Compensating for distortion in a communication channel
AssigneeSicom, Inc.
InventorsRonald D. McCallister, Daniel D. Shearer, III
Life of this patent
Estimating the term…
Abstract
This disclosure relates to a technique for estimating the characteristics of a propagation channel by processing a cyclostationary signal which has passed through it. The technique extends to the use of this estimate to reduce the impact of the channel distortion on the recovered signal. Unique features of this technique include its ability to function even when strong interference is present with the cyclostationary signal of interest.
Claims63
In the method of estimating transfer characteristics of a propagation medium from a cyclostationary signal received therefrom comprising the steps of:
- generating a plurality of estimator signals only from the received cyclostationary signal, each of which is representative of a spectrally discrete portion of a correlation of said received signal;
- and
- using said plurality of estimator signals to provide an estimate of the transfer characteristics of the medium.
Apparatus for providing an estimate of transfer characteristics of a propagation medium from a cyclostationary signal received therefrom comprising, in combination:
- means for generating a plurality of estimator signals only from the received cyclostationary signal, each of which is representative of a spectrally discrete portion of a correlation of said received signal;
- and
- means for using said plurality of estimator signals to provide an estimate of the transfer characteristics of the medium.
In the method of recovering a baseband signal from a spread spectrum signal received from a propagation medium, said spread spectrum signal being generated by modulating the baseband signal with a reference spreading signal, the steps of:
- generating a plurality of estimator signals, each of which is representative of a spectrally discrete portion of a correlation of said received signal;
- providing a representation of an assumed set of values of coefficients of an equation of the transfer function of a model that is an estimate of the transfer characteristics of the medium;
- generating a plurality of model signals, respectively corresponding to said estimator signals, in accordance with a relationship between a discrete portion of the correlation of the output of said model and the transfer function of said model;
- iteratively adjusting said values to reduce differences between said estimator signals and said respectively corresponding model signals;
- and
- providing a local spreading signal synchronized to said reference spreading signal, that is modified in accordance with the estimated transfer function.
A matched filter for received spread signals that are demodulated by sequences provided by first and second spread sequence generators, respectively, to provide first and second spread baseband signals, said sequences being of the same chip rate but differing from each other, comprising:
- generating means for providing an in-phase RF carrier signal and a quadrature RF carrier signal that are phase shifted 90.degree. from each other;
- means for downconverting said received spread signals with said in-phase and quadrature RF signals, respectively, to provide a pair of first and second baseband spread spectrum signals, said downconverting means being adapted for coupling to a medium through which said received spread spectrum signals are propagated;
- estimating means coupled to said medium for generating a representation of the coefficients of an equation of a model of the transfer characteristics of said medium;
- simulation means for providing first and second spreading signals that are modified by said model;
- and
- recovery means for providing first and second recovered baseband signals in response to said spreading signals and said first and second baseband spread spectrum signals.
Dependencies are inferred from the claim text.