Multiple quadrature-phase amplitude modulating system capable of

Details Multiple quadrature-phase amplitude modulating system capable of Multiple quadrature-phase amplitude modulating system capable of

1985-09-23

1987-06-23

Laroche, Eugene R.

Modulators

Amplitude modulator

Nonlinear device controlled by modulating signal

332 48, 375 41, H04L 2712

Patent

active

046756191

ABSTRACT:
In a multiple QAM system in which a pair of quadrature-phase carrier signals is modulated by a first and a second input digital signal, each representative of N or less levels, into a quadrature-phase amplitude modulated signal having M signal points on a phase plane where M is equal to N.sup.2, a code converting unit (41) converts the digital signals according to a predetermined rule into a first and a second modulating signal for use in modulating the carrier signals with the M signal points arranged approximately at a circle of a diameter which is shorter than a diagonal of a square of a side corresponding to the N levels. In a counterpart demodulating system, a pair of demodulated signals is derived from the amplitude modulated signal and converted into reproductions of the respective digital signals according to an inverse of the predetermined rule.

REFERENCES:
patent: 4077021 (1978-02-01), Csajka et al.
Tanaka et al., "Correlative QAM", Electronics and Communications in Japan, vol. 61-B, No. 2, 1978.

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