公开(公告)号：US6134276A

公开(公告)日：2000-10-17

申请号：US52454

申请日：1998-03-31

申请人： Ahmad K. Aman ,  Cecil William Farrow ,  Hong Jiang ,  Agesino Primatic, Jr. ,  Charles Albert Webb, III

发明人： Ahmad K. Aman ,  Cecil William Farrow ,  Hong Jiang ,  Agesino Primatic, Jr. ,  Charles Albert Webb, III

IPC分类号： H03J7/04 ,  H03L7/091 ,  H04L7/033 ,  H04L7/04 ,  H04L27/00 ,  H04L27/06 ,  H04L27/14

CPC分类号： H04L7/046 ,  H03J7/04 ,  H03L7/091 ,  H04L27/066 ,  H04L7/0334 ,  H04L7/042 ,  H04L2027/0067 ,  H04L2027/0073 ,  H04L2027/0081

摘要： A digital timing recovery system advantageously employs both demodulated I-phase and Q-phase components to more accurately locate the synchronization signal of an incoming VSB signal. The Q-phase component is advantageously employed to detect the phase error. The use of the Q-phase component provides a more accurate measure of the phase error and results in a larger (wider) acquisition range for timing frequency offset. More specifically, the timing recovery system of this invention performs symbol clock recovery based on the VSB signal segment synchronization (sync) signal and generates a pulse density modulated (PDM) phase difference signal that controls a voltage controlled crystal oscillator (VCXO) in the phase-locked loop. This is realized, in one embodiment of the invention, by correlating received sync segment data with the known sync signal pattern and searching for "peaks" in the correlation values that are periodic at the known sync segment data rate. Once the sync pattern is found, the correlation values for adjacent samples are advantageously employed to generate the necessary feedback control signal value for the VCXO. Technical advantages of applicants' unique invention are that the need for an analog synchronous detector is eliminated, a more accurate measure than that obtained by prior known systems is obtained and a wider acquisition range is obtained for timing frequency offset.

摘要翻译： 数字定时恢复系统有利地采用解调的I相和Q相分量来更准确地定位输入的VSB信号的同步信号。 Q相分量有利地用于检测相位误差。 使用Q相分量可以更准确地测量相位误差，并导致定时频率偏移的较大（较宽）采集范围。 更具体地，本发明的定时恢复系统基于VSB信号段同步（sync）信号执行符号时钟恢复，并生成在相位上控制压控晶体振荡器（VCXO）的脉冲密度调制（PDM）相位差信号 锁定环。 在本发明的一个实施例中，通过将接收到的同步段数据与已知的同步信号模式相关并在以已知的同步段数据速率周期性的相关值中搜索“峰值”来实现。 一旦找到同步模式，有利地采用相邻采样的相关值来为VCXO生成必要的反馈控制信号值。 申请人独特发明的技术优点是消除了对模拟同步检测器的需要，获得了比现有已知系统获得的更准确的测量值，并且获得了定时频率偏移的更宽的采集范围。

公开(公告)号：US06192088B1

公开(公告)日：2001-02-20

申请号：US09052455

申请日：1998-03-31

申请人： Ahmad K. Aman ,  Cecil William Farrow ,  Hong Jiang ,  Agesino Primatic, Jr. ,  Charles Albert Webb, III

发明人： Ahmad K. Aman ,  Cecil William Farrow ,  Hong Jiang ,  Agesino Primatic, Jr. ,  Charles Albert Webb, III

IPC分类号： H04L2714

CPC分类号： H04L27/066 ,  H04L2027/0053 ,  H04L2027/0081 ,  H04L2027/0087

摘要： A digital carrier recovery system includes at least two modes of operation, namely, an acquisition mode and a tracking mode. The bandwidth of the carrier recovery loop filter is different for the acquisition mode and the tracking mode. In the acquisition mode, the digital phase-locked loop seeks and locks to the long term frequency offset of the received carrier signal. In the tracking mode, the digital phase-locked loop tracks the instantaneous variations in the carrier phase. Switching between the acquisition mode and the tracking mode is realized digitally, and includes programmable hysteresis, resulting in optimal performance in the presence of signals having high levels of phase noise (jitter). More specifically, the carrier recovery loop filter “locks” to the pilot signal of an incoming signal, e.g., a vestigial side band (VSB) video signal, by employing a so-called digital vector tracking phase-locked loop that demodulates the VSB signal. The digital vector tracking phase-locked loop includes a complex filter, i.e., a so-called vector tracking filter, that very quickly locks to the pilot signal of the passband VSB signal and once locked to the pilot signal, switches to the tracking mode that provides significantly better tracking of phase noise. The demodulation is achieved by employing a complex multiplication of the incoming signal with a complex exponential sequence to obtain an in-phase (I-phase) component and a quadrature-phase (Q-phase) component. The complex exponential sequence is generated, in one embodiment, by employing a SIN/COS look up table that is driven by a phase difference signal generated by the digital vector tracking phase-locked loop. A residual direct current (dc) component in the I-phase component caused by the pilot signal is removed, resulting in a baseband I/Q signal. A technical advantage of this carrier recovery invention is that the bandwidth of the phase-locked loop filter can be different for the acquisition mode and the tracking mode. This allows for optimal performance in both the acquisition and tracking modes of operation.

公开(公告)号：US06295325B1

公开(公告)日：2001-09-25

申请号：US09114949

申请日：1998-07-14

申请人： Cecil William Farrow ,  Daniel J. Udovic ,  Vahid Marandi ,  Mohammad Shafiul Mobin ,  Kaylan Mondal ,  Kai-Chuen Wong

发明人： Cecil William Farrow ,  Daniel J. Udovic ,  Vahid Marandi ,  Mohammad Shafiul Mobin ,  Kaylan Mondal ,  Kai-Chuen Wong

IPC分类号： H03D318

CPC分类号： H04L7/0278 ,  H04L7/0004 ,  H04L7/0025 ,  H04L7/0029

摘要： A QAM data signal timing recovery loop feedback element provides a fixed sampling time offset adjustment to two continuously variable digital rate interpolators/decimators to produce a quadrature output stream at a programmed rational rate multiple of the actual baud rate of the received data signal. The continuously variable digital rate interpolators/decimators are configured at startup so as to produce output streams at the same programmed rational rate multiple of the nominal baud rate of the anticipated received data signal, assuming the fs sample timing offset adjustment stream provided by the timing recovery feedback element to be identically 0. The “nominal” fixed sampling rate fs of the received analog input signal need not be rationally related to the nominal baud rate of the anticipated received data signal.

摘要翻译： QAM数据信号定时恢复环路反馈元件提供对两个连续可变数字速率内插器/抽取器的固定采样时间偏移调整，以按接收数据信号的实际波特率的编程有理速率倍数产生正交输出流。 假设由定时恢复提供的fs采样定时偏移调整流，启动时配置连续可变数字速率内插器/抽取器，以便产生与预期接收数据信号的额定波特率相同的编程有理数倍的输出流 反馈元件相同为0.接收的模拟输入信号的“额定”固定采样率fs不需要与预期接收数据信号的标称波特率合理相关。

公开(公告)号：US07068736B2

公开(公告)日：2006-06-27

申请号：US09902160

申请日：2001-07-11

申请人： Cecil William Farrow

发明人： Cecil William Farrow

IPC分类号： H03H7/40

CPC分类号： H03H21/0012 ,  H04L25/0305 ,  H04L2025/03687

摘要： The convergence time of a blind, adaptive equalizer is shortened by using a tracking generator. The tracking generator comprises a smoothing filter which receives and smoothes a tap coefficient error estimate derived from an output data stream. Thereafter, a fraction of the smoothed estimate is generated. It is the use of this function of the smoothes estimate which allows the convergence time to be shortened.

公开(公告)号：US07349468B2

公开(公告)日：2008-03-25

申请号：US11440168

申请日：2006-05-24

申请人： Cecil William Farrow

发明人： Cecil William Farrow

IPC分类号： H03H7/40

CPC分类号： H03H21/0012 ,  H04L25/0305 ,  H04L2025/03687

摘要： The convergence time of a blind, adaptive equalizer is shortened by using a tracking generator. The tracking generator comprises a smoothing filter which receives and smoothes a tap coefficient error estimate derived from an output data stream. Thereafter, a fraction of the smoothed estimate is generated. It is the use of this function of the smoothes estimate which allows the convergence time to be shortened.

摘要翻译： 通过使用跟踪发生器来缩短盲目自适应均衡器的收敛时间。 跟踪发生器包括平滑滤波器，其接收并平滑从输出数据流导出的抽头系数误差估计。 此后，生成平滑估计的一小部分。 使用这种平滑估计的功能可以缩短收敛时间。

公开(公告)号：US5963594A

公开(公告)日：1999-10-05

申请号：US777889

申请日：1996-12-31

申请人： Cecil William Farrow

发明人： Cecil William Farrow

IPC分类号： H03L7/085 ,  H04L7/033 ,  H03H7/30

CPC分类号： H03L7/085 ,  H04L7/033 ,  H04L7/0331 ,  H04L7/0334

摘要： A new filter that may be employed in timing recovery circuits, and automatic gain control circuits, employs a so-called vector tracking filter (VTF). The VTF includes a complex filter with a time constant so long that it might be considered a leaky integrator. In operation, the VTF builds up an average vector (timing (gain) estimate vector) having a direction that is the average of the estimated timing (gain) error, which is stored in the VTF. When the VTF is employed in an automatic gain control arrangement, the vector becomes a scalor and only the amplitude is tracked. When an arbitrary timing (gain) correction is made, to the incoming signal, this causes a rotation of the timing (gain) estimate vector. In order to track this rotation, a comparable rotation is made to the stored timing (gain) estimate vector. This allows the stored timing (gain) estimate vector to build up, and at any time the stored timing (gain) estimate vector will be the same as if the current incoming phase had been constant for all previous time. Consequently, it is possible to use a very long time constant in the VTF for long-term steady timing (gain) and at the same time acquire timing (gain) fast. In one example, the length of the vector stored in the VTF is allowed to build up until it reaches the mean value of the incoming timing (gain) estimate.

摘要翻译： 可用于定时恢复电路和自动增益控制电路的新型滤波器采用所谓的矢量跟踪滤波器（VTF）。 VTF包括一个时间常数长的复杂滤波器，可以认为是一个泄漏积分器。 在操作中，VTF建立一个平均矢量（定时（增益）估计向量），其具有存储在VTF中的作为估计定时（增益）误差的平均值的方向。 当在自动增益控制装置中使用VTF时，矢量变为定标器，并且仅跟踪振幅。 当进行任意定时（增益）校正时，对于输入信号，这导致定时（增益）估计向量的旋转。 为了跟踪该旋转，对存储的定时（增益）估计向量进行相当的旋转。 这允许所存储的定时（增益）估计向量建立，并且在任何时间存储的定时（增益）估计向量将与当前进入阶段对于所有先前时间都是恒定的相同。 因此，可以在VTF中使用非常长的时间常数用于长期稳定定时（增益），并且同时快速地获取定时（增益）。 在一个示例中，允许存储在VTF中的矢量的长度建立直到达到输入定时（增益）估计的平均值。

公开(公告)号：US06359519B1

公开(公告)日：2002-03-19

申请号：US09502138

申请日：2000-02-11

申请人： Cecil William Farrow

发明人： Cecil William Farrow

IPC分类号： H03B524

CPC分类号： H03L7/0997 ,  H03K3/0315 ,  H03L7/091

摘要： A method and apparatus are disclosed for numerically controlling a ring oscillator. The disclosed programmable period ring oscillator selectively switches pairs of inverters into or out of the ring oscillator to provide a desired frequency. In one implementation, a programmable period ring oscillator provides a range of five to nine inverters that may selectively be included in the ring oscillator in increments of two inverters. A frequency synthesizer is disclosed that aligns the phase of the programmable ring oscillator with a reference signal. The frequency synthesizer generates a phase difference signal that is that is representative of the phase difference between the reference signal and the ring oscillator output. The phase difference signal is utilized to correct the frequency of the ring oscillator, so that the mean phase of the ring oscillator corresponds to the mean phase of the reference signal. The state of all of the stages in the ring oscillator are sampled, to permit the phase of the ring oscillator to be measured to a fraction of one cycle.

摘要翻译： 公开了用于数字控制环形振荡器的方法和装置。 所公开的可编程周期环形振荡器选择性地将成对的反相器转换成环形振荡器或从环形振荡器输出以提供期望的频率。 在一个实现中，可编程周期环形振荡器提供可以选择性地以两个反相器的增量包括在环形振荡器中的五到九个反相器的范围。 公开了一种频率合成器，其将可编程环形振荡器的相位与参考信号对准。 频率合成器产生表示参考信号和环形振荡器输出之间的相位差的相位差信号。 相位差信号用于校正环形振荡器的频率，使得环形振荡器的平均相位对应于参考信号的平均相位。 对环形振荡器中的所有级的状态进行采样，以允许将环形振荡器的相位测量到一个周期的几分之一。

公开(公告)号：US06282248B1

公开(公告)日：2001-08-28

申请号：US09114948

申请日：1998-07-14

申请人： Cecil William Farrow ,  Daniel Udovic ,  Kalavai Janardhan Raghunath

发明人： Cecil William Farrow ,  Daniel Udovic ,  Kalavai Janardhan Raghunath

IPC分类号： H04L2714

CPC分类号： H04L7/0029 ,  H04L27/38

摘要： A method of efficiently demodulating and isolating a signal within a fixed possibly wider band spectral region, having any of a wide range of baud rates. The signal is sampled at a fixed, first frequency which remains fixed no matter what the baud rate. Thus, the sample rate does not necessarily correspond to the desired baud rate. The sampled signal is then demodulated and low pass filtered to create baseband samples at the first frequency, which are then subject to user-specified arbitrary rate change in a continuously variable interpolator/decimator (continuously variable digital delay (CVDD) device), and decimated by a programmable power of 2, to produce samples at a second frequency. The second frequency is preferably determined to be a whole number multiple of the desired baud rate, e.g., twice the desired baud rate. The samples are equalized to produce output symbols at the target baud rate. Based on this method, a demodulator can receive signals of varying bandwidth and baud rates at arbitrary spectral locations within a possibly wider bandwidth aggregate channel span, and can adapt its target baud rate for each signal to be the actual baud rate of the derived incoming data signal within the possibly wider bandwidth aggregate channel span.

摘要翻译： 一种有效地解调和隔离固定的可能更宽的频带光谱区域内的信号的方法，其具有宽的波特率范围。 信号以固定的第一频率进行采样，无论波特率如何，都保持固定。 因此，采样率不一定对应于所需的波特率。 然后对采样信号进行解调和低通滤波，以便在第一个频率产生基带采样，然后在连续可变的内插器/抽取器（连续可变数字延迟（CVDD）器件）中进行用户指定的任意速率变化），并将其抽取 通过2的可编程功率，以第二频率产生样本。 优选地将第二频率确定为所需波特率的整数倍，例如所需波特率的两倍。 样本相等，以目标波特率产生输出符号。 基于这种方法，解调器可以在可能更宽的带宽聚合信道跨度内的任意频谱位置接收不同带宽和波特率的信号，并且可以使其每个信号的目标波特率适应为导出的输入数据的实际波特率 信号在可能更宽的带宽聚合信道跨度内。

公开(公告)号：US06772022B1

公开(公告)日：2004-08-03

申请号：US09335277

申请日：1999-06-17

申请人： Cecil William Farrow ,  Yhean-Sen Lai ,  Kannan Rajamani

发明人： Cecil William Farrow ,  Yhean-Sen Lai ,  Kannan Rajamani

IPC分类号： G06F1700

CPC分类号： G10L19/022

摘要： A method of converting between a sampling rate associated with a first audio format and a second audio format includes up-sampling an input signal sampled at the sample rate associated with the first audio format. Then, the up-sampled signal is filtered as a function of a fractional delay to generate an output signal sampled at the sample rate associated with the second audio format. The fractional delay is computed from the sample rates associated with the first and second audio formats. In one embodiment, the sample rates that are converted between are associated with a compact disc format having a sample rate of about 44.1 kHz and a digital audio tape format having a sample rate of about 48 kHz. In such case, the input samples are preferably up-sampled by a factor of two and the samples are then preferably filtered in accordance with a third order six taps coefficient finite impulse response filtering technique. The methodology of the present invention permits sample rate conversion from the CD format to the DAT format and from the DAT format to the CD format without changing filter coefficients.

摘要翻译： 在与第一音频格式相关联的采样率和第二音频格式之间转换的方法包括对与第一音频格式相关联的采样率采样的输入信号进行上采样。 然后，上采样信号作为分数延迟的函数进行滤波，以产生以与第二音频格式相关联的采样率采样的输出信号。 从与第一和第二音频格式相关联的采样率计算分数延迟。 在一个实施例中，在其之间转换的采样率与具有约44.1kHz的采样率的压缩光盘格式和具有约48kHz的采样率的数字音频磁带格式相关联。 在这种情况下，输入采样优选地以2倍上采样，然后优选地根据三阶六抽头系数有限脉冲响应滤波技术对采样进行滤波。 本发明的方法允许从CD格式到DAT格式和从DAT格式到CD格式的采样率转换，而不改变滤波器系数。

公开(公告)号：US5870442A

公开(公告)日：1999-02-09

申请号：US777893

申请日：1996-12-31

申请人： Cecil William Farrow

发明人： Cecil William Farrow

IPC分类号： H04L7/027 ,  H04L7/033 ,  H04L27/06

CPC分类号： H04L7/027 ,  H04L7/033

摘要： Timing recovery circuits, automatic gain control circuits and the like, employ a so-called vector tracking filter (VTF) in conjunction with other timing recovery techniques. The VTF includes a complex filter with a time constant so long that it might be considered a leaky integrator. In operation, the VTF builds up an average vector (timing (gain estimate vector) having a direction that is the average of the estimated timing (gain) error, which is stored in the VTF. When an arbitrary timing (gain) correction is made, to the incoming signal, this causes a rotation of the timing (gain) estimate vector. In order to track this rotation, a comparable rotation is made to the stored timing (gain) estimate vector. This allows the stored timing (gain) estimate vector to build up, and at any time the stored timing (gain) estimate vector will be the same as if the current incoming phase had been constant for all previous time. Consequently, it is possible to use a very long time constant in the VTF for long-term steady timing (gain) and at the same time acquire timing (gain) fast. In one example, the length of the vector stored in the VTF is allowed to build up until it reaches the mean value of the incoming timing (gain) estimate.

摘要翻译： 定时恢复电路，自动增益控制电路等采用所谓的矢量跟踪滤波器（VTF）结合其他定时恢复技术。 VTF包括一个时间常数长的复杂滤波器，可以认为是一个泄漏积分器。 在操作中，VTF建立平均矢量（定时（增益估计向量）），其具有存储在VTF中的估计定时（增益）误差的平均值的方向，当进行任意定时（增益）校正时 对于输入信号，这导致定时（增益）估计向量的旋转，为了跟踪该旋转，对存储的定时（增益）估计向量进行相当的旋转，这允许存储的定时（增益）估计 向量建立，并且在任何时候，所存储的定时（增益）估计向量将与当前进入阶段对于所有先前时间都是恒定的相同，因此可以在VTF中使用非常长的时间常数 对于长期稳定的定时（增益），并且同时快速地获取定时（增益），在一个示例中，允许存储在VTF中的向量的长度建立直到其达到进入定时的平均值 收益）估计。