公开(公告)号：DE69225709D1

公开(公告)日：1998-07-02

申请号：DE69225709

申请日：1992-10-15

Applicant: IBM

Inventor： CHERUBINI GIOVANNI DR ,  OELCER SEDAT DR ,  UNGERBOECK GOTTFRIED DR

IPC: H04B3/14

Abstract: Adaptive analog equalizer permitting 16 Mbit/s token ring (TR) transmission over unshielded twisted-pair (UTP) cables. The equalizer (29) is located at the wiring concentrator (25), and consists of a variable and a fixed filter section. The existing TR receiver (49) and transmitter (53) remain unchanged. To compensate for distortion introduced by the cable section (19b) preceding the equalizer, the level of the signal (B) at the equalizer output (35) is used as a control criterion. The additional distortion contributed by the cable section (21a) following the equalizer is accounted for by measuring the level of the signal (D) received from the transmitter (53) of the next TR station. By these two measurements, the equalizer is adjusted such that the cable-length dependent distortion is eliminated at the next receiver (49). Transmitted Manchester-coded signals are received essentially distortion-free for cable attenuation ranging between 0 and 25 dB at 16 MHz, corresponding to zero and maximum cable lengths between TR stations. The amplification provided by equalization at the concentrator significantly mitigates also the effect of near-end crosstalk from the transmitter into the receiver input of TR stations.

公开(公告)号：DE69020568D1

公开(公告)日：1995-08-03

申请号：DE69020568

申请日：1990-10-30

Applicant: IBM

Inventor： CHERUBINI GIOVANNI DR

IPC: H04B3/14 ,  H03H15/00 ,  H03H17/00 ,  H03H21/00 ,  H04L25/03 ,  H04L27/01

Abstract: A scheme is disclosed for adapting, in a self-training procedure, an equalizer based on distributed-arithmetic design. In such an equalizer, in each modulation interval addresses are derived from stored received signal samples xq_n to choose some of the values stored in a look-up table. The chosen table values are combined by shift-and-add operations to obtain an equalizer output value yn . According to the novel adaptation scheme, only one of the chosen look-up table values is selected per modulation interval, for updating it in a particular fashion to reduce the error detected. The disclosed scheme ensures uniform selection of the stored look-up table values for updating. Only one additional shift-and-add operation is required per modulation interval to achieve satisfactory adaptation of the equalizer. No training sequence needs to be transmitted, and the scheme converges in all situations.