David J Falconer

US Patent:

42130956, Jul 15, 1980

Filed:

Aug 4, 1978

Appl. No.:

5/931026

Inventors:

David D. Falconer - Red Bank NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H03H 740

US Classification:

375 14

Abstract:

A feedforward nonlinear signal (P(n)) is added to each sample of a linearly equalized received signal (Q(n)) to provide compensation for nonlinear intersymbol interference. The received signal is a modulated data signal impaired by linear and nonlinear distortion as well as phase jitter and additive noise. The feedforward nonlinear signal added to each sample is comprised of a weighted sum of products of individual ones of the samples and their complex conjugates. Each multiplicand bears a predetermined temporal relationship to the sample currently being processed. In an illustrative embodiment, compensation for second- and third-order intersymbol interference is provided by including two- and three-multiplicand weighted products in the feedforward nonlinear signal. Weighting coefficients for each product are adaptively updated in a decision-directed manner.

US Patent:

41818881, Jan 1, 1980

Filed:

Aug 4, 1978

Appl. No.:

5/931025

Inventors:

David D. Falconer - Red Bank NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04B 116

US Classification:

325 42

Abstract:

A receiver for a quadrature amplitude modulated data signal impaired by linear and nonlinear distortion, phase jitter and additive noise includes circuitry which compensates for these impairments. In particular, the receiver includes a processor (FIG. 1 44; FIG. 2, 44')which subtracts a feedback nonlinear signal (FIG. 1, D(n); FIG. 2, D'(n)) from each sample of the received signal, either prior or subsequent to demodulation, providing compensation for nonlinear intersymbol interference. The feedback nonlinear signal subtracted from each sample is comprised of a weighted sum of products of individual data decisions and/or the complex conjugates of data decisions, each such product, in turn, being multiplied by a predetermined harmonic of the carrier frequency. In an illustrative embodiment, compensation for second- and third-order intersymbol interference is provided by including two- and three-multiplicand weighted products in the feedback nonlinear signal. Weighting coefficients for each product are adaptively updated in a decision-directed manner.

US Patent:

39744493, Aug 10, 1976

Filed:

Mar 21, 1975

Appl. No.:

5/560576

Inventors:

David Duncan Falconer - Red Bank NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04B 116

US Classification:

325321

Abstract:

An adaptive feedforward transversal equalizer acting jointly with a data decision-directed demodulating carrier recovery system to achieve substantially jitter-free passband equalization of a suppressed-carrier coherent data signal without the use of pilot tones is improved by adding a feedback transversal filter section operating on past demodulated data symbols. The weighted output of the feedback section is subtracted from the demodulated output output of the feedforward section to provide signals from which data decisions are made and common error signals are derived. Tap-gain coefficients for both feedforward and feedback filter sections and phase angle for the demodulating carrier recovery system are adaptively updated in accordance with the common error signal. Severe frequency offset and phase jitter are simultaneously compensated.

US Patent:

45352062, Aug 13, 1985

Filed:

Jun 8, 1982

Appl. No.:

6/386224

Inventors:

David D. Falconer - Red Bank NJ

Assignee:

AT&T Bell Laboratories - Murray Hill NJ

International Classification:

H04B 324

US Classification:

1791702

Abstract:

A full-duplex, two-wire Nyquist sampled data communication system includes an adaptive echo canceller (24) at each terminal (e. g. , 10'). The echo canceller generates a replica (z. sub. m) of the echo component of each sample (r. sub. M) of the incoming signal. The replica and the sample are subtractively combined to provide an echo compensated signal (S. sub. M). During intervals of simultaneous transmission and reception, i. e. , double talk, the echo compensated signal may contain not only an uncancelled echo component but also a far-end data component. An adaptation error signal generator (80), operating in response to a stream of recovered data symbols (e. g. , a. sub. n), estimates and removes the far-end data component from the echo compensated signal and, in response to the difference, generates an adaptation error signal (. gamma. E. sub. M-D). This signal is applied as an error signal to the echo canceller. This allows the echo canceller to adapt its set of tap coefficients in response to the uncancelled echo component present in the echo compensated signal.