基于复阻抗咽造影的吞咽事件检测与智能识别方法

吞咽障碍早期筛查是降低吞咽障碍发病率的重要手段,而对吞咽事件(SE)的准确识别是吞咽障碍筛查和治疗过程中的关键环节。阻抗咽造影(IPG)是一种新型非侵入式吞咽事件检测方法,但现有的IPG技术仅检测阻抗幅值而忽略了同样重要的相位信息。为了实现对吞咽事件的全面检测及智能识别,该文提出一种基于整周期数字锁相放大原理的复阻抗咽造影(CIPG)检测方法,设计了基于FPGA的CIPG检测系统以连续描记吞咽过程的复阻抗(阻抗幅值和相位)信息,并设计了基于连续小波变换(CWT)和GoogLeNet相结合的吞咽事件智能识别算法。设计了包含喝水、干咽、吃面包、吃酸奶、咳嗽等5种吞咽事件的识别实验,实验结果表明,仅利用阻抗幅值信息时的吞咽事件识别准确率为86.1%,而同时利用阻抗幅值和相位信息时的识别准确率为95.7%,后者的识别准确率高于其它算法。该研究证实了CIPG技术和吞咽事件智能识别算法的有效性与优越性,为下一步开发基于CIPG的吞咽障碍早期筛查方法奠定了理论和技术基础。     

Transmural versus nontransmural in situ electrical impedance spectrum for healthy, ischemic, and healed myocardium

Electrical properties of myocardial tissue are anisotropic due to the complex structure of the myocardial fiber orientation and the distribution of gap junctions. For this reason, measured myocardial impedance may differ depending on the current distribution and direction with respect to myocardial fiber orientation and, consequently, according to the measurement method. The objective of this study is to compare the specific impedance spectra of the myocardium measured using two different methods. One method consisted of transmural measurements using an intracavitary catheter and the other method consisted of nontransmural measurements using a four-needle probe inserted into the epicardium. Using both methods, we provide the in situ specific impedance spectrum (magnitude and phase angle) of normal, ischemic, and infarcted pig myocardium tissue from 1 kHz to 1 MHz. Magnitude spectra showed no significant differences between the measurement techniques. However, the phase angle spectra showed significant differences for normal and ischemic tissues according to the measurement technique. The main difference is encountered after 60 min of acute ischeimia in the phase angle spectrum. Healed myocardial tissue showed a small and flat phase angle spectrum in both methods due tothe low content of cells in the transmural infarct scar. In conclusion, both transmural and nontransmural measurements of phase angle spectrum allow the differentiation among normal, ischemic, and infarcted tissue.     

相位加权阵列天线的互耦分析及补偿

采用分段正弦基函数Galerk in法计算了阵列天线的阻抗矩阵,利用互耦阻抗方程分析了相位加权阵列的幅相恶化程度,且用矩量法分析了互耦对两种相对加权阵列天线性能的影响。提出了一种互耦补偿的方法即网络分析法,仿真结果表明了这种补偿方法的正确性和有效性。     

Phase regression approach for estimating the parameters of a noisy multifrequency signal

A novel approach for estimating the parameters of a multifrequency signal from discrete samples corrupted by additive noise is presented. An established mathematical model indicates that noise influence on the discrete phase and amplitude spectra is equivalent to additive phase and amplitude noise, respectively. On this basis, a simple algorithm is proposed to estimate the frequency and phase of each sinusoid component by linear regression on the phase spectra of segmented signal blocks, while an amplitude estimator is directly derived from the spectrum of the window function. The circular nature of the phase spectrum is thoroughly explored. Also, an algorithmic scheme is presented. The derived variances of the estimators show that for a noisy signal this approach provides superior accuracy over the traditional approaches. Simulations and engineering application confirm the validity of the presented method.     

Impedance Transformations For The Generalized Reflection Modulator

A procedure is given for obtaining the impedance transformer which will produce a prescribed pair of phasor reflection coefficients by transformation from a given pair of impedance states terminating the transformer. The transformer may be used in a general two-state reflection modulator: as a phase shifter with phase change at constant amplitude or as an amplitude modulator with level shift at constant or variable phase. The condition governing the reflection coefficients available from a given pair of impedance states is given. Examples and limitations are discussed.     

Design of broad-band lumped-element baluns with inherent impedance transformation

This paper reports on a novel lumped balun topology, the second-order lattice balun, with broad-band performance. The design is based on synthetic transmission lines operating as impedance transformers. The characteristic impedance of the synthetic transmission lines may be chosen to obtain inherent impedance transformation. An analytical investigation results in closed formulas for optimum performance over a given bandwidth. It is shown that it is possible to design for equal ripple in amplitude balance and input reflection coefficient. The phase balance is theoretically perfect over the entire bandwidth. The concept is experimentally validated by a 1-GHz prototype fabricated with surface mounted chip components. It exhibits an amplitude balance better than 0.5 dB and a phase balance better than /spl plusmn/8/spl deg/ over an octave bandwidth. The effective area of the prototype is 7 /spl times/ 9 mm/sup 2/.     

A variational method for designing adaptive bandlimited wavelets

This paper proposes a new method of estimating an orthogonal bounded spectrum wavelet from a given signal. The method is based on minimizing the distance of the wavelet and the given signal in the sense of the metric of the L ² space. In this method, the amplitude and phase of the mother wavelet are optimized simultaneously. The Lagrange multipliers technique is applied to consider the constraints due to the bounded spectrum wavelet and orthogonality conditions. The variational method reduced the optimal matching problem to the solution of a set of functional equations for the amplitude and phase of the optimal-matched bandlimited wavelet spectrum. Continuous functional equations are written with respect to Fourier coefficients of phase of transfer function of the quadrate low-pass filter at the sampled frequencies, and asset of discrete algebraic equations allows us to design the wavelet directly from the signal of interest. To demonstrate the performance of the presented method in this paper, it is employed to determine the matched wavelets of some specified signals.     

采用FPGA的动力锂电池内阻智能检测装置

为了实现对动力锂电池内阻的高精度检测,通过对锂电池内部结构和工作原理进行分析,建立了等效电路模型,并采用交流注入法设计了电池内阻在线智能检测装置。将微小的交变激励电流信号施加在电池两端,同时利用在FPGA平台上设计的正交锁相放大电路测量电池两端产生的响应电压信号,并通过引入圆周模式的CORDIC算法实现矢量运算,大幅提升了数据处理速度,最后根据欧姆定律计算出电池内阻的阻抗幅值和相位角。实验结果表明:设计的内阻智能检测装置能够方便测量出电池在各频段的阻抗谱,且具有较高的测量精度和稳定度,平均误差仅为0.231%,最大偏差也仅为0.452%,可为新能源汽车动力电池的健康诊断提供可靠的技术保障。     

相位量化DRFM性能分析

本文提出了一种数字射频存储器(DRFM)偏移相位量化方法,它是在传统相位量化方法的基础上通过增加一个相位偏移而得到.通过傅立叶分析,得到了其谐波寄生信号性能计算公式,结果表明,其性能与传统相位量化方法相同.其优点是,由于其良好的对称性,更适合于硬件电路实现.在此基础上,提出了一种用D/A变换器代替加权求和网络实现相位量化DRFM信号重构的新方法,解决了多位相位量化DRFM工程实现的困难.采用计算机仿真方法对由于D/A变换幅度量化引起的性能变化进行了分析,表明当D/A变换器位数接近于相位量化位数时就可以获得满意的效果.     

基于相移偏移和匹配追踪的探地雷达成像方法

把非均匀采样快速傅里叶变换(NUFFT)算法引入到探地雷达(GPR)成像的相移偏移算法中,避免了常规相移算法中的插值运算,实现了相移偏移的高精度快速计算;把最小二乘原理引入到匹配追踪(MP)算法中,克服了MP算法中寻找最优原子的耗时过程,并使用解析道和解析子波,实现了GPR信号谱分解的快速计算。然后,综合改进的相移偏移方法与最小二乘匹配追踪算法,提出了一种计算GPR偏移成像结果振幅谱和相位谱的方法,更有效地反映地下媒质的结构特征。模拟资料和实测资料的测试结果表明:相对单纯相移偏移方法,该综合方法能有效压制噪声,极大地改善含噪声资料的成像质量,而且,综合分析幅度谱和相位谱,可以提高识别和圈定目标体的能力。     

Signal Acquisition and Processing Method for Capacitive Electromagnetic Flowmeter

A kind of signal acquisition circuit and the related signal processing method of the capacitance electromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitance on the input impedance of the operational amplifier, and greatly improve the input impedance of the detection circuit to overcome the disadvantage of high signal source impedance. The rotating capacitor filter is a signal processing method based on the phase-sensitive detection technology. It can extract the weak signal from the strong and wide-band background noise, so it is very suitable for the processing of capacitive electromagnetic flow signals. Through the comparison of the signal amplitude obtained at different flow rates and the comparison of signal spectrum components before and after the filter, the effectiveness of the bootstrap signal acquisition circuit and rotating capacitor filtering method is verified.     

利用FFT校正两个密集信号的频率和相位

在一个频率分辨单元及其附近只存在一个频率信号时,对频率和初相的校正有多种方法,如三点卷积校正法、幅度比值校正法和相位差法。而在一个频率分辨单元及其附近存在两个频率信号时,上述方法均告失效。目前人们提出识别和搜索方式,但这种处理不利于快速计算。本文在分析相位差法和幅度法的基础上,给出了直接计算。仿真结果证明这一方法简单有效,而且可以推广到同一频率分辨单元存在两个以上频率信号的情况。     

光纤傅里叶变换光谱仪中谱线相位误差的乘积法校正

在光纤傅里叶变换光谱仪(FFTS)中由于抽样误差和光纤色散等原因引起相位误差导致谱线畸变.乘积法在频域实现相位误差校正,通过短双边干涉图和单边干涉图分别计算出低分辨率和高分辨率的相位谱及幅度谱,并用两个相位谱差的余弦乘以高分辨率的幅度谱得到相位误差校正的谱.讨论了两种截断函数情况下用乘积法计算得到相位误差校正后的光谱.相位校正后的谱和标准谱线比较,二者基本重合.在光纤色散存在的条件下,乘积法仍然有效地消除了谱图中相位误差,证明了FFTS中乘积法校正相位误差的有效性.该方法比双边干涉图法具有较高的光谱分辨率,光谱的基线并不会因噪声而升高,且比卷积法计算简单、速度快、实时性好,可广泛应用到FFTS中.     

压差式光纤矢量水听器驻波场校准特性研究

利用压差式光纤矢量水听器获取复声阻抗下的声场信息,不仅需对实声阻抗下声信号的相位进行校准,还必须对虚阻抗下声信号的幅度作校准。驻波场下声阻抗为虚数,可实现声信号幅度的校准,由于2个传感基元灵敏度存在差异,声压梯度值与理论值存在幅度的差异,指向性特性为一大一小的"8"字型,凹点发生偏移。采用双光纤干涉仪结构的一维压差式光纤矢量水听器进行测试,证明了上述结论,采用灵敏度修正,可将两基元灵敏度非一致对指向性造成的影响消除,得到较理想的指向性曲线,实现对声信号幅度的校准。     

面向旋翼飞机螺旋桨干扰的AM通信语音信号智能增强方法

为改善旋翼飞机空地语音通信质量,针对旋翼飞机螺旋桨造成的幅度调制(Amplitude Modulation, AM)信号复杂多频干扰以及恶劣机舱背景噪声,提出了一种通信语音时频掩膜智能增强方法,从而实现对机舱噪声与复杂干扰的有效抑制。该方法首先对原始时域语音信号进行分帧与加窗,通过短时傅里叶变换获取幅度谱与相位谱;然后将原始幅度谱作为网络输入,采用深度神经网络分析其语音信号的特征,采用长短期记忆网络挖掘语音信号的时序上下文信息,实现对语音时频掩膜的准确估计,并将其用于增强原始幅度谱以得到网络输出;最后结合原始相位谱,通过逆短时傅里叶变换获得增强后的时域语音信号。仿真与实际测试表明,该方法可有效抑制旋翼飞机环境下的干扰噪声,提高通信语音信号质量。     

An Automatic Microwave Phase Comparator

A method for passively measuring the phase angle between two signals of the same frequency is described. While simple in concept, the system has no ambiguities throughout 360/spl deg/ and is independent of relative signal amplitudes because phase angle is displayed orthogonally to amplitude. Consisting principally of two hybrids with detectors and an X-Y indicator, the system contains no moving parts or active phasing devices. In addition to making routine phase measurements, it can be readily applied to automatic direction finders, polarization analyzers, and impedance plotters.     

基于全相位频谱分析的相位差频谱校正法

为精确估计噪声背景下正弦信号频率、幅值、初始相位的真实值,结合全相位FFT与传统FFT谱分析形成了一种新的相位差频谱校正法。该法计算复杂度低,方便快捷。由两种主谱线上的谱分析结果经过简单运算即可校正出频率和幅值,而直接取主谱线上的全相位FFT相位谱值无需校正即可得到初始相位。由于全相位FFT具有抑制频谱泄漏的优良特性,因此该法适合于密集频率分布场合。该法相位估计误差非常低,无噪时处于10#61485;7分辨率级。     

频率调制光谱稳频法的信号处理算法研究

频率调制光谱稳频法利用参考气体对激光吸收量来反馈控制激光波长稳定,反馈信号的提取通过调节参考信号与吸收分量同相的方式实现.为免除移相的麻烦,提出利用吸收分量和色散分量的合成信号作为反馈信号,通过仿真证明可以利用合成信号作为反馈信号.该合成信号的提取利用两正交参考信号与合成信号耦合的方式实现,该方式方便了信号的提取,免除了调相的麻烦.最后还提出一种判定激光波长偏移的方法.     

A compensation scheme for non-ideal circuit effects in biomedical impedance sensor

The accuracy of an I/Q based biomedical impedance sensing sensor (IQBIS) suffers significantly from the PVT effects of the analog front-end, such as the amplitude errors of the stimulation signals, gain mismatches, amplitude and phase imbalances of in-phase (I) and quadrature (Q) signals, etc. These practical effects will severely impede the system performance if handled improperly. In this paper, the degradations of sensing performance by such imperfections are mathematically analyzed and quantified. Following theoretical studies, a digitally controlled correction approach is proposed to finely alleviate these impairments. The performance of the proposed scheme had been verified using Simulink and MATLAB. With the proposed error correction scheme, the accuracy is improved by at least 17 times compared to that of the typical IQBIS, for both real and imaginary values of impedance. Thus, the proposed method is very useful for IQBIS, in resisting degradation in sensing accuracies due to the process-voltage-temperature (PVT) effects.     

互阻抗精度对实现天线极低副瓣的限制

实现极低副瓣阵列天线需要作精确的互耦补偿.如果阵列的互阻抗(或互耦系数)矩阵确知,理论上可以精确补偿互耦的影响,从而实现极低副瓣接收。但无论是计算还是测量得到的互阻抗矩阵都只有一定的精度,这个精度最终决定了补偿效果。本文研究了极低副瓣阵列天线中互耦补偿对互阻抗精度的要求;推导出了互阻抗误差与通道幅相误差的关系;进而得到了互阻抗误差与副瓣电平的关系。