 to 50.5 GHz and output power level is around -10 dBm. The operating frequency range is increased by tracking the self-oscillation frequencies of the voltage-controlled oscillator (VCO) and the frequency divider. The PLL including buffers consumes 57 mW from 1.5/0.8-V supplies. The phase noise at 50 kHz, 1 MHz, and 10 MHz offset from the carrier is -63.5, -72, and -99 dBc/Hz, respectively. The PLL also outputs second-order harmonics at frequencies between 91.8 and 101 GHz. The output frequency of 101 GHz is the highest for signals locked by a PLL fabricated using the silicon integrated circuits technology.     

Motor Imagery EEG Fuzzy Fusion of Multiple Classification

Due to the volume conduction, electroencephalogram (EEG) gives a rather blurred image of brain activities. It is a challenge for generating satisfactory performance with EEG. This paper studies the multiple areas fusion of EEG classifiers to improve the motor imagery EEG classification performance. Two feature extraction methods are employed to extract the feature from three different areas of EEG. One is power spectral density (PSD), and the other is common spatial patterns (CSP). Classifiers are designed based on the well-known linear discrimination analysis (LDA). The fusion of the individual classifiers is realized by means of the Choquet fuzzy integral. It is demonstrated that the proposed method comes with better performance compared with the individual classifier.     

A low-jitter 125-1250-MHz process-independent and ripple-poleless0.18-μm CMOS PLL based on a sample-reset loop filter

This paper describes a low-jitter phase-locked loop (PLL) implemented in a 0.18-μm CMOS process. A sample-reset loop filter architecture is used that averages the oscillator proportional control current which provides the feedforward zero over an entire update period and hence leads to a ripple-free control signal. The ripple-free control current eliminates the need for an additional filtering pole, leading to a nearly 90° phase margin which minimizes input jitter peaking and transient locking overshoot. The PLL damping factor is made insensitive to process variations by making it dependent only upon a bandgap voltage and ratios of circuit elements. This ensures tracking between the natural frequency and the stabilizing zero. The PLL has a frequency range of 125-1250 MHz, frequency resolution better than 500 kHz, and rms jitter less than 0.9% of the oscillator period     

Differences of EEG between Eyes-Open and Eyes-Closed States Based on Autoregressive Method

Autoregressive （AR） power spectral density estimate method was used to analyze the electroencephalogram （EEG） signals in eyes-open and eyes-closed states. From the topographical distributions of delta, theta, alpha, and beta power spectrum, these two states can be clearly discriminated. In these two states, frontal areas were activated in delta power, both frontal and occipital areas were activated in theta band, and occipital areas were activated in alpha and beta bands. These four bands had significantly higher power in frontal, parietal, and occipital areas when eyes were close. The results also implied that the optimum order of AR model could be more suitable for estimating EEG power spectrum of different states.     

利用脑电空间高频分量分离深,浅层偶极子源

从头皮观测脑电中把由深层源产生的部分与浅层源产生的部分分开，据以观察大脑内的深层电活动细节是在理论和临床上有重要意义的课题，本文根据对深、浅层偶极子源在头皮上产生电位的空间频率分析，提出利用脑电的空间高频分量对浅层源定位，进而把浅层源产生的电位从脑电中分离出去的方法，并将Ｍａｒｑｕａｒｄｔ优化算法由空域推广到空频域，仿真实验表明，此法可以较准地定位浅层源，从而有效地把脑电中深，浅层源的贡献区分开来