Adaptive equalizer and receiver

An adaptive equalizer comprising:

• a transversal filter having an input for receiving a signal indicative of a burst, tap-coefficients, and an output,
• a decision part having an input connected to the output of the transversal filter and an output,
• a tap-coefficient-update part that updates the tap-coefficients of said transversal filter according to a tap-coefficient-update algorithm,
• means for initializing said tap-coefficient-update part and the tap-coefficients of said transversal filter to a given state both when the burst starts and at another time during the one burst;
• and
• means for retraining said transversal filter by using a training sequence contained in the one burst.

An adaptive equalizer comprising:

• a transversal filter having an input for receiving a signal indicative of a burst, tap-coefficients, and providing an equalized output,
• a decision part having an input connected to the output of the transversal filter and an output,
• a tap-coefficient-update part that updates tap-coefficients of said transversal filter according to a tap-coefficient-update algorithm,
• means for initializing said tap-coefficient-update part and the tap-coefficients of said transversal filter a plurality of times during one burst;
• means for training said transversal filter by using a training sequence contained in the burst whereby the training sequence is equalized;
• means for making a comparison between the equalized training sequence contained in the burst and a known training sequence;
• and
• wherein said means for initializing said tap-coefficients and said means for training are operative only when there is an error in said equalized training sequence.

An adaptive equalizer comprising:

• a transversal filter having an input for receiving a signal, tap-coefficients, and an output,
• a decision part having an input connected to the output of the transversal filter and an output,
• a tap-coefficient-update part that updates the tap-coefficients of said transversal filter according to a tap-coefficient-update algorithm
• a memory for storing a received signal;
• and
• a unique word detector that effects unique word detection by using an inner product of the tap-coefficients for the unique word and the received signal stored in said memory.

An adaptive equalizer comprising:

• a transversal filter having an input for receiving a signal, tap-coefficients, and an output,
• a decision part having an input connected to the output of the transversal filter and an output,
• a tap-coefficient-update part that updates the tap-coefficients of said transversal filter according to a tap-coefficient-update algorithm;
• a memory for storing a received signal;
• a unique word detector that effects unique word detection by using the inner product of the tap-coefficients for the unique word and the received signal stored in said memory;
• means for subjecting unique word data stored in said memory to an arithmetic operation to provide phase rotations corresponding to different frequency offsets;
• unique word detection means that sends the result of said arithmetic operation to said transversal filter and effects unique word detection with respect to said unique word data;
• and
• means for estimating a frequency offset by using the result of said unique word detection and for compensating for said frequency offset.

An adaptive equalizer comprising:

• a transversal filter having an input for receiving a signal, tap-coefficients, and an output,
• a decision part having an input connected to the output of the transversal filter and an output,
• a tap-coefficient-update part that updates the tap-coefficients of said transversal filter according to a tap-coefficient-update algorithm
• a memory disposed connected to the input of said transversal filter to store a received signal;
• and
• means for estimating for each burst a frequency offset direction by using the tap-coefficients for the unique word and the received signal stored in said memory, and for detecting a frequency offset direction by averaging the frequency offset directions estimated for each burst, and for making compensation for frequency offset at a certain minute step.

A receiver comprising:

• means for quasi-coherently detecting a received signal;
• a memory for temporarily storing received data output from said quasi-coherent detection means;
• an address counter that designates a write address for said memory;
• an incoherent correlator that determines correlation between a received data pattern output from said quasi-coherent detection means and a known unique word pattern;
• means for tentatively detecting a unique word position on the basis of an output of said address counter and an output of said incoherent correlator;
• an adaptive equalizer that equalizes the received data in said memory to provide equalized data on the basis of an output of said unique word position tentative detection means;
• a unique word detector that detects a unique word pattern on the basis of said equalized data;
• and
• means for effecting frame synchronization control on the basis of an output of said unique word tentative detection means and an output of said unique word detector.

A method for receiving a signal, comprising the steps of:

• quasi-coherently detecting the signal;
• temporarily storing the detected signal in a memory;
• designating a write address for said memory;
• determining a correlation between the detected signal and a known unique word pattern;
• tentatively detecting a unique word position on the basis of the write address and said correlation;
• equalizing the detected signal in said memory to provide equalized data on the detected unique word position;
• detecting a unique word pattern on the basis of the equalized data;
• and
• effecting frame synchronization control on the basis of an the detected unique word position and the detected unique word pattern.

A method for equalizing an input signal, comprising the steps of:

• phase-rotating the input signal by (5/4).pi.;
• applying the phase-rotated input signal to an adaptive equalizer in which input data is phase rotated by -(5/4).pi.;
• and
• whereby a .pi./4 phase-rotation component is eliminated from the input signal.

A method for equalizing an input signal defining a burst having first and second parts, each part having a start and an end, comprising the steps of:

• initializing tap coefficients of a transversal filter and a tap coefficient error covariance matrix at the start of the first part of the burst;
• training the transversal filter by updating the tap coefficients of the transversal filter according to an output obtained by applying the first part of the burst to the transversal filter and the tap coefficient error covariance matrix;
• initializing the tap coefficients of the transversal filter and the tap coefficient error covariance matrix at the start of the second part of the burst;
• retraining the transversal filter by updating the tap coefficients according to an output obtained by applying the second part of the burst to the transversal filter and the tap coefficient error covariance matrix.

A method for equalizing an input signal, comprising the steps of:

• (a) training a transversal filter by updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• (b) setting the tap coefficients to most recently updated values;
• and
• (c) after the step of setting
• (i) applying the input signal to a feedforward part of the transversal filter;
• (ii) applying a known training sequence to a feedback part of the transversal filter;
• (iii) obtaining an output of the traversal filter as a result of the steps of applying;
• (iv) subjecting the output of the transversal filter to a decision to obtain an output sequence;
• and
• (v) comparing the output sequence to the known training sequence to determine whether a unique word is detected.

A method for equalizing an input signal, comprising the steps of:

• training a transversal filter by updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• applying the input signal to a feedforward part of the transversal filter;
• applying a known training sequence to a feedback part of the transversal filter;
• subjecting the output of the transversal filter to a decision;
• comparing the result of the decision to the known training sequence;
• phase-rotating the input signal in response to no detection of the unique word pattern;
• repeating the steps of applying, subjecting and comparing using the phase-rotated signal;
• and
• determining the frequency offset of the input signal.

A method for equalizing an input signal, comprising the steps of:

• training a transversal filter by updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• applying the input signal to a feedforward part of the transversal filter;
• applying a known training sequence to a feedback part of the transversal filter;
• subjecting the output of the transversal filter to a decision;
• comparing the result of the decision to the known training sequence to obtain an error vector;
• estimating a frequency offset direction using the error vector;
• and
• compensating for frequency offset in the input signal using the estimated frequency offset direction.

An adaptive equalizer for equalizing the input signal having a burst with first and second parts, comprising:

• a transversal filter having an input, an output, and a plurality of tap coefficients;
• means for initializing a tap coefficient error covariance matrix and the tap coefficients at the start of the first part of the burst;
• means for updating the tap coefficients according to both the output of the transversal filter obtained by applying the first part of the burst to the transversal filter and the tap coefficient error covariance matrix;
• means for initializing the tap coefficients and the tap coefficient error covariance matrix at the start of the second part of the burst;
• and
• means for updating the tap coefficients according to both the output of the transversal filter obtained by applying the second part of the burst to the transversal filter and the tap coefficient error covariance matrix.

An adaptive equalizer for equalizing the input signal having a burst with first and second parts, comprising:

• a transversal filter having an input, an output, and a plurality of tap coefficients;
• means for initializing a tap coefficient error covariance matrix and the tap coefficients;
• means for updating the tap coefficients in response to the output of the transversal filter obtained by applying a part of the burst to the transversal filter and the tap coefficient error covariance matrix;
• means, operative in response to the start of the first part of the burst, for operating said means for initializing and the means for updating, wherein the part of the burst applied to the transversal filter for the means for updating is the first part;
• and
• means, operative in response to the start of the second part of the burst, for operating said means for initializing and the means for updating, wherein the part of the burst applied to the transversal filter for the means for updating is the second part.

A system for equalizing an input signal, comprising:

• a transversal filter having a feedforward part, a feedback part, an input, an output, and a plurality of tap coefficients;
• means for updating the tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• means, operative after an update of the tap coefficients, for setting the tap coefficients of the transversal filter to most recently updated values;
• means, operative after the tap coefficients are set to the most recently updated values, for applying the input signal to the feedforward part of the transversal filter;
• means, operative after the tap coefficients are set to the most recently updated values, for applying a known training sequence to the feedback part of the transversal filter;
• means, operative after the tap coefficients are set to the most recently updated values, for subjecting the output of the transversal filter to a decision to obtain an output sequence;
• and
• means for comparing the output sequence to the known training sequence to determine whether a unique word is detected.

A system for equalizing the input signal, comprising:

• a transversal filter having an input, an output, and a plurality of tap coefficients;
• means for training the transversal filter by updating tap coefficients on the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• means for estimating a frequency offset direction of the input signal according to an average of frequency offset directions estimated for each burst;
• and
• means for compensating for a frequency offset in the input signal using the estimated frequency offset.

A method for receiving a signal, comprising the steps of:

• quasi-coherently detecting the signal;
• temporarily storing the detected signal in a memory;
• designating a write address for said memory;
• determining a correlation between the detected signal and a known unique word pattern using an incoherent correlator;
• tentatively detecting a unique word position by detecting a maximum value in the incoherent correlator within an aperture;
• equalizing the detected signal in said memory to provide equalized data on the detected unique word position;
• detecting a unique word pattern on the basis of the equalized data;
• and
• effecting frame synchronization control on the basis of the detected unique word position and the detected unique word pattern.

An apparatus for equalizing an input signal using a transversal filter, comprising:

• means for training the transversal filter by updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• means for applying the input signal to a feedforward part of the transversal filter;
• means for applying a known training sequence to a feedback part of the transversal filter;
• means for subjecting the output of the transversal filter to a decision;
• means for comparing the result of the decision to the known training sequence;
• means for phase-rotating the input signal in response to no detection of the unique word pattern;
• means for repeatedly operating the means for applying, means for subjecting and means for comparing using the phase-rotated signal;
• and
• means for determining the frequency offset of the input signal.

An apparatus for equalizing an input signal using a transversal filter, comprising:

• means for training the transversal filter by updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• means for applying the input signal to a feedforward part of the transversal filter;
• means for applying a known training sequence to a feedback part of the transversal filter;
• means for subjecting the output of the transversal filter to a decision;
• means for comparing the result of the decision to the known training sequence to obtain an error vector;
• means for estimating a frequency offset direction using the error vector;
• and
• means for compensating for frequency offset in the input signal using the estimated frequency offset direction.

An apparatus for equalizing an input signal, comprising:

• a transversal filter having a feedforward part, a feedback part, and tap coefficients, wherein the feedforward part has an input for receiving the input signal and wherein the feedback part has an input for receiving a known training sequence;
• means for updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• means for subjecting the output of the transversal filter to a decision;
• means for comparing the result of the decision to the known training sequence;
• means for phase-rotating the input signal in response to no detection of the unique word pattern;
• means for repeatedly operating the means for subjecting and means for comparing including means for applying the phase-rotated signal to the input of the feedforward part;
• and
• means for determining the frequency offset of the input signal.

An apparatus for equalizing an input signal, comprising:

• a transversal filter having a feedforward part, a feedback part, and tap coefficients, wherein the feedforward part has an input for receiving the input signal and wherein the feedback part has an input for receiving a known training sequence;
• means for updating tap coefficients of the transversal filter according to an output obtained by applying the input signal to the transversal filter;
• means for subjecting the output of the transversal filter to a decision;
• means for comparing the result of the decision to the known training sequence to obtain an error vector;
• means for estimating a frequency offset direction using the error vector;
• and
• means for compensating for frequency offset in the input signal using the estimated frequency offset direction.