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Yongmin Kim - One of the best experts on this subject based on the ideXlab platform.

  • ultrasound Phase Rotation beamforming on multi core dsp
    Ultrasonics, 2014
    Co-Authors: Kerem Karadayi, Yongmin Kim, Murtaza Ali
    Abstract:

    Phase Rotation beamforming (PRBF) is a commonly-used digital receive beamforming technique. However, due to its high computational requirement, it has traditionally been supported by hardwired architectures, e.g., application-specific integrated circuits (ASICs) or more recently field-programmable gate arrays (FPGAs). In this study, we investigated the feasibility of supporting software-based PRBF on a multi-core DSP. To alleviate the high computing requirement, the analog front-end (AFE) chips integrating quadrature demodulation in addition to analog-to-digital conversion were defined and used. With these new AFE chips, only delay alignment and Phase Rotation need to be performed by DSP, substantially reducing the computational load. We implemented the delay alignment and Phase Rotation modules on a Texas Instruments C6678 DSP with 8 cores. We found it takes 200 μs to beamform 2048 samples from 64 channels using 2 cores. With 4 cores, 20 million samples can be beamformed in one second. Therefore, ADC frequencies up to 40 MHz with 2:1 decimation in AFE chips or up to 20 MHz with no decimation can be supported as long as the ADC-to-DSP I/O requirement can be met. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography. One DSP being able to handle both beamforming and back-end processing could lead to low-power and low-cost ultrasound machines, benefiting ultrasound imaging in general, particularly portable ultrasound machines.

  • software based ultrasound Phase Rotation beamforming on multi core dsp
    Internaltional Ultrasonics Symposium, 2011
    Co-Authors: Kerem Karadayi, Murtaza Ali, Yongmin Kim
    Abstract:

    Phase Rotation beamforming (PRBF) is a commonlyused digital receive beamforming technique. However, due to its high computational requirement, it has traditionally been supported by hardwired architectures (e.g., application-specific integrated circuits (ASICs) or more recently field-programmable gate arrays (FPGAs)). In this paper, we investigate the feasibility of supporting software-based PRBF on a multi-core DSP. To alleviate the high computing requirement, the analog front-end (AFE) chips integrating quadrature demodulation in addition to analog-to-digital conversion could be adopted. Under this condition, only delay alignment and Phase Rotation need to be performed by DSP, substantially reducing the computational load. We implemented the delay alignment and Phase Rotation modules on a Texas Instruments C6678 DSP with 8 cores. With a sampling rate of 40 MHz and 2:1 decimation, it takes 200 μs to generate one scanline (2048 samples/scanline) on two cores. With 4 cores, it can support beamforming for 64 channels with 10k scanlines/s, e.g., 200 scanlines/frame and at 50 frames/s. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography. Keywords-ultrasound, beamforming, Phase Rotation, DSP, programmable, software-based

  • new demodulation filter in digital Phase Rotation beamforming
    Ultrasonics, 2006
    Co-Authors: Fabio Kurt Schneider, Yangmo Yoo, A Agarwal, Liang Mong Koh, Yongmin Kim
    Abstract:

    In this paper, we present a new quadrature demodulation filter to reduce hardware complexity in digital Phase Rotation beamforming. Due to its low sensitivity to Phase delay errors, digital quadrature demodulation is commonly used in ultrasound machines. However, since it requires two lowpass filters for each channel to remove harmonics, the direct use of conventional finite impulse response (FIR) filters in ultrasound machines is computationally expensive and burdensome. In our new method, an efficient multi-stage uniform coefficient (MSUC) filter is utilized to remove harmonic components in Phase Rotation beamforming. In comparison with the directly implemented FIR (DI-FIR) and the previously-proposed signed-power-of-two FIR (SPOT-FIR) lowpass filters, the proposed MSUC filter reduces the necessary hardware resources by 93.9% and 83.9%, respectively. In simulation, the MSUC filter shows a negligible degradation in image quality. The proposed method resulted in comparable spatial and contrast resolution to the DI-FIR approach in the phantom study. These preliminary results indicate that the proposed quadrature demodulation filtering method could significantly reduce the hardware complexity in Phase Rotation beamforming while maintaining comparable image quality.

Tao Jiang - One of the best experts on this subject based on the ideXlab platform.

  • peak to average power ratio reduction in alamouti multi input multi output orthogonal frequency division multiplexing systems without side information using Phase offset based partial transmit sequence scheme
    Iet Communications, 2014
    Co-Authors: Tao Jiang, Chunxing Ni, Lili Guan, Qi Qi
    Abstract:

    In this study, a novel Phase offset-based partial transmit sequence (PTS) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in Alamouti coded multi-input-multi-output orthogonal frequency division multiplexing systems, and its key idea is that different Phase Rotation sequences are multiplied by their corresponding Phase offsets at the transmitter. Moreover, a minimum Euclidean distance decoder is proposed to recover the Phase Rotation sequences at the receiver. The theoretical analysis and simulation results show that the proposed PTS scheme could offer good performances of both the bit error rate and the PAPR reduction without transmitting the side information, resulting in the increase of the data rate.

  • peak to average power ratio reduction in alamouti multi input multi output orthogonal frequency division multiplexing systems without side information using Phase offset based partial transmit sequence scheme
    Iet Communications, 2014
    Co-Authors: Tao Jiang, Lili Guan
    Abstract:

    In this study, a novel Phase offset-based partial transmit sequence (PTS) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in Alamouti coded multi-input-multi-output orthogonal frequency division multiplexing systems, and its key idea is that different Phase Rotation sequences are multiplied by their corresponding Phase offsets at the transmitter. Moreover, a minimum Euclidean distance decoder is proposed to recover the Phase Rotation sequences at the receiver. The theoretical analysis and simulation results show that the proposed PTS scheme could offer good performances of both the bit error rate and the PAPR reduction without transmitting the side information, resulting in the increase of the data rate.

  • papr reduction of oqam ofdm signals using segmental pts scheme with low complexity
    IEEE Transactions on Broadcasting, 2014
    Co-Authors: Tao Jiang
    Abstract:

    In this paper, a novel segmental partial transmit sequence (S-PTS) scheme is proposed for the peak-to-average power ratio (PAPR) reduction in offset quadrature amplitude modulation based orthogonal frequency-division multiplexing (OQAM-OFDM) systems. The key idea of the S-PTS scheme is to divide the overlapped OQAM-OFDM signals into a number of segments, and then some disjoint subblocks are divided and multiplied with different Phase Rotation factors in each segment. Compared with the conventional PTS scheme directly employed in OQAM-OFDM sytems, the S-PTS scheme could offer better PAPR reduction with lower computational complexity.

  • a novel Phase offset slm scheme for papr reduction in alamouti mimo ofdm systems without side information
    IEEE Signal Processing Letters, 2013
    Co-Authors: Tao Jiang, Chunxing Ni, Lili Guan
    Abstract:

    In this letter, a novel Phase offset selected mapping (SLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in Alamouti coded multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, and its key idea is that different Phase Rotation sequences are multiplied by their corresponding Phase offsets at the transmitter. Moreover, a minimum Euclidian distance (MED) decoder at the receiver is proposed to recover the Phase Rotation sequences. Therefore, the proposed SLM scheme does not need to reserve bits for the transmission of side information, resulting in the increase of the data rate. Theoretical analysis and simulation results show that the proposed SLM scheme could offer good performances of both the bit error rate and PAPR reduction.

Lili Guan - One of the best experts on this subject based on the ideXlab platform.

Wei-ren Peng - One of the best experts on this subject based on the ideXlab platform.

  • analysis of laser Phase noise effect in direct detection optical ofdm transmission
    Journal of Lightwave Technology, 2010
    Co-Authors: Wei-ren Peng
    Abstract:

    In this paper, we characterize the impact of laser Phase noise (PN) in direct-detection optical OFDM (DDO-OFDM) and identify its many differences from those in coherent optical OFDM (CO-OFDM). The analytical models for the diverse PN effects, including power degradation, Phase Rotation term (PRT), and inter-carrier interference (ICI), are given in terms of critical system parameters with or without the small PN assumption. In particular, the analytical upper-bound of the ICI power with a simple form is also provided. We also present a bit error rate (BER) estimation approach which is proven to be reliable for an optical signal-to-noise-ratio (OSNR) penalty lower than ~ 2 dB. In addition, the PN tolerances, in terms of OSNR penalty, are also numerically analyzed and discussed with different QAM formats, data rates, laser linewdiths, and subcarrier numbers.

Dirk Englund - One of the best experts on this subject based on the ideXlab platform.

  • large scale uniform optical focus array generation with a Phase spatial light modulator
    Optics Letters, 2019
    Co-Authors: Donggyu Kim, Alexander Keesling, Ahmed Omran, Harry Levine, Hannes Bernien, Markus Greiner, Mikhail D Lukin, Dirk Englund
    Abstract:

    In this Letter, to the best of our knowledge, we report a new method to generate uniform large-scale optical focus arrays (LOFAs). By identifying and removing undesired Phase Rotation in the iterative Fourier transform algorithm (IFTA), our approach rapidly produces computer-generated holograms of highly uniform LOFAs. The new algorithm also shows a faster compensation of system-induced LOFA intensity inhomogeneity than the conventional IFTA. After only three adaptive correction steps, we demonstrate LOFAs consisting of O(103) optical foci with an intensity uniformity greater than 98%.

  • large scale uniform optical focus array generation with a Phase spatial light modulator
    arXiv: Optics, 2019
    Co-Authors: Donggyu Kim, Alexander Keesling, Ahmed Omran, Harry Levine, Hannes Bernien, Markus Greiner, Mikhail D Lukin, Dirk Englund
    Abstract:

    We report a new method to generate uniform large-scale optical focus arrays (LOFAs). By identifying and removing undesired Phase Rotation in the iterative Fourier-transform algorithm (IFTA), our approach rapidly produces computer-generated holograms of highly uniform LOFAs. The new algorithm also shows faster compensation of system-induced LOFA intensity inhomogeneity than the conventional IFTA. After just three adaptive correction steps, we demonstrate LOFAs consisting of $\mathcal{O}(10^3)$ optical foci with $> 98\ \%$ intensity uniformity.