Daniel A Ray

US Patent:

52672697, Nov 30, 1993

Filed:

Sep 4, 1991

Appl. No.:

7/754604

Inventors:

Cheng-chung Shih - Rancho Cordova CA
Haim Shafir - Sacramento CA
Stefan M. Wurster - El Dorado Hills CA
Cecil Aswell - Orangevale CA
Daniel L. Ray - Fair Oaks CA
Joseph E. Heideman - Orangevale CA

Assignee:

Level One Communications, Inc. - Folsom CA

International Classification:

H04L 2549

US Classification:

375 60

Abstract:

A data communication system employing predetermined equalized waveforms for transmit equalization is disclosed. Serial NRZ data is received from a network controller and utilized to select from memory its equivalent as predistorted and filtered Manchester encoded data. Predetermined waveforms in memory are representative of the analog waveform produced when predistorted digital Manchester encoded data is passed through a high order transmit filter. Data from memory drives a digital to analog converter (DAC) to reconstruct the waveforms into analog form. A line driver having an integrated single pole low pass filter impresses the equalized waveform on to the transmission line.

US Patent:

55815855, Dec 3, 1996

Filed:

Oct 21, 1994

Appl. No.:

8/327184

Inventors:

Hiroshi Takatori - Sacramento CA
Daniel L. Ray - Sacramento CA
Kenneth G. Buttle - Orangevale CA
James W. Everitt - Grass Valley CA

Assignee:

Level One Communications, Inc. - Sacramento CA

International Classification:

H03H 730
H04L 700
H03D 324

US Classification:

375376

Abstract:

A timing recovery apparatus for recovering the timing from sparse timing information in multi-level or partial response codes. The timing recovery apparatus includes a switch for sampling an incoming line code signal according to a selectable sample rate, a feed forward equalizer for filtering the sampled signal, a decision feedback equalizer for cancelling intersymbol interference in the filtered signal and for recovering the timing in the sampled signal. The timing recovery circuit creates a phase correction signal in response to a signal received from the feed forward equalizer and thereby control the sample rate of the sample switch so that the signal-to-noise ratio at the node before the decision is maximized. The voltage controlled crystal oscillator may be controlled within a certain frequency range by using a second phase detector which compares the phase of the signal controlling the sampling of the incoming line code with a reference clock.