公开(公告)号：EP0201281A3

公开(公告)日：1988-06-01

申请号：EP86303309

申请日：1986-05-01

申请人： AMERICAN TELEPHONE AND TELEGRAPH COMPANY

发明人： Debus, Walter, Jr.

IPC分类号： H03H21/00 ,  H04L25/03

CPC分类号： H03H21/0012

摘要： An adaptive equalizer 200 is disclosed which includes a plurality of multiply-accumulate devices 201, 202, 203 and a rotating coefficient register 212. Each multiply-accumulate device multiplies each input signal sample by an associated coefficient in an ensemble, stores the result and periodically outputs the accumulated results as the equalized input signal. The rotating coefficient register successively associates each coefficient in the ensemble with a different multiply-accumulate device. Coefficient update circuitry 213, 230, 214, 216, 21 is also provided which periodically updates the coefficients in the ensemble so as to optimize equalizer performance.

公开(公告)号：EP0142144A3

公开(公告)日：1988-03-16

申请号：EP84113572

申请日：1984-11-10

申请人： AMERICAN TELEPHONE AND TELEGRAPH COMPANY

发明人： Debus, Walter, Jr. ,  Siller, Curtis A., Jr.

IPC分类号： H04L25/03

CPC分类号： H04L25/03044

摘要： A fractionally spaced adaptive equalizer is disclosed wherein the coefficients (C- 2 to C+2) are updated synchronously by an integral -T error circuit (40) and alternately by a fractional -T error circuit (48). This arrangement features a single unique minimum for the adaptive structure thereby preventing the coefficient drift to very large values so coefficient tap leakage is not required to minimize coefficient values. The adaptive characteristic is well suited for linearly dispersive channels, such as exhibited during terrestrial radio transmission during tropospheric multipath propagation. The inventive principles are broadly applicable to any of the well known algorithms for adapting digital filters. A configuration of fractionally spaced equalizers (70 1 -70 4 ) provides the benefits of Nyquist-rate coefficient updating for a dual rail quadrature amplitude modulated (QAM) signal application.

公开(公告)号：EP0132988A3

公开(公告)日：1986-03-26

申请号：EP84304877

申请日：1984-07-18

申请人： AMERICAN TELEPHONE AND TELEGRAPH COMPANY

发明人： Debus, Walter, Jr. ,  Osborne, Thomas Lawrence ,  Siller, Curtis A., Jr.

IPC分类号： H04L25/497

CPC分类号： H04L25/497

摘要： A digital synthesis technique provides pulse shaping in accordance with predetermined time domain and frequency domain constraints. In the technique, the informational content of a binary bit stream is used by an access circuit (12) to form address words for accessing a read-only-memory (13). The digital representations stored in the ROM (13) represent a superposition of temporally-displaced truncated impulse time functions, each weighted by the discrete transmission symbol levels of the analog output signal. The digital representations from two ROMs (13-1 and 13-2) are toggled by a sequencing circuit. In other embodiments of the invention, different memory arrangements ranging from a single ROM (142) to an array of ROMS (163-1 through 163-3 and 164-1 through 164-3) are respectively used to decrease circuit complexity. In a digital radio transmission application of the technique, this arrangement is economical, readily reproducible and stable since it obviates the need for conventional complex analog filters.