Maximum likelihood sequence metric calculator

Details Maximum likelihood sequence metric calculator Maximum likelihood sequence metric calculator

1994-01-21

1995-01-24

Callahan, Timothy P.

Communications: electrical

Digital comparator systems

327 60, 327 62, 327 72, H03K 5153, G05B 100

Patent

active

053845609

ABSTRACT:
A maximum likelihood sequence metric calculator for use in a sequence decoder for processing sequences of sampled values from a communication channel or recording device. The metric calculator can be used in a maximum likelihood decoder, where the sequence can be based upon a 2-state trellis. This would include duobinary, dicode, or partial response class IV signalling. The survivor metrics for the two states is proportional to the peak amplitude detected for that state. Thus, the peak amplitude for a state is stored by a peak detector, until an opposite polarity amplitude is detected to switch the trellis path to the opposite polarity state. The path switching threshold to a state is determined by the opposite polarity state's peak amplitude and the maximum likelihood threshold value. Since only the peak amplitude of the state is stored, unbounded metric absolute value growth is not a problem.

REFERENCES:
patent: 3508158 (1970-04-01), Marchese
patent: 4710746 (1987-12-01), Shimoda et al.
patent: 4755960 (1988-07-01), Batson et al.
patent: 4991134 (1991-02-01), Ivsin
patent: 5115404 (1992-05-01), Lo et al.
Jerald Graeme, "Getting inside a peak detector to make it do the job", Electronics, Nov. 14, 1974, p. 145.
Roger Wood, "Magnetic Megabits", IEEE Spectrum, May 1990, pp. 32-38.

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