Convolutionally-encoded quadrature frequency-modulation system

Details Convolutionally-encoded quadrature frequency-modulation system Convolutionally-encoded quadrature frequency-modulation system

1991-04-26

1992-12-22

Kuntz, Curtis

Pulse or digital communications

Repeaters

Testing

341 43, 375 18, H04L 2534

Patent

active

051739267

ABSTRACT:
A convolutionally-encoded quadrature frequency-modulation (CQFM) system of the present invention is a digital modulation system in which binary source data is encoded by a convolutional encoder with an encoding rate of r=1/2, quaternarized, and is then fed into a duobinary converter and a mod.4 mapper for subsequent quadrature frequency-modulation with a modulation index of h=1. The system has a soft-decision Viterbi decoder. This decoder has not only a symbol-metric calculator, a state-metric memory, a path-history memory, and ACS circuit, all used in an ordinary Viterbi decoding system, but also a signal location pointer, which is a memory indicating any one of the nominal signal points in a two-dimensional signal space and being updated in response to the selection of higher-likelihood by the ACS circuit. The soft-decision Viterbi decoder is able to decode data bits at a time by tracking trajectories of the transition between the states of the whole including the encoder and the duobinary converter through the aid of the signal location pointer.

REFERENCES:
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patent: 4802174 (1989-01-01), Hiraiwa et al.
patent: 4837766 (1989-06-01), Yoshida
IEEE Transactions on Communications, vol. com-31, No. 2, pp. 290-295, Feb. 983, P. J. McLane, "The Viterbi Receiver for Correlative Encoded MSK Signals".
"The Viterbi Receiver for Correlative Encoded MSK Signals", IEEE Transactions on Communications, vol. COM-31, No. 2, Feb. 1983, P. J. McLane.

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