Method and apparatus for bandwidth reduction

Details Method and apparatus for bandwidth reduction Method and apparatus for bandwidth reduction

1978-01-09

1981-03-10

Atkinson, Charles E.

Multiplex communications

Wide area network

Packet switching

370118, 333 17R, H04B 166

Patent

active

042556201

ABSTRACT:
The bandwidth of human speech signals, 125 to 3000 Hz, is reduced to approximately 125 to 1500 Hz by folding or shifting the high-frequency consonant-band portion, 1000 to 3000 Hz, into the low-frequency vowel-band portion, 125 to 1000 Hz. After transmission, the reduced speech signal is expanded to reconstruct an approximation of the original speech signal. One embodiment features folding (modulator carrier frequency is 3000 Hz) and modulator feedthrough. Another embodiment features shifting (carrier is 1800 Hz) and no modulator feedthrough. Both embodiments boost lower vowel frequencies prior to modulation, and use no switching circuitry.

REFERENCES:
patent: 1836824 (1931-12-01), Steinberg
patent: 1841142 (1931-01-01), Mathes
patent: 1948973 (1934-02-01), Steinberg
patent: 3069506 (1962-12-01), Hopner et al.
patent: 3914554 (1975-10-01), Seidel

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