Method for generating modem transmission signals with quadrature

Details Method for generating modem transmission signals with quadrature Method for generating modem transmission signals with quadrature

1980-04-02

1982-04-27

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

375 39, 375 42, 375 53, 375 54, 332 17, H03K 710, H04L 512

Patent

active

043274390

ABSTRACT:
A method for generating modem transmission signals with quadrature amplitude modulation (QAM) wherein scanned values of elementary bandpass signals are stored in digitally coded form, the elementary bandpass signals are weighted with coefficients depending on the information to be transmitted and the modem transmission signals are formed by superposition of the thus weighted elementary bandpass signals; and wherein in the case of n-PSK modulation, where n=4, 8, 12, 16 . . . , the phase positions of all elementary bandpass signals are selected such that the phase diagram is symmetrical to the axis .phi.=0, and no elementary bandpass signal coincides with the axis .phi.=0; 1/4n elementary bandpass signals, which cannot be derived from any other bandpass signal of phase diagram neither due to symmetry with the axis .phi.=0 or the axis .phi.=90.degree., respectively, nor by symmetry to the origin of the diagram, are stored in a digital memory; and the remaining, e.g. 3/4n, elementary bandpass signals are obtained by weighting the stored elementary bandpass signals with +1 or -1, respectively, and/or reading out the memory in a forward or a backward direction, respectively.

REFERENCES:
patent: 3887768 (1975-06-01), Forney, Jr. et al.
patent: 3925611 (1975-12-01), Dennis
patent: 3955141 (1976-05-01), Lyon et al.
patent: 4247944 (1981-01-01), Sifford
patent: 4271527 (1981-06-01), Armstrong

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