Time-reversed infinite impulse response digital filtering
First Claim
1. A device for digitally filtering a digital signal, the digital signal having a group delay, wherein the device includes:
- a first memory device that sequentially stores a portion of the digital signal in a forward sequence such that a first sample within the portion is stored first within the first memory device, and a last sample within the portion is stored last within the first memory device;
a pole filter having at least one pole selected to equalize the digital signal by flattening the group delay of the digital signal, the pole filter being coupled to the first memory device, the pole filter reading the portion from the first memory device in a reverse sequence such that the last sample within the first memory device is read first from the first memory device, and the first sample within the first memory device is read last from the first memory device, wherein a time-reversed signal is generated by the first memory device in response to such reading, the time-reversed signal being filtered by the pole filter, and the pole filter generating a filtered time-reversed signal in response to the filtering of the time-reversed signal; and
a second memory device that is coupled to the pole filter and that sequentially stores the filtered time-reversed signal in the forward sequence such that a first sample within the filtered time-reversed signal is stored first within the second memory device, and a last sample within the filtered time-reversed signal is stored last within the second memory device, the second memory device generating a data signal by reading the filtered time-reversed signal in the reverse sequence such that the last signal within the second memory device is read last from the second memory device and the first sample within the second memory device is read first from the second memory device.
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Accused Products
Abstract
A digital filter includes a first memory device, a filter with at least one pole, i.e., a pole filter, coupled to the first memory device, and a second memory device coupled to the pole filter. The first memory device sequentially stores a digital signal in a forward sequence, and the pole filter sequentially reads the stored digital signal from the first memory device in a reverse sequence, thereby creating a time-reversed signal. The time-reversed signal is filtered by the pole filter, and is then stored as a filtered time-reversed signal in the second memory device in the forward sequence. A data signal is generated by the second memory device by reading the filtered time-reversed signal from the second memory device in the reverse sequence.
34 Citations
17 Claims
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1. A device for digitally filtering a digital signal, the digital signal having a group delay, wherein the device includes:
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a first memory device that sequentially stores a portion of the digital signal in a forward sequence such that a first sample within the portion is stored first within the first memory device, and a last sample within the portion is stored last within the first memory device; a pole filter having at least one pole selected to equalize the digital signal by flattening the group delay of the digital signal, the pole filter being coupled to the first memory device, the pole filter reading the portion from the first memory device in a reverse sequence such that the last sample within the first memory device is read first from the first memory device, and the first sample within the first memory device is read last from the first memory device, wherein a time-reversed signal is generated by the first memory device in response to such reading, the time-reversed signal being filtered by the pole filter, and the pole filter generating a filtered time-reversed signal in response to the filtering of the time-reversed signal; and a second memory device that is coupled to the pole filter and that sequentially stores the filtered time-reversed signal in the forward sequence such that a first sample within the filtered time-reversed signal is stored first within the second memory device, and a last sample within the filtered time-reversed signal is stored last within the second memory device, the second memory device generating a data signal by reading the filtered time-reversed signal in the reverse sequence such that the last signal within the second memory device is read last from the second memory device and the first sample within the second memory device is read first from the second memory device. - View Dependent Claims (2, 3, 4, 5)
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6. A method of digitally filtering a digital signal, the digital signal having a group delay wherein the method includes:
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(a) storing in a first memory device a portion of the digital signal in a forward sequence such that a first sample within the portion is stored first, and a last sample within the portion is stored last; (b) generating a time-reversed signal by retrieving the portion from the first memory device in a reverse sequence such that the last sample within the portion is retrieved first, and a first sample within the portion is retrieved last; (c) filtering the time-reversed signal using a pole filter having at least one pole selected to equalize the digital signal by flattening the group delay of the digital signal, and generating a filtered time-reversed signal in response to the filtering; (d) storing in a second memory device the filtered time-reversed signal in a forward sequence such that a first sample within the filtered time-reversed signal is stored first, and a last sample within the filtered time-reversed signal is stored last; and (e) generating an output signal by retrieving the filtered time-reversed signal from the second memory device in a reverse sequence such that a last sample within the filtered time-reversed signal is stored first, and a first sample within the filtered time-reversed signal is stored last. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A device for digitally filtering a digital signal, the digital signal having a group delay wherein the device includes:
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first memory means for storing a portion of the digital signal in a forward sequence such that a first sample within the portion is stored first and a last sample within the portion is stored last; first retrieving means for generating a time-reversed signal by retrieving the portion from the first memory means in a reverse sequence such that a last sample within the portion is retrieved first, and a first sample within the portion is retrieved lasts; filtering means for filtering digitally the time-reversed signal, and for generating a filtered time-reversed signal in response to the filtering, the filtering means having at least one pole selected to equalize the digital signal by flattening the group delay of the digital signal; second memory means for storing the filtered time-reversed signal in a forward sequence such that a first sample within the filtered time-reversed signal is stored first, and a last sample within the filtered time-reversed signal is stored last; and retrieving means for generating a substantially symmetric signal by retrieving the filtered time-reversed signal from the second memory means in a reverse sequence such that a last sample within the filtered time-reversed signal is stored first, and a first sample within the filtered time-reversed signal is stored last. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification