US3674939A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Baseband pulse code modulation system
Assignee: Individual
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Filing: 1969-11-26
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Granted: 1972-07-04
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Expires: 1989-11-26
Abstract
Abstract Pulse code modulation system for reducing bandwidth in which voice signal input is compressed, limited, filtered into frequency channels, all of which are converted to the same baseband frequency and are fed to a time sharing multiplexing circuit followed by an analog to digital circuit for transmission. The digital signal is received, converted to analog, demultiplexed, demodulated to voice frequency channels and bandpass filtered. The number of channels applied to the time sharing circuit can be reduced by common band occupancy quadrature carrier methods and then converted to baseband.
Inventors
- 👤 Fred A Brooks
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 11:16
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/68
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
414 words
A pulse code modulation system comprising: a. a voice signal source; b. a sequence of first band pass filters parallel fed by the signal source; c. a sequence of baseband modulators fed one each by the sequence of band pass filters the baseband consisting of a frequency range starting with DC and having the same bandwidth as the first bandpass filters; d. a sequence of baseband oscillators connected to one each of the sequence of baseband modulators, the oscillators having a preselected frequency for producing a baseband; e. a first sequence of quadrature modulators fed by one each of the sequence of baseband modulators; f. a plurality of orthogonal oscillator circuits, each circuit including a series connected oscillator and a 90* phase shifter and connecting the first sequence of the quadrature modulators into a plurality of pairs with a first quadrature modulator of each pair being connected to a second quadrature modulator one half of the sequence from the first quadrature modulator of the pair; g. a sequence of second band pass filters fed by the outputs of the first sequence of quadrature modulators; h. a plurality of third modulators fed by one each of the plurality of second band pass filters; i. means for time sharing multiplexing fed by the plurality of third modulators; j. an analog to digital converter fed by the time sharing multiplexing means; k. means for transmitting the digital output signal of the analog to digital converter; l. means for receiving the transmitted output; m. a digital to analog converter fed by the receiving means; n. means for time sharing demultiplexing fed by the digital to analog converter; o. a plurality of fourth modulators fed by the time sharing demultiplexing means; p. a sequence of third band pass filters fed by one each of the plurality of fourth modulators; q. a second sequence of quadrature modulators fed by one each of the second plurality of band pass filters; r. a second plurality of orthogonal circuits, each circuit including a series connected oscillator and a 90* phase shifter and connecting the second sequence of quadrature modulators into a plurality of pairs with a first quadrature modulator of each pair being connected to a second quadrature modulator one half of the sequence from the first quadrature modulator of the pair; and s. means for converting the output of the second sequence of quadrature modulators to audio signals, the converting means including a sequence of audio modulators and a sequence of oscillators.
Claim 2
Dependent Claim
414 words
A pulse code modulation system comprising: a. a voice signal source; b. a sequence of first band pass filters parallel fed by the signal source; c. a sequence of baseband modulators fed one each by the sequence of band pass filters the baseband consisting of a frequency range starting with DC and having the same bandwidth as the first bandpass filters; d. a sequence of baseband oscillators connected to one each of the sequence of baseband modulators, the oscillators having a preselected frequency for producing a baseband; e. a first sequence of quadrature modulators fed by one each of the sequence of baseband modulators; f. a plurality of orthogonal oscillator circuits, each circuit including a series connected oscillator and a 90* phase shifter and connecting the first sequence of the quadrature modulators into a plurality of pairs with a first quadrature modulator of each pair being connected to a second quadrature modulator one half of the sequence from the first quadrature modulator of the pair; g. a sequence of second band pass filters fed by the outputs of the first sequence of quadrature modulators; h. a plurality of third modulators fed by one each of the plurality of second band pass filters; i. means for time sharing multiplexing fed by the plurality of third modulators; j. an analog to digital converter fed by the time sharing multiplexing means; k. means for transmitting the digital output signal of the analog to digital converter; l. means for receiving the transmitted output; m. a digital to analog converter fed by the receiving means; n. means for time sharing demultiplexing fed by the digital to analog converter; o. a plurality of fourth modulators fed by the time sharing demultiplexing means; p. a sequence of third band pass filters fed by one each of the plurality of fourth modulators; q. a second sequence of quadrature modulators fed by one each of the second plurality of band pass filters; r. a second plurality of orthogonal circuits, each circuit including a series connected oscillator and a 90* phase shifter and connecting the second sequence of quadrature modulators into a plurality of pairs with a first quadrature modulator of each pair being connected to a second quadrature modulator one half of the sequence from the first quadrature modulator of the pair; and s. means for converting the output of the second sequence of quadrature modulators to audio signals, the converting means including a sequence of audio modulators and a sequence of oscillators.
Claim 3
Dependent Claim
38 words
A pulse code modulation system according to claim 1 which further comprises: a. a voice compressor fed by the signal source; and b. a peak limiter interposed between the voice compressor and the sequence of band pass filters.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-04 | 1976-01-03 | 1976-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-04 | 1980-01-03 | 1980-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-04 | 1984-01-03 | 1984-07-04 | $7700.00 | Window Closed / Lapsed |