Method and apparatus for channel equalization
AssigneeSolarflare Communications, Inc.
InventorsWilliam W. Jones, George A. Zimmerman
Life of this patent
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Abstract
A method and apparatus is disclosed to overcome the effects of intersymbol interference during data transmission. Overcoming the effects of intersymbol interference makes possible higher data transmission rates for a given error rate. In one embodiment a receiver processing system a first, second and third filter, such that the second and third filter comprise feedback filters. Filter coefficients are calculated to reduce the undesirable effects of the channel, such as intersymbol interference. A training process occurs to establish the first filter as a mixed phase filter and the third filter as minimum phase filter. The second filter is configured based on the transfer function of the channel and one or more coefficients may be set to a predetermined value.
Claims20
A system for channel equalization comprising:
- a first filter configured to utilize one or more first filter coefficients, the first filter comprising mixed phase filter and configured to output a first filter output;
- a second filter having one or more second filter coefficients based on the transfer function of the channel, the second filter configured to filter an error signal and output a filtered error signal;
- and
- a third filter comprising a feedback filter having one or more third filter coefficients, the third filter comprising a minimum phase filter and is configured to output a third filter output;
- a first junction configured to subtract the filtered error signal and the third filter output from the first filter output to create a decision device input;
- a decision device configured to receive the decision device input and create a decision device output;
- and
- a second junction configured to create the error signal based on the decision device input and the decision device output, wherein the first, second, and third filters are located in a receiver.
A method of equalizing a received signal comprising:
- receiving a signal;
- filtering the received signal with a feed forward filter, the first filter configured as a mixed phase filter, to create a filtered signal;
- subtracting a first feedback signal and a second feedback signal from the filtered signal to create a decision device input signal;
- performing a decision operation on the decision device input signal to create a output signal;
- creating a difference signal comprising the difference between the decision device input signal and the output signal;
- filtering the difference signal with a feedback filter configured as a minimum phase filter to create the first feedback signal;
- and
- filtering the output signal with a feedback filter configured with coefficients based on the transfer function of the channel to create the second feedback signal.
A receiver configured to process a received signal comprising;
- at least one analog front end configured to receive an incoming signal and convert the incoming signal to a digital format;
- at least one feedforward filter configured as a mixed phase filter to filter the incoming signal in a digital format to create a filtered signal;
- at least one junction configured to combine the filtered signal with two or more feedback cancellation signals to create a junction output;
- two or more filters configured to generate the two or more feedback cancellation;
- signals, wherein one of the two or more filters is a minimum phase filter and the other is based on the transfer function of the channel;
- a decision device configured to receive a decision device input and perform a decision operation to create an decision device output;
- wherein at least one of the two or more filters receives and filters a difference signal comprising the difference between the decision device input and the decision device output.
Dependencies are inferred from the claim text.