Modulators – Amplitude modulator – Nonlinear device controlled by modulating signal
Patent
1988-06-20
1989-08-08
Grimm, Siegfried H.
Modulators
Amplitude modulator
Nonlinear device controlled by modulating signal
332 18, 375 39, H03C 500, H04L 2700
Patent
active
048556920
ABSTRACT:
A square array of signal points forming a QAM signal point constellation is modified by relocating signal points from corners of the square to positions extrapolated from the square array and at reduced distances from the origin, corresponding to reduced peak amplitude levels. The relocation is effected in a manner to maintain, at least for a majority of the relocated points, a Hamming distance of one. To this end for a constellation of 2.sup.2n points, with n=4 or more and points with I and Q amplitudes 1, 3, 5, . . . 2.sup.n -1 units in the square array, a plurality of points in each quadrant are relocated to positions, relative to positions which they would have in the square array, rotated through an angle of 180.degree. about predetermined reference points having I and Q amplitude co-ordinates of (2.sup.n,2.sup.n-1) and (2.sup.n-1,2.sup.n). Specific examples are described for 256 QAM (n=4) and 1024 QAM (n=5).
REFERENCES:
patent: 4675619 (1987-06-01), Uchibori et al.
patent: 4716385 (1987-12-01), Noda et al.
patent: 4750191 (1988-06-01), Yoshida
"A Stepped Square 256QAM for Digital Radio System", by T. Ryu et al., ICC'86, Jun. 1986, pp. 1477-1481.
"Digital Amplitude-Phase Keying with M-ary Alphabets" by Melvil C. Thomas et al., 1972, International Telemetry Conference, Los Angeles, California, IEEE Transactions on Communications, Feb. 1974, pp. 168-179.
"Odd-Bit Quadrature Amplitude-Shift Keying", Joel G. Smith, 1974 Telemetering Conference, Los Angeles, California, Oct. 15-17, published in IEEE Transactions on Communications, Mar. 1973.
"Duplex Transmission at 4800 and 9600 Bits/s on the General Switched Telephone Network and the Use of Channel Coding with a Partitioned Signal Constellation" by John D. Brownlie et al., Proceedings of the 1984 Zurich Seminar on Digital Communications, Mar. 6-8, 1984, pp. 113-120.
Kennard Paul A.
McNicol John D.
Middleton Joseph L.
Wu Kuang-Tsan
Grimm Siegfried H.
Haley R. John
Northern Telecom Limited
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