Mitsubishi Denki Kabushiki Kaisha

Mari Matsunaga

Toshiharu Kojima

Takashi Asahara

A demodulator in a receiver has a multiple symbol differential phase detector which calculates phase differences between a received signal and received signals of 1, 2, . . . , N (Where N is an integer greater than 2) before so as to output the calculated results as N symbol differential phase detected signals. Further, a soft decision sequence estimating unit in this demodulator estimates a transmitted differential phase sequence according to the 1, 2, . . . , N symbol differential phase detected signals using a trellis diagram representing transitions of differential phase states of a transmitted signal and Viterbi algorithm and estimates soft decision demodulated data according to estimated transmitted differential phase sequence and the survival path metrics that transit into each state on the trellis diagram.

Demodulator, receiver, and communication system

A phase region deciding unit decides the phase region in which the signal point falls and a counter unit counts the number of signal points in each phase region. A weighted average calculating unit calculates a weighted average using the previous weighted average and a result of counting in the counter unit. A likelihood calculating unit calculates likelihood of the weighted average of phase distribution calculated weighted average using the phase-distribution table stored in a phase-distribution table storing unit for each phase-distribution model, detects a maximum likelihood phase-distribution model, and outputs the signal quality corresponding to the detected phase-distribution model as the estimated signal quality.

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Tokyo, Japan

Mari Matsunaga