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US3899754A
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Delta modulation and demodulation with syllabic companding
Assignee: AT&T Inc
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Filing: 1974-05-09
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Granted: 1975-08-12
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Expires: 1994-05-09
Abstract
Abstract A delta modulator and demodulator are shown using double integration in the audio feedback loop and including a separate feedback loop for direct current offset compensation. The output bit pattern is analyzed to detect when an increase in companding stepsize is required. When required, a companding control voltage is generated and integrated at a syllabic rate. This syllabic integrator has a decay circuit providing a decay time approximately three times the attack time, thus insuring good voice tracking, acceptable noise trailoff, and at the same time causing exponential decay of digital errors at a syllabic rate. The companding control voltage is applied to a nonlinear current step generator simulating a logarithmic characteristic by piecewise linear current segments. Temperature-compensated transistor circuits are used in the step generator. Impedance isolation, combined with staged temperature compensation, provides stable and reproducible nonlinear current characteristics with standard integrated circuits.
Inventors
- 👤 Stephen Joseph Brolin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:34
CPC Classifications
H; H03; H03M; H03M3/00; H03M3/02; H03M3/022; H03M3/024
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
95 words
A delta modulator comprising a comparator, a source of input signals to one input of said comparator, a source of feedback signals around said comparator to the other input of said comparator, a pulse generator for generating an output pulse when said input signal exceeds said feedback signal as determined by said comparator, and a feedback circuit utilizing said output pulses to generate said feedback signals, characterized in that said feedback circuit includes a syllabic rate integrator having a charging time-constant proportional to syllabic attack times and a discharging time-constant proportional to syllabic decay times.
Claim 2
Dependent Claim
95 words
A delta modulator comprising a comparator, a source of input signals to one input of said comparator, a source of feedback signals around said comparator to the other input of said comparator, a pulse generator for generating an output pulse when said input signal exceeds said feedback signal as determined by said comparator, and a feedback circuit utilizing said output pulses to generate said feedback signals, characterized in that said feedback circuit includes a syllabic rate integrator having a charging time-constant proportional to syllabic attack times and a discharging time-constant proportional to syllabic decay times.
Claim 3
Dependent Claim
65 words
The delta modulator according to claim 1 further characterized in that said feedback circuit also includes a non-linear current generator comprising a plurality of transistors coupled to said integrator each operating in its linear range of amplification and connected to a common current output lead, and resistive biasing means for biasing each of said transistors so as to initiate operation at a different voltage threshold.
Claim 4
Dependent Claim
12 words
generating an output pulse when said input signal exceeds said feedback signal,
Claim 5
Dependent Claim
12 words
generating an output pulse when said input signal exceeds said feedback signal,
Claim 6
Dependent Claim
9 words
generating said feedback signals from said output pulses, and
Claim 7
Dependent Claim
9 words
generating said feedback signals from said output pulses, and
Claim 8
Dependent Claim
20 words
The delta modulator according to claim 2 wherein the voltage on said syllabic rate integrator controls aid nonlinear current generator.
Claim 9
Dependent Claim
26 words
The delta modulator according to claim 2 further characterized in that a similar semiconductor junction is connected in parallel with the base-emitter paths of said transistors.
Claim 10
Dependent Claim
13 words
decaying said feedback signal at a syllabic rate independent of said output pulses.
Claim 11
Dependent Claim
13 words
decaying said feedback signal at a syllabic rate independent of said output pulses.
Claim 12
Dependent Claim
16 words
generating nonlinear current pulses as said feedback signals with a plurality of linear semiconductor amplifiers, and
Claim 13
Dependent Claim
16 words
generating nonlinear current pulses as said feedback signals with a plurality of linear semiconductor amplifiers, and
Claim 14
Dependent Claim
51 words
The delta modulator according to claim 4 further characterized in that at least one of said transistors is driven by the emitter signal on another one of said transistors, and two similar semiconductor junctions are connected in parallel with the base-emitter paths of said one transistor and said another one transistor.
Claim 15
Dependent Claim
45 words
A delta encoder comprising a digitally-controlled feedback circuit, and a syllabic rate integrator in said feedback circuit having different charging and discharging time constants, said charging time constant being proportional to syllabic attack time and said discharging time constant being proportional to syllabic decay time.
Claim 16
Dependent Claim
45 words
A delta encoder comprising a digitally-controlled feedback circuit, and a syllabic rate integrator in said feedback circuit having different charging and discharging time constants, said charging time constant being proportional to syllabic attack time and said discharging time constant being proportional to syllabic decay time.
Claim 17
Dependent Claim
29 words
The delta encoder according to claim 6 wherein said discharging time constant is proportional to syllabic decay rates and is independent of the digital control of said feedback circuit.
Claim 18
Dependent Claim
38 words
A delta encoder comprising a nonlinear companding feedback path, a plurality of piecewise-linear semiconductor amplifiers contributing to an overall nonlinear feedback current, and resistive biasing means establishing a different threshold of response for each of said semiconductor amplifiers.
Claim 19
Dependent Claim
38 words
A delta encoder comprising a nonlinear companding feedback path, a plurality of piecewise-linear semiconductor amplifiers contributing to an overall nonlinear feedback current, and resistive biasing means establishing a different threshold of response for each of said semiconductor amplifiers.
Claim 20
Dependent Claim
23 words
The delta encoder according to claim 8 wherein said semiconductor amplifiers are temperature-compensated by similar semiconductor junctions in the amplifier control signal path.
Claim 21
Dependent Claim
24 words
The delta encoder according to claim 9 wherein said semiconductor amplifiers and said similar semiconductor junctions are fabricated on ths same integrated circuit chip.
Claim 22
Dependent Claim
20 words
The delta encoder according to claim 10 wherein said resistive biasing means comprise resistors external to said integrated circuit chip.
Claim 23
Independent Claim
12 words
The method of delta encoding analog input signals comprising the steps of
Claim 24
Independent Claim
12 words
The method of delta encoding analog input signals comprising the steps of
Claim 25
Dependent Claim
14 words
The method of delta encoding according to claim 12 further comprising the steps of
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-11 | 1979-02-10 | 1979-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-11 | 1983-02-10 | 1983-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-11 | 1987-02-10 | 1987-08-12 | $7700.00 | Window Closed / Lapsed |