US 3,947,768 A · Carrier-modulation data transmission equalizers

Abstract

The feature of the invention is an adaptive equalizer for modulated carrier transmission systems in which a received signal is subjected to a Hilbert transformation to obtain a second signal having a 90.degree. phase shift for all components. The two signals are then passed through a pair of filters each and the outputs are cross-combined to generate the cartesian coordinate signals of an equalized signal. The coordinate signals are combined in a polar converter and are then decoded to detect the amplitude and phase data components of the received signal. The equalizers are made adaptive by determining at each sampling time, the phase and amplitude errors in the signal and using these errors to modify the coefficients of the equalizing filters. The phase and amplitude errors are recoded into Cartesian coordinates and multiplied by the values of the samples at each tap of the filters to generate four error signals for each tap. A cross combination of these signals is time averaged and used to adjust the corresponding coefficients at the associated taps of the equalizer.

Claims11

Dependent claims

An equalization method for equalizing carrier modulated data signals transmitted through a transmission medium which introduces linear distortions into the transmitted signals, each equalization method including the steps of:

a. performing a phase transformation on the distorted received signal r(t) to obtain a signal r(t) in which the frequency components are in phase quadrature with respect to those same components of the received signal r(t);
b. performing a filtering operation on said signals r(t) and r(t), to generate two signals y(t) and y(t) representing the in phase and quadrature components of an equalized output signal, said signals being such that
y(t) = h.sub.1 (t) x r(t) - h.sub.2 (t) x r(t)
y(t) = h.sub.1 (t) x r(t) + h.sub.2 (t) x r(t)
wherein x indicates a convolution operation and h.sub.1 (t) and h.sub.2 (t) are the filtering operation impulse responses of two filters, and
c. recovering information about the phase and amplitude modulation of said modulated data signals from said equalized signal components.

3 more elements

A signal equalizing device for the receiving end of a data transmission system in which a modulated carrier is transmitted through a transmission medium which introduces linear distortions to alter a transmitted signal, said equalizer providing the in-phase and in-quadrature components of an equalized output signal and comprising:

a. a 90.degree. phase shifting means responsive to said distorted received signal to provide two signals r(t) and r(t), one of which has its frequency components shifted substantially 90.degree. from the other;
b. a pair of filtering means each responsive to one of said signals r(t) and r(t) and means for combining the outputs of said filtering means to generate the in-phase and in-quadrature components y(t) and y(t) of said equalized output signal such that
y(t) = h1(t) x r(t) - h.sub.2 (t) x r(t)
y(t) = h.sub.2 (t) x r(t) + h.sub.1 (t) x r(t)
where x represents a convolution operation and h.sub.1 (t) and h.sub.2 (t) are the impulse responses of two filters of each of said filtering means;
and
c. means responsive to said signals y(t) and y(t) to generate phase change and amplitude modulation information representative of data signals being transmitted over said medium.

4 more elements

Dependencies are inferred from the claim text.

Carrier-modulation data transmission equalizers

Life of this patent

Carrier-modulation data transmission equalizers

Life of this patent

Abstract

Claims11