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    Efficient implementation of noise whitening post-compensation for narrowband-filtered signals
    1.
    发明授权
    Efficient implementation of noise whitening post-compensation for narrowband-filtered signals 有权

    公开(公告)号：US10826731B2

    公开(公告)日：2020-11-03

    申请号：US16146079

    申请日：2018-09-28

    申请人： Ahmed Mohamed Ibrahim Medra ,  Hossein Najafi ,  Zhuhong Zhang

    发明人： Ahmed Mohamed Ibrahim Medra ,  Hossein Najafi ,  Zhuhong Zhang

    IPC分类号： H04L25/03 ,  H04B1/10

    摘要： Apparatus and methods are provided for noise-whitening post-compensation in a receiver. A first apparatus includes a first whitening filter configured to filter a received signal comprising symbols to generate a first filtered signal. The first apparatus further includes a first decision feedback equalizer having an input coupled to an output of the first whitening filter to receive the first filtered signal. The first decision feedback equalizer is configured to apply decision feedback equalization to the first filtered signal to generate estimates for the symbols of the received signal. A second apparatus includes a decision device configured to generate a symbols decision based on a received signal comprising symbols, a noise predictor configured to predict noise in the received signal, and a subtractor configured to subtract the predicted noise from the received signal to generate a symbols estimate.

    Method and apparatus for coherent transmitter calibration
    5.
    发明授权
    Method and apparatus for coherent transmitter calibration 有权

    公开(公告)号：US11381444B2

    公开(公告)日：2022-07-05

    申请号：US17037840

    申请日：2020-09-30

    申请人： Wing Chau Ng ,  Xuefeng Tang ,  Zhuhong Zhang

    发明人： Wing Chau Ng ,  Xuefeng Tang ,  Zhuhong Zhang

    IPC分类号： H04B10/50 ,  H04B10/077 ,  H04L27/36 ,  H04L27/227 ,  H04L27/04

    摘要： Methods and apparatus for coherent transmitter calibration are provided that employ direct detection (DD) using one single photodetector (PD). The provided method and apparatus do not require hardware for coherent reception, or additional ADCs for quality control. An additional optical tone is added to a QAM optical signal that is outside the band of the QAM optical signal. The result of this is that after direct detection, there is a correlation between the real and imaginary parts, and the imaginary part can be recovered with a Hilbert transform. The estimated QAM optical signal obtained by direct detection is used to perform a transmitter factory calibration method to calibrate for one or more transmitter impairments and/or to perform in-line self-calibration.

    Fractionally spaced adaptive equalizer with non-integer sampling
    7.
    发明授权
    Fractionally spaced adaptive equalizer with non-integer sampling 有权

    公开(公告)号：US09755864B1

    公开(公告)日：2017-09-05

    申请号：US15228592

    申请日：2016-08-04

    申请人： Syed Faisal Ali Shah ,  Chuandong Li ,  Zhuhong Zhang

    发明人： Syed Faisal Ali Shah ,  Chuandong Li ,  Zhuhong Zhang

    IPC分类号： H04L25/03

    CPC分类号： H04L25/03949 ,  H04L25/03063 ,  H04L25/03885

    摘要： An apparatus for performing fractionally spaced adaptive equalization with non-integer sub-symbol sampling has an adaptive equalizer that receives a continuous stream of input data having a non-integer, fractional delay between consecutive samples at a non-integer, sub-symbol rate and outputs a stream of equalized data based on tap weights of taps of the adaptive equalizer that are spaced at an interval corresponding to the non-integer, sub-symbol rate. The tap weights are updated independently of the fractional delay between consecutive samples of the input data using an error signal. An equalizer output alignment component downstream of the adaptive equalizer aligns the stream of equalized data with a corresponding transmitted symbol.