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Frédéric Patat - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of the blood Doppler Frequency Shift by a time-varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    – Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency estimate is illustrated on both simulated and in vivo Doppler signals.

  • estimation of the blood Doppler Frequency Shift by a time varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency estimate is illustrated for both simulated and in vivo Doppler signals.

Jean-marc Girault - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of the blood Doppler Frequency Shift by a time-varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    – Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency estimate is illustrated on both simulated and in vivo Doppler signals.

  • estimation of the blood Doppler Frequency Shift by a time varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency estimate is illustrated for both simulated and in vivo Doppler signals.

Denis Kouamé - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of the blood Doppler Frequency Shift by a time-varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    – Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency estimate is illustrated on both simulated and in vivo Doppler signals.

  • estimation of the blood Doppler Frequency Shift by a time varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency estimate is illustrated for both simulated and in vivo Doppler signals.

Abdeldjalil Ouahabi - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of the blood Doppler Frequency Shift by a time-varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    – Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency estimate is illustrated on both simulated and in vivo Doppler signals.

  • estimation of the blood Doppler Frequency Shift by a time varying parametric approach
    Ultrasonics, 2000
    Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric Patat
    Abstract:

    Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency Shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency estimate is illustrated for both simulated and in vivo Doppler signals.

Xihua Zou - One of the best experts on this subject based on the ideXlab platform.

  • photonic approach for simultaneous measurements of Doppler Frequency Shift and angle of arrival of microwave signals
    Optics Express, 2019
    Co-Authors: Lianshan Yan, Xia Feng, Xihua Zou, Wei Pan, Tao Zhou, Bin Luo, Zhiyu Chen
    Abstract:

    A photonic method used to simultaneously measure the Doppler-Frequency-Shift (DFS) and angle-of-arrival (AOA) of microwave signals is proposed and experimentally demonstrated. At the remote antenna unit (RAU), the local oscillator (LO) signal and two echo signals are applied to a phase modulator (PM) and a polarization-division-multiplexed Mach-Zehnder modulator (PDM-MZM), respectively. After transmission over a fiber link, the DFS and AOA parameters can be obtained by processing the two low-Frequency electrical signals at the central office (CO). Experimental results show that the DFS between ± 100-kHz with < ± 5 × 10−3-Hz error and the AOA from 1.82° to 90° with <0.85° error at 10 GHz are obtained over a 10-km single mode fiber (SMF) transmission. Moreover, the DFS direction can also be distinguished by comparing the phase difference of two electrical signals.

  • Photonic approach for simultaneous measurements of Doppler-Frequency-Shift and angle-of-arrival of microwave signals.
    Optics Express, 2019
    Co-Authors: Lianshan Yan, Xia Feng, Xihua Zou, Wei Pan, Bin Luo, Zhou Tao, Zhiyu Chen
    Abstract:

    A photonic method used to simultaneously measure the Doppler-Frequency-Shift (DFS) and angle-of-arrival (AOA) of microwave signals is proposed and experimentally demonstrated. At the remote antenna unit (RAU), the local oscillator (LO) signal and two echo signals are applied to a phase modulator (PM) and a polarization-division-multiplexed Mach-Zehnder modulator (PDM-MZM), respectively. After transmission over a fiber link, the DFS and AOA parameters can be obtained by processing the two low-Frequency electrical signals at the central office (CO). Experimental results show that the DFS between ± 100-kHz with < ± 5 × 10−3-Hz error and the AOA from 1.82° to 90° with

  • OFC - Simultaneous Measurements of Doppler-Frequency-Shift and Angle-of-Arrival of Microwave Signals Based on Polarization-Diversified Heterodyning
    Optical Fiber Communication Conference (OFC) 2019, 2019
    Co-Authors: Lianshan Yan, Xia Feng, Xihua Zou, Wei Pan, Tao Zhou, Zhiyu Chen
    Abstract:

    Simultaneous measurements of the Doppler-Frequency-Shift (DFS) and angle-of-arrival (AOA) of microwave signals is proposed. DFS between ±100-KHz with

  • Wideband Microwave Doppler Frequency Shift Measurement and Direction Discrimination Using Photonic I/Q Detection
    Journal of Lightwave Technology, 2016
    Co-Authors: Bing Lu, Lianshan Yan, Xihua Zou, Wei Pan, Yan Pan, Xinkai Liu, Bin Luo
    Abstract:

    An enhanced approach to realizing wideband microwave Doppler Frequency Shift (DFS) measurement and direction discrimination based on photonic in-phase and quadrature coherent detection is proposed and demonstrated experimentally. In the proposed approach, the DFS between the transmitted microwave signal and the received echo signal is converted into two quadrature low-Frequency electrical signals through the coherent detection by using an optical hybrid and two balanced photodetectors. The microwave DFS of interest can be estimated with an unambiguous direction, and in particular with a greatly improved resolution. Meanwhile, photonic coherent and balanced detection effectively eliminates the optical signal to signal beating interferences. In the proof-of-concept experiment, the DFSs from -90 to +90 kHz are successfully estimated for microwave signals at 10, 14, 18, and 38 GHz. The measurement errors are estimated to be less than ±5.8 Hz which are an order of magnitude lower than those (i.e., ±60 Hz) released before. Such results provide a high resolution for radial velocity measurement as well. In addition, the performance of the proposed approach in term of the signal-to-noise ratio and stability is discussed.

  • wideband Doppler Frequency Shift measurement and direction ambiguity resolution using optical Frequency Shift and optical heterodyning
    Optics Letters, 2015
    Co-Authors: Xihua Zou, I Luo
    Abstract:

    A photonic approach for both wideband Doppler Frequency Shift (DFS) measurement and direction ambiguity resolution is proposed and experimentally demonstrated. In the proposed approach, a light wave from a laser diode is split into two paths. In one path, the DFS information is converted into an optical sideband close to the optical carrier by using two cascaded electro-optic modulators, while in the other path, the optical carrier is up-Shifted by a specific value (e.g., from several MHz to hundreds of MHz) using an optical-Frequency Shift module. Then the optical signals from the two paths are combined and detected by a low-speed photodetector (PD), generating a low-Frequency electronic signal. Through a subtraction between the specific optical Frequency Shift and the measured Frequency of the low-Frequency signal, the value of DFS is estimated from the derived absolute value, and the direction ambiguity is resolved from the derived sign (i.e., + or -). In the proof-of-concept experiments, DFSs from -90 to 90 kHz are successfully estimated for microwave signals at 10, 15, and 20 GHz, where the estimation errors are lower than ±60  Hz. The estimation errors can be further reduced via the use of a more stable optical Frequency Shift module.