Pipelined decision feedback equalization in an interleaved serializer/deserializer receiver
View Patent ↗An interleaved track-and-hold front-end with multiphase clocks computes and propagates unrolled decision feedback equalization results along a pipeline with the final outputs selected from one of the interleaved previous output bits with a multiplexer operating over multiple unit intervals instead of one unit interval. An n-way interleaved serializer/deserializer utilizes an n unit interval multiplexer or n one unit interval multiplexers. Pipelined decision feedback equalization allows multiple, slower multiplexers.
1. A signal processing apparatus comprising:
a first signal pipeline comprising:
a first comparator;
a second comparator;
a first track-and-hold element configured to receive the output from the first comparator, the first track-and-hold element configured to be driven by a first clock signal;
a second track-and-hold element configured to receive the output from the second comparator, the second track-and-hold element configured to be driven by the first clock signal;
a third track-and-hold element configured to receive the output from the first track-and-hold element; and
a fourth track-and-hold element configured to receive the output from the second track-and-hold element; and
a second signal pipeline comprising:
a first comparator;
a second comparator;
a first track-and-hold element configured to receive the output from the first comparator, the first track-and-hold element configured to be driven by a second clock signal; and
a second track-and-hold element configured to receive the output from the second comparator, the second track-and-hold element configured to be driven by the second clock signal; and
a first multiplexer configured to produce one or more feedback equalized bits.
2. The signal processing apparatus of claim 1 , wherein:
the first comparator of the second signal pipeline is configured to receive the output from the first comparator of the first signal pipeline; and
the second comparator of the second signal pipeline is configured to receive the output from the second comparator of the first signal pipeline.
3. The signal processing apparatus of claim 2 , wherein:
the output from the first comparator of the first signal pipeline is scaled by a tap coefficient before it is received by the first comparator of the second signal pipeline; and
the output from the second comparator of the first signal pipeline is scaled by a tap coefficient before it is received by the second comparator of the second signal pipeline.
4. The signal processing apparatus of claim 2 , further comprising:
a third signal pipeline comprising:
a first comparator;
a second comparator;
a first track-and-hold element configured to receive the output from the first comparator, the first track-and-hold element configured to be driven by a third clock signal; and
a second track-and-hold element configured to receive the output from the second comparator, the second track-and-hold element configured to be driven by the third clock signal,
wherein:
the first signal pipeline further comprises:
a fifth track-and-hold element configured to receive the output from the third track-and-hold element; and
a sixth track-and-hold element configured to receive the output from the fourth track-and-hold element;
the second signal pipeline further comprises:
a third track-and-hold element configured to receive the output from the first track-and-hold element; and
a fourth track-and-hold element configured to receive the output from the second track-and-hold element.
5. The signal processing apparatus of claim 4 , wherein:
the first comparator of the third signal pipeline is configured to receive the output from the first comparator of the second signal pipeline; and
the second comparator of the third signal pipeline is configured to receive the output from the second comparator of the second signal pipeline.
6. The signal processing apparatus of claim 5 , wherein the first clock signal, the second clock signal and the third clock signal are substantially similar.
7. The signal processing apparatus of claim 1 , wherein:
the second signal pipeline further comprises:
a first pipeline multiplexer configured to receive the output from the first track-and-hold element and the second track-and-hold element; and
a second pipeline multiplexer configured to receive the output from the first track-and-hold element and the second track-and-hold element;
the first pipeline multiplexer of the second signal pipeline is configured to be driven by the output of the first track-and-hold element of the first signal pipeline;
the second pipeline multiplexer of the second signal pipeline is configured to be driven by the output of the second track-and-hold element of the first signal pipeline;
the first multiplexer is configured to receive outputs from the third track-and-hold element of the first signal pipeline and the fourth track-and-hold element of the first signal pipeline and produce a decision bit.
8. A communication system comprising:
a first signal pipeline comprising:
a first comparator;
a second comparator;
a first track-and-hold element configured to receive the output from the first comparator, the first track-and-hold element configured to be driven by a first clock signal;
a second track-and-hold element configured to receive the output from the second comparator, the second track-and-hold element configured to be driven by the first clock signal;
a third track-and-hold element configured to receive the output from the first track-and-hold element; and
a fourth track-and-hold element configured to receive the output from the second track-and-hold element; and
a second signal pipeline comprising:
a first comparator;
a second comparator;
a first track-and-hold element configured to receive the output from the first comparator, the first track-and-hold element configured to be driven by a second clock signal; and
a second track-and-hold element configured to receive the output from the second comparator, the second track-and-hold element configured to be driven by the second clock signal; and
a first multiplexer configured to produce one or more feedback equalized bits.
9. The communication system of claim 8 , wherein:
the first comparator of the second signal pipeline is configured to receive the output from the first comparator of the first signal pipeline; and
the second comparator of the second signal pipeline is configured to receive the output from the second comparator of the first signal pipeline.
10. The communication system of claim 9 , wherein:
the output from the first comparator of the first signal pipeline is scaled by a tap coefficient before it is received by the first comparator of the second signal pipeline; and
the output from the second comparator of the first signal pipeline is scaled by a tap coefficient before it is received by the second comparator of the second signal pipeline.
11. The communication system of claim 9 , further comprising:
a third signal pipeline comprising:
a first comparator;
a second comparator;
a first track-and-hold element configured to receive the output from the first comparator, the first track-and-hold element configured to be driven by a third clock signal; and
a second track-and-hold element configured to receive the output from the second comparator, the second track-and-hold element configured to be driven by the third clock signal,
wherein:
the first signal pipeline further comprises:
a fifth track-and-hold element configured to receive the output from the third track-and-hold element; and
a sixth track-and-hold element configured to receive the output from the fourth track-and-hold element;
the second signal pipeline further comprises:
a third track-and-hold element configured to receive the output from the first track-and-hold element; and
a fourth track-and-hold element configured to receive the output from the second track-and-hold element.
12. The communication system of claim 11 , wherein:
the first comparator of the third signal pipeline is configured to receive the output from the first comparator of the second signal pipeline; and
the second comparator of the third signal pipeline is configured to receive the output from the second comparator of the second signal pipeline.
13. The communication system of claim 12 , wherein the first clock signal, the second clock signal and the third clock signal are substantially similar.
14. The communication system of claim 8 , wherein:
the second signal pipeline further comprises:
a first pipeline multiplexer configured to receive the output from the first track-and-hold element and the second track-and-hold element; and
a second pipeline multiplexer configured to receive the output from the first track-and-hold element and the second track-and-hold element;
the first pipeline multiplexer of the second signal pipeline is configured to be driven by the output of the first track-and-hold element of the first signal pipeline;
the second pipeline multiplexer of the second signal pipeline is configured to be driven by the output of the second track-and-hold element of the first signal pipeline;
the first multiplexer is configured to receive outputs from the third track-and-hold element of the first signal pipeline and the fourth track-and-hold element of the first signal pipeline and produce a decision bit.
15. A method for decision feedback equalization comprising:
receiving a first signal pulse;
pre-computing a first possible post-decision state and second possible post decision state of the first signal pulse;
delaying the first possible post-decision state and the second possible post decision state of the first signal pulse for at least one unit interval;
receiving a second signal pulse;
pre-computing a first possible post-decision state and a second possible post decision state of the second signal pulse;
simultaneously determining a final decision state of the first signal pulse and a final decision state of the second signal pulse.
16. The method of claim 15 , further comprising:
selecting a first pipeline multiplexed decision from the first possible post-decision state and the second possible post decision state of the second signal pulse based on the first possible decision state of the first signal pulse; and
selecting a second pipeline multiplexed decision from the first possible post-decision state and the second possible post decision state of the second signal pulse based on the second possible decision state of the first signal pulse.
17. The method of claim 16 , further comprising:
delaying the first pipeline multiplexed decision for at least one time interval;
delaying the second pipeline multiplexed decision for at least one time interval; and
delaying the first possible post-decision state and the second possible post decision state of the first signal pulse for at least two unit intervals.
18. The method of claim 15 , wherein pre-computing the first possible post-decision state and the second possible post decision state of the second signal pulse comprises comparing the second signal pulse to the first possible decision state of the first signal pulse and the second possible signal state of the first signal pulse.
19. The method of claim 18 , further comprising:
receiving a third signal pulse;
pre-computing a first possible post-decision state and a second possible post decision state of the third signal pulse;
simultaneously determining a final decision state of the first signal pulse, a final decision state of the second signal pulse and a final decision state of the third signal pulse.
20. The method of claim 19 , further comprising:
selecting a third pipeline multiplexed decision from the first possible post-decision state and the second possible post decision state of the third signal pulse based on the first possible decision state of the second signal pulse; and
selecting a second pipeline multiplexed decision from the first possible post-decision state and the second possible post decision state of the third signal pulse based on the second possible decision state of the second signal pulse;
delaying the first pipeline multiplexed decision associated with the third signal pulse for at least one time interval;
delaying the second pipeline multiplexed decision associated with the third signal pulse for at least one time interval; and
delaying the first possible post-decision state and the second possible post decision state of the first signal pulse for at least three unit intervals.