Racal Data Communications Inc.

Aldo A Martinez

An echo canceller according to the present invention includes means for storing an impulse response in a memory, the impulse response being indicative of the characteristics of a transmission line. It also includes a detector for detecting ranges of samples within the impulse response having relatively large distribution of echo energy, these ranges of samples of relatively large distribution of echo energy being indicative of echoes on the transmission line. An echo canceller includes a digital filter having a plurality of weighted taps, each of the weighted taps having an associated tap weight value. A tap allocation circuit establishes the tap weight values in response to said detecting means so that only taps within the regions of relatively large distributions of echo energy are turned on. The ranges of echo energy are detected coarsely by detecting ranges of samples having relatively high estimated average echo power. The echo is more finely located by computing the terms analogous to the mechanical computation of the center of gravity type calculation referred to as a `center of echo` and radius of gyration type calculation referred to as `radius of echo` of the echo energy within the coarsely located ranges of samples.

Echo canceller with dynamically positioned adaptive filter taps

A data communication system, comprising a first and a second transceiver coupled together through a transmission channel, the transmission channel having transmission characteristics. A measurement circuit is coupled to the first transceiver for measuring the effects of the transmission characteristics upon a known signal transmitted from the second transceiver to the first transceiver a mapping of the transmission characteristics to a code is made and the code is transmitted from the first transceiver to the second transceiver. A plurality of predetermined filters for use in filtering signals to be transmitted by the second transceiver is selected upon receipt of the transmitted code.

Method and apparatus for equalization of data transmission system

A modem receiver having a timing recovery circuit is disclosed. The timing recovery circuit includes circuitry for extracting timing information, multiplication circuitry responsive to the timing information for providing a clock envelope signal and processing circuitry for controlling the gain of the clock envelope signal as a function of the average power of the clock envelope signal.

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Miami, FL, United States of America

Aldo A Martinez