Method and system for slicing a communication signal
A slicer can receive a communication signal having a level or amplitude that is between two discrete levels of a multilevel digital communication scheme. The slicer can compare the communication signal to a plurality of references such that multiple comparisons proceed essentially in parallel. A summation node can add the results of the comparisons to provide an output signal set to one of the discrete levels. The slicer can process the communication signal and provide the output signal on a symbol-by-symbol basis. A decision feedback equalizer (“DFE”) can comprise the slicer. A feedback circuit of the DFE can delay and scale the output signal and apply the delayed and scaled signal to the communication signal to reduce intersymbol interference (“ISI”).
1. A method for processing a multilevel communication signal comprising a series of symbol periods, each of a time duration, the method comprising the steps of:
slicing a waveform of a first symbol period in response to performing, in less time than the time duration, the steps of:
generating a first signal in response to comparing the waveform of the first symbol period to a first amplitude threshold using a first comparator disposed in a first circuit branch;
generating a second signal in response to comparing the waveform of the first symbol period to a second amplitude threshold using a second comparator disposed in a second circuit branch that is substantially parallel with the first circuit branch; and
forming a quantized signal comprising a selected level of a multilevel communication scheme for the first symbol period in response to adding the first signal to the second signal; and
compensating for intersymbol interference on a waveform of a second symbol period that immediately follows the first symbol period in response to performing the steps of:
forming a feedback signal via applying a first amount of delay and an adjustable level of gain to the formed quantized signal; and
applying the feedback signal to the waveform of the second symbol period.
2. The method of claim 1 , wherein the first amplitude threshold corresponds to a first level of the multilevel communication scheme, and wherein the second amplitude threshold corresponds to a second level of the multilevel communication scheme.
3. The method of claim 1 , wherein the slicing step further comprises the step of generating a third signal in response to comparing the waveform of the first symbol period to a third threshold using a third comparator disposed in a third circuit branch that is substantially parallel with the second circuit branch, and
wherein the step of forming the quantized signal comprises adding the first signal and the second signal to the third signal.
4. The method of claim 1 , wherein the waveform of the first symbol period has an amplitude between the selected level of the multilevel communication scheme and another level of the multilevel communication scheme,
wherein the amplitude deviates from every level of the multilevel communication scheme, and
wherein the multilevel communication scheme applies to each symbol period in the series of symbol periods.
5. The method of claim 1 , wherein using the first comparator comprises processing the waveform of the first symbol period with the first comparator, and
wherein using the second comparator comprises processing the waveform of the first symbol period with the second comparator.
6. The method of claim 1 , wherein the step of generating the first signal proceeds in parallel with the step of generating the second signal.
7. The method of claim 1 , wherein the multilevel communication scheme has at least a first level, a second level, and the selected level.
8. The method of claim 1 , wherein:
the waveform of the first symbol period is between a first level and a second level of the multilevel communication scheme and deviates from each level of the multilevel communication scheme; and
the selected level comprises one of the first level and the second level.