Control algorithm in QAM modems

Abstract

A method and apparatus for automated acquisition of a QAM signal. The method employs an embedded state machine progressing from an initial state to a final state. The method comprises the following steps: (A) Performing an automatic gain control (AGC) operation on the incoming QAM signal to maintain a steady amplitude of the QAM signal; (B) Performing a symbol timing recovery of the input QAM signal by adjusting a sampling clock of the symbol timing recovery loop; (C) Performing a Blind Equalization of the QAM signal without carrier lock to minimize a dispersion error of the received QAM signal constellation as compared with an error-free QAM signal constellation by adjusting a set of coefficients of the equalizer; (D) Performing a carrier recovery of the QAM signal to eliminate a residual carrier frequency error and to eliminate a phase error from the acquired QAM signal; and (E) Performing a decision directed equalization (DDE) of the QAM signal by updating a set of coefficients of the equalizer by using a decision based algorithm.

Description

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AI Technical Summary

Benefits of technology

The present invention relates to improving the quality of signals transmitted through communication networks such as internet or cable TV systems. More specifically, it describes a method for optimizing the performance of a specific type of modem called QAM modem. This involves several technical steps including automatically adjusting the strength of the incoming signal, restoring the proper timing of the signal's symbols, reducing distortion caused by interference between different parts of the signal, eliminating any remaining errors in the signal's carriers, and making decisions about which part of the signal should be prioritized during transmission. These improvements can lead to better overall data transfer accuracy and reliability.

Problems solved by technology

The technical problem addressed in this patent is how to improve the efficiency and accuracy of controlling a QAM modem without requiring an external digital signal processor (DSP), while also reducing latency and preventing false locks.

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