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US 5,668,832 AGranted
Automatic equalizer for removing inter-code interference with fading and method of controlling tap coefficients thereof
AssigneeNEC Corporation
InventorTakeshi Yamamoto
Life of this patent
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Abstract
An automatic equalizer comprises an adaptive matched filter (AMF) and a decision feedback equalizer (DFE), which is designed to stop operation of minus taps of the AMF while a demodulator is in synchronous status and to enable the minus taps of the AMF while it is in asynchronous status.
Claims4
An automatic equalizer comprising:
- a demodulator for outputting a detection signal which indicates synchronous status as well as demodulating analog base band signals from received signals;
- an analog to digital converter for converting said analog base band signals to a first digital signal string by sample-quantizing said analog base band signals;
- an adaptive matched filter for converting said first digital signal string to a second digital signal string;
- a decision feedback equalizer for equalizing intersymbol interferences in said second digital signal string and outputting a decision signal as an equalized result;
- a plurality of correlators, each of said correlators for correlating said decision signal with a signal on each tap of said adaptive matched filter;
- a plurality of integrators, each of said integrators for averaging outputs of a correlator;
- and
- a control means for multiplying an output of an integrator by a weighting coefficient based on said detection signal and outputting a result for each tap coefficient of said adaptive matched filter, for multiplying outputs of said integrators corresponding to minus taps located in an input side from a center tap of said adaptive matched filter by a weighted coefficient 0 when said detection signal indicates synchronous status, for multiplying outputs of said integrators corresponding to said minus taps by a weighting coefficient 1 when said detection signal indicates asynchronous status, and for gradually decreasing a weighting coefficient from 1 to 0 at a rate lower than the tracking rate of said decision feedback equalizer when indication of said detection signal changes to said synchronous status from said asynchronous status;
- said control means including a first selector and a second selector, each of said first and second selectors for switching output based on said detection signal, a flip-flop connected with said first selector, and a subtracter for subtracting an output of said second selector from an output of said flip-flop, said subtracter having an output, wherein:
- said first selector inputs said output of said subtracter and said output of a weighting coefficient generator, said first selector selects an output of said weighting coefficient generator when said detection signal indicates said synchronous status, and selects an output of said subtracter when said detection signal indicates said asynchronous status;
- and
- said second selector inputs a tap coefficient change amount and a value 0, selects said value 0 when said detection signal indicates said synchronous status, and selects said tap coefficient change amount when said detection signal indicates said asynchronous status.
9 more elements
An automatic equalizer comprising:
- a demodulator for outputting a detection signal which indicates synchronous status as well as demodulating analog base band signals from received signals;
- an analog to digital converter for converting said analog base band signals to a first digital signal string by sample-quantitizing said analog base band signals;
- an adaptive matched filter comprising a transversal filter having a center tap, a plurality of minus taps located in an input side from said center tap and a plurality of plus taps located in an output side from said center tap, said adaptive matched filter for converting said first digital signal string to a second digital signal string;
- a decision feedback equalizer for equalizing intersymbol interferences in said second digital signal string and outputting a decision signal as an equalized result;
- a plurality of correlators, each of said correlators for correlating said decision signal with a signal on each tap of said adaptive matched filter;
- a plurality of integrators, each of said integrators for averaging outputs of said correlator;
- and
- a control means for multiplying outputs of said integrators corresponding to said minus taps by a weighting coefficient 0 when said detection signal indicates said synchronous status, multiplying outputs of said integrators corresponding to said minus taps by a weighting coefficient 1 when said detection signal indicates a asynchronous status, and gradually decreasing a weighting coefficient from 1 to 0 at a rate lower than the tracking rate of said decision feedback equalizer when indication of said detection signal changes to said synchronous status from said asynchronous status;
- the control means including:
- a weighting coefficient generator for inputting said detection signal, said weighting coefficient having an output outputting said weighting coefficient 0 when said detection signal indicates said synchronous status and outputting said weighting coefficient 1 when said detection signal indicates said asynchronous status;
- a first selector and a second selector, each of them for switching an output based on said detection signal;
- a flip-flop connected with said first selector;
- a subtracter for subtracting an output of said second selector from an output of said flip-flop, said subtractor having an output;
- and
- a plurality of multipliers, each of said multipliers for multiplying outputs of said integrators corresponding to said minus taps by an output of said subtracter, wherein:
- said first selector inputs said output of said subtracter and said output of said weighting coefficient generator, selects an output of said weighting coefficient generator when said detection signal indicates said synchronous status, and selects said output of said subtracter when said detection signal indicates said asynchronous status;
- and
- said second selector inputs a tap coefficient change amount and a value 0, selects said value 0 when said detection signal indicates said asynchronous status, and selects said tap coefficient change amount when said detection signal indicates said asynchronous status.
15 more elements
Dependencies are inferred from the claim text.