针对正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)在水声移动通信条件下存在对多普勒频偏敏感的缺陷,提出了一种基于频域变采样技术的多普勒补偿算法。利用移动通信条件下OFDM子载波正交性不变的特点,通过频域...针对正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)在水声移动通信条件下存在对多普勒频偏敏感的缺陷,提出了一种基于频域变采样技术的多普勒补偿算法。利用移动通信条件下OFDM子载波正交性不变的特点,通过频域变采样实现对多普勒的快速补偿,并采用编码反馈校验技术跟踪系统多普勒变化,达到了OFDM移动通信条件下实时通信的目的。仿真和水池实验结果证实:频域变采样多普勒补偿算法不仅可以实时地跟踪通信载体运动变化,快速补偿多普勒,同时大幅降低了时域变采样多普勒补偿算法的计算量,降低了通信系统硬件平台复杂度。展开更多
Several key techniques for a PLL-type frequency synthesizer for WLAN receivers are studied. Its structure is analyzed and the main parameters are proposed. A monolithic LC-tuned voltage controlled oscillator （LCVCO）...Several key techniques for a PLL-type frequency synthesizer for WLAN receivers are studied. Its structure is analyzed and the main parameters are proposed. A monolithic LC-tuned voltage controlled oscillator （LCVCO） with low phase noise is fabricated with TSMC 0.18μm RF （radio frequency） CMOS technology. The measured phase noise is - ll7dBc/Hz at 4MHz off the center frequency of 4. 189GHz. A down-scaling circuit with low power dissipation was fabricated in a TSMC 0.18μm mixed-signal CMOS process. The measured results show that the IC can work well under a 1.8V power supply. Its total power dissipation is only 13mW.展开更多
In order to analyze the stability impact of cooperative adaptive cruise control （CACC） platoon, an adaptive control model designed for the lead vehicle in a CACC platoon （LCACC model） in heterogeneous traffic flow...In order to analyze the stability impact of cooperative adaptive cruise control （CACC） platoon, an adaptive control model designed for the lead vehicle in a CACC platoon （LCACC model） in heterogeneous traffic flow with both CACC and manual vehicles is proposed. Considering the communication delay of a CACC platoon, a frequency-domain approach is taken to analyze the stability conditions of the novel lead-vehicle CACC model. Field trajectory data from the next-generation simulation （NGSIM） data is used as the initial condition. To account for car- following behaviors in reality, an intelligent driver model （IDM） is calibrated with the same NGSIM dataset from a previous study to model manual vehicles. The stability conditions of the proposed model are validated by the ring- road stability analysis. The ring-road test results indicate the potential of the LCACC model for improving the traffic flow stability impact of CACC platoons. Sensitivity analysis shows that the CACC fleet size has impact on the parameters of the LCACC model.展开更多
This letter deals with the frequency domain Blind Source Separation of Convolutive Mixtures (CMBSS). From the frequency representation of the "overlap and save", a Weighted General Discrete Fourier Transform...This letter deals with the frequency domain Blind Source Separation of Convolutive Mixtures (CMBSS). From the frequency representation of the "overlap and save", a Weighted General Discrete Fourier Transform (WGDFT) is derived to replace the traditional Discrete Fourier Transform (DFT). The mixing matrix on each frequency bin could be estimated more precisely from WGDFT coefficients than from DFT coefficients, which improves separation performance. Simulation results verify the validity of WGDFT for frequency domain blind source separation of convolutive mixtures.展开更多
Compared with the histogram of Discrete Cosine Transform (DCT) coefficients before the Direct Sequence Spread Spectrum (DSSS) embedding, the peak value of the histogram after the embedding decreases and expands toward...Compared with the histogram of Discrete Cosine Transform (DCT) coefficients before the Direct Sequence Spread Spectrum (DSSS) embedding, the peak value of the histogram after the embedding decreases and expands toward the border. Based on the property, an audio steganalysis of DSSS based on statistical moments of histogram is proposed. The statistical moments of the histogram in DCT domain and its frequency domain and the statistical moments of the histogram of the wavelet coefficients of every level in frequency domain are calculated as the features of classification. Support Vector Machine (SVM) is exploited as the classifier. Experimental results show that the proposed technique is effective on the DSSS embedding in DCT domain using different embedding length, and the average detection rate is 91.75%.展开更多
The authors state briefly the possibility of various simulators to handle propagation of electromagnetic waves along some interconnections, in 3D RF （Radio Frequency） circuits. The studies are first derived in the t...The authors state briefly the possibility of various simulators to handle propagation of electromagnetic waves along some interconnections, in 3D RF （Radio Frequency） circuits. The studies are first derived in the time domain： a Finite-Difference Time-Domain method is applied, taking spectra via FFTs （Fast Fourier Transform） as post-processors. Electric and magnetic field distributions, pulse propagations along stripline structures or vias are highlighted. The scattering parameters for various cases are extracted and compared. Some original issue of this work is an insight on crosstalk or shielding phenomena between lines.展开更多
A further development of exclusively inverse frequency domain method for leak detection in pipelines is presented and validated.The location and leakage can be determined by analyzing the difference of transient water...A further development of exclusively inverse frequency domain method for leak detection in pipelines is presented and validated.The location and leakage can be determined by analyzing the difference of transient water head response between the simulated and measured data in frequency domain.The transient signals are generated by portion sharp closure of a valve from the small constant opening and it needs only a few meters of water.The discrete boundary conditions and observation data are both transformed in frequency domain by Laplace transform.Example in numerical simulation is studied for demonstration of this approach.The application of the method to an experimental pipeline confirms the analysis and illustrates successful detection of the single pipeline leak.The precalibration approach is presented to minimize the effect of data and model error and it splits the method into two parts.One uses data from a known state to fit the parameters of the model and the other uses data from the current state for the fitting of leak parameters using the now calibrated model.Some important practical parameters such as wave speed,friction in steady and unsteady state and the adaptability of the method are discussed.It was found that the nonlinearity errors associated with valve boundary condition could be prevented by consideration of the induced flow perturbation curve shape.展开更多
Heart rate variability(HRV) analysis is affected by ectopic beats.An efficient method was proposed to deal with the ectopic beats.The method was based on trend correlation of the heart timing signal.Predictor of R-R i...Heart rate variability(HRV) analysis is affected by ectopic beats.An efficient method was proposed to deal with the ectopic beats.The method was based on trend correlation of the heart timing signal.Predictor of R-R interval(RRI) value at ectopic beat time was constructed by the weight calculation and the slope estimation of preceding normal RRI.The type of ectopic beat was detected and replaced by the predictor of RRI.The performance of the simulated signal after ectopic correction was tested by the standard value using power spectrum density(PSD) estimation,whereas the results of clinical data with ectopic beats were compared with the adjacent ectopic-free data.The result showed the frequency indexes after ectopy corrected had less error than other methods with the test of simulated signal and clinical data.It indicated our method could improve the PSD estimation in HRV analysis.The method had advantages of high accuracy and real time properties to recover the sinus node modulation.展开更多
文摘针对正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)在水声移动通信条件下存在对多普勒频偏敏感的缺陷,提出了一种基于频域变采样技术的多普勒补偿算法。利用移动通信条件下OFDM子载波正交性不变的特点,通过频域变采样实现对多普勒的快速补偿,并采用编码反馈校验技术跟踪系统多普勒变化,达到了OFDM移动通信条件下实时通信的目的。仿真和水池实验结果证实:频域变采样多普勒补偿算法不仅可以实时地跟踪通信载体运动变化,快速补偿多普勒,同时大幅降低了时域变采样多普勒补偿算法的计算量,降低了通信系统硬件平台复杂度。
文摘针对高分辨宽测绘带合成孔径雷达(Synthetic Aperture Radar,SAR)由斜视角空变引起的多普勒参数空变进而导致的成像性能下降的问题,提出新的多普勒参数空变解析式并给出改进的频域非线性变标(Frequency Non-Linear Chirp Scaling,FNLCS)算法。算法通过线性距离走动校正(Linear Range Walk Correction,LRWC)和梯形变换(Keystone Transform,KT)降低了回波的距离多普勒耦合,并构建了用于描述多普勒参数空变特性的距离方位频域模型,以此重新求解FNLCS算法的均衡函数和压缩函数。仿真结果表明,所提模型和算法能有效处理SAR回波的多普勒参数空变问题,获得更好的成像效果。
文摘Several key techniques for a PLL-type frequency synthesizer for WLAN receivers are studied. Its structure is analyzed and the main parameters are proposed. A monolithic LC-tuned voltage controlled oscillator （LCVCO） with low phase noise is fabricated with TSMC 0.18μm RF （radio frequency） CMOS technology. The measured phase noise is - ll7dBc/Hz at 4MHz off the center frequency of 4. 189GHz. A down-scaling circuit with low power dissipation was fabricated in a TSMC 0.18μm mixed-signal CMOS process. The measured results show that the IC can work well under a 1.8V power supply. Its total power dissipation is only 13mW.
基金The National High Technology Research and Development Program of China(863 Program)(No.2011AA110405)
文摘In order to analyze the stability impact of cooperative adaptive cruise control （CACC） platoon, an adaptive control model designed for the lead vehicle in a CACC platoon （LCACC model） in heterogeneous traffic flow with both CACC and manual vehicles is proposed. Considering the communication delay of a CACC platoon, a frequency-domain approach is taken to analyze the stability conditions of the novel lead-vehicle CACC model. Field trajectory data from the next-generation simulation （NGSIM） data is used as the initial condition. To account for car- following behaviors in reality, an intelligent driver model （IDM） is calibrated with the same NGSIM dataset from a previous study to model manual vehicles. The stability conditions of the proposed model are validated by the ring- road stability analysis. The ring-road test results indicate the potential of the LCACC model for improving the traffic flow stability impact of CACC platoons. Sensitivity analysis shows that the CACC fleet size has impact on the parameters of the LCACC model.
基金the grant from the Ph.D. Programs Foun-dation of Ministry of Education of China (No. 20060280003)the Shanghai Leading Academic Dis-cipline Project (Project No.T0102).
文摘This letter deals with the frequency domain Blind Source Separation of Convolutive Mixtures (CMBSS). From the frequency representation of the "overlap and save", a Weighted General Discrete Fourier Transform (WGDFT) is derived to replace the traditional Discrete Fourier Transform (DFT). The mixing matrix on each frequency bin could be estimated more precisely from WGDFT coefficients than from DFT coefficients, which improves separation performance. Simulation results verify the validity of WGDFT for frequency domain blind source separation of convolutive mixtures.
基金Supported by the National Natural Science Foundation of China (No.60772032)
文摘Compared with the histogram of Discrete Cosine Transform (DCT) coefficients before the Direct Sequence Spread Spectrum (DSSS) embedding, the peak value of the histogram after the embedding decreases and expands toward the border. Based on the property, an audio steganalysis of DSSS based on statistical moments of histogram is proposed. The statistical moments of the histogram in DCT domain and its frequency domain and the statistical moments of the histogram of the wavelet coefficients of every level in frequency domain are calculated as the features of classification. Support Vector Machine (SVM) is exploited as the classifier. Experimental results show that the proposed technique is effective on the DSSS embedding in DCT domain using different embedding length, and the average detection rate is 91.75%.
文摘The authors state briefly the possibility of various simulators to handle propagation of electromagnetic waves along some interconnections, in 3D RF （Radio Frequency） circuits. The studies are first derived in the time domain： a Finite-Difference Time-Domain method is applied, taking spectra via FFTs （Fast Fourier Transform） as post-processors. Electric and magnetic field distributions, pulse propagations along stripline structures or vias are highlighted. The scattering parameters for various cases are extracted and compared. Some original issue of this work is an insight on crosstalk or shielding phenomena between lines.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51109230, 50679085)the Special Funds of IWHR (Grant No. 0912)
文摘A further development of exclusively inverse frequency domain method for leak detection in pipelines is presented and validated.The location and leakage can be determined by analyzing the difference of transient water head response between the simulated and measured data in frequency domain.The transient signals are generated by portion sharp closure of a valve from the small constant opening and it needs only a few meters of water.The discrete boundary conditions and observation data are both transformed in frequency domain by Laplace transform.Example in numerical simulation is studied for demonstration of this approach.The application of the method to an experimental pipeline confirms the analysis and illustrates successful detection of the single pipeline leak.The precalibration approach is presented to minimize the effect of data and model error and it splits the method into two parts.One uses data from a known state to fit the parameters of the model and the other uses data from the current state for the fitting of leak parameters using the now calibrated model.Some important practical parameters such as wave speed,friction in steady and unsteady state and the adaptability of the method are discussed.It was found that the nonlinearity errors associated with valve boundary condition could be prevented by consideration of the induced flow perturbation curve shape.
基金Project supported by the Key Industrial Projects of Science of Zhejiang Province (No. 2007C21079)the National Key Technologies R&D Program (No. 2007BAI07A28) of China
文摘Heart rate variability(HRV) analysis is affected by ectopic beats.An efficient method was proposed to deal with the ectopic beats.The method was based on trend correlation of the heart timing signal.Predictor of R-R interval(RRI) value at ectopic beat time was constructed by the weight calculation and the slope estimation of preceding normal RRI.The type of ectopic beat was detected and replaced by the predictor of RRI.The performance of the simulated signal after ectopic correction was tested by the standard value using power spectrum density(PSD) estimation,whereas the results of clinical data with ectopic beats were compared with the adjacent ectopic-free data.The result showed the frequency indexes after ectopy corrected had less error than other methods with the test of simulated signal and clinical data.It indicated our method could improve the PSD estimation in HRV analysis.The method had advantages of high accuracy and real time properties to recover the sinus node modulation.
