公开(公告)号：US4896334A

公开(公告)日：1990-01-23

申请号：US261134

申请日：1988-10-24

Applicant: Babak Sayar

Inventor： Babak Sayar

IPC: H04B3/23 ,  H04L7/02

CPC classification number: H04L7/0062 ,  H04B3/235 ,  H04B3/238

Abstract: In a receiver for a loop interface of a digital data transmission system, a received four-level substantially randomized digital signal is sampled and a multilevel slicer compares the samples selectively with a plurality of thresholds to extract the symbols. A timing recovery circuit determines the sampling instant as a function of a precursor sample and a main pulse sample one baud apart, according to the timing function:f(t)=(1/r)h(t)-h(t-T)where 1/T is the baud rate, h(t) and h(t-T) denote the main pulse sample and precursor sample, respectively, r is the ratio between the main pulse sample and the precursor pulse sample, and t is the sampling instant. The timing recovery circuit includes: a timing estimator responsive to baud rate samples before and after slicing, respectively, for deriving a precursor estimate (z.sub.n) of the difference between the actual and desired sampling instants with reference to the ratio between the main sample pulse and the precursor sample one baud earlier; and a generator for generating a baud rate sampling clock signal signal variable in dependence upon the estimate (z.sub.n). The timing estimator derives the timing estimate z.sub.n in accordance with the expression:z.sub.n =(-1).sup.m .multidot.(a.sub.n-1 x.sub.n -a.sub.n x.sub.n-1)where m represents the magnitude bit of the 2B1Q symbol (m=0 for magnitude 1, m=1 for magnitude 3). The slicer may have three thresholds adaptable according to the magnitude of the main cursor.

Abstract translation: 在用于数字数据传输系统的环路接口的接收机中，对接收的四电平基本随机的数字信号进行采样，并且多电平限幅器选择性地将多个采样与多个阈值进行比较以提取符号。 定时恢复电路根据定时函数将采样时刻确定为前兆样本和一个波特率的主脉冲样本的函数：f（t）=（1 / r）h（t）-h（tT）其中 1 / T是波特率，h（t）和h（tT）分别表示主脉冲样本和前体样本，r是主脉冲样本和前兆脉冲样本之间的比率，t是采样时刻。 定时恢复电路包括：分别响应于在切片之前和之后的波特率样本的定时估计器，用于基于主采样脉冲和主采样脉冲之间的比率导出实际和期望采样时刻之间的差的前兆估计（zn） 前体样品前一个波特; 以及用于根据估计（zn）产生波特率采样时钟信号信号变量的发生器。 定时估计器根据以下表达式导出定时估计zn：zn =（ - 1）mx（an-1xn-anxn-1）其中m表示2B1Q符号的幅度位（对于幅度1，m = 0，m = 1为3级）。 切片器可以具有根据主光标的大小适应的三个阈值。

公开(公告)号：USRE34206E

公开(公告)日：1993-03-30

申请号：US666728

申请日：1991-03-08

Applicant: Babak Sayar

Inventor： Babak Sayar

IPC: H04L7/02

CPC classification number: H04L7/0062

Abstract: In a receiver for a loop interface of a digital data transmission system, a received four-level substantially randomized digital signal is sampled and a multilevel slicer compares the samples selectively with a plurality of thresholds to extract the symbols. A timing recovery circuit determines the sampling instant as a function of a precursor sample and a main pulse sample one baud apart, according to the timing function:f(t)=(1/r)h(t)-h(t-T)where 1/T is the baud rate, h(t) and h(t-T) denote the main pulse sample and precursor sample, respectively, r is the ratio between the main pulse sample and the precursor pulse sample, and t is the sampling instant. The timing recovery circuit includes: a timing estimator responsive to baud rate samples before and after slicing, respectively, for deriving a precursor estimate (z.sub.n) of the difference between the actual and desired sampling instants with reference to the ratio between the main sample pulse and the precursor sample one baud earlier; and a generator for generating a baud rate sampling clock signal signal variable in dependence upon the estimate (z.sub.n). The timing estimator derives the timing estimate z.sub.n in accordance with the expression:z.sub.n =(-1).sup.m.(a.sub.n-1x.sub.n -a.sub.n x.sub.n-1)where m represents the magnitude bit of the 2B1Q symbol .[.(m=0.]. (.Iadd.m=1 .Iaddend.for magnitude 1, .[.m=1.]. .Iadd.m=0 .Iaddend.for magnitude 3). The slicer may have three thresholds adaptable according to the magnitude of the main cursor.

公开(公告)号：US4995031A

公开(公告)日：1991-02-19

申请号：US368239

申请日：1989-06-19

Applicant: Sami A. H. Aly ,  Babak Sayar

Inventor： Sami A. H. Aly ,  Babak Sayar

IPC: H04B3/23 ,  H04L7/02 ,  H04L25/03 ,  H04Q11/04

CPC classification number: H04L7/0062 ,  H04B3/235 ,  H04L25/03057 ,  H04Q11/0471 ,  H04B3/238 ,  H04Q2213/19 ,  H04Q2213/214 ,  H04Q2213/36

Abstract: A receiver for a digital data transmission system comprises a sampling device for sampling digital data signals received from a subscriber loop. A precursor equalizer connected to the output of the sampling device equalizes, in effect filters, the sampled digital data signal. A timing recovery circuit connected to the output of the precursor equalizer controls the sampling device in dependence upon the filtered digital data signal. The precursor equalizer has a difference equation such that the equalized digital data signal has at least one zero-crossing occurring substantially one baud before the main cursor of each pulse. For twisted wire pair subscriber loops, the precursor equalizer may have a different equation: ##EQU1## which produces a single precursor zero-crossing. Alternatively, the precursor equalizer may have a difference equation: ##EQU2## which produces two precursor zero crossings, y(n) being the input to the filter, w(n) its output, h.sub.0 the main cursor height before equalization and h.sub.-1 the precursor height before equalization. The latter precursor equalizer may be modified by multiplying each of the coefficients (h.sub.-1 /h.sub.0).sup.2 and h.sub.-1 /h.sub.0 by a factor ##EQU3## for more precise determination of the zero crossings. A (1-Z.sup.-1) filter may be provided ahead of the precursor equalizer.

Abstract translation: 用于数字数据传输系统的接收机包括用于对从用户回路接收的数字数据信号进行采样的采样装置。 连接到采样装置的输出的前体均衡器实际上对采样的数字数据信号进行了滤波。 连接到前驱均衡器的输出的定时恢复电路根据滤波的数字数据信号控制采样装置。 前体均衡器具有差分方程，使得均衡数字数据信号在每个脉冲的主光标之前具有基本上一个波特率的至少一个过零点。 对于双绞线对用户环路，前体均衡器可以具有不同的等式：其产生单个前体零交叉。 或者，前体均衡器可以具有差分方程：其产生两个前体过零点，y（n）是滤波器的输入，w（n）其输出，h0是均衡前的主光标高度和h-1 均衡前的前体高度。 可以通过将系数（h-1 / h0）2和h-1 / h0中的每一个乘以因子“IMAGE”来修正后一前兆均衡器，以更准确地确定过零点。 可以在前体均衡器的前方设置（1-Z-1）滤波器。