Equalization And Decision-Directed Loops With Trellis Demodulation In High Definition TV
First Claim
1. A decision directed equalization circuit, comprising:
- a Trellis coded modulation (TCM) decoder to provide a maximum likelihood decision based on a current symbol; and
a DFE to process the maximum likelihood decision with one or more first equalization coefficients to provide a weighted maximum likelihood decision; and
a first summing junction to combine the weighted maximum likelihood decision and one or more symbol samples to provide the current symbol.
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Accused Products
Abstract
Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp. Final decisions are output from the trellis decoder to a DFE in order to enhance the DFE'"'"'s ability to operate in low SNR environments. A decision sequence estimation error signal is also generated and used to drive the tap updates of both the DFE and an FFE portion of the equalizer.
131 Citations
30 Claims
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1. A decision directed equalization circuit, comprising:
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a Trellis coded modulation (TCM) decoder to provide a maximum likelihood decision based on a current symbol; and a DFE to process the maximum likelihood decision with one or more first equalization coefficients to provide a weighted maximum likelihood decision; and a first summing junction to combine the weighted maximum likelihood decision and one or more symbol samples to provide the current symbol. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method, comprising:
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(a) providing a maximum likelihood decision based on a current symbol; and (b) processing the maximum likelihood decision with one or more first equalization coefficients to provide a weighted maximum likelihood decision; and (c) combining the weighted maximum likelihood decision and one or more symbol samples to provide the current symbol. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification