US3789143A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compander with control signal logarithmically related to the instantaneous rms value of the input signal
Assignee: MILLS-RALSTON Inc
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Filing: 1971-03-29
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Granted: 1974-01-29
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Expires: 1991-03-29
Abstract
Abstract A compander system for audio signal processing, in which two 90* phase separated signals are generated from an input audio signal. Each phase separated signal is processed through a converter which provides an output signal logarithmically related to the instantaneous rms value of the corresponding phase separated signal. The output currents from both converters are proportional to the square of the input currents, hence are summed to yield a virtually ripple free output. This summed output is then scaled and applied to control the gain of a variable gain amplifier which either compresses or expands the original input audio signal according to the gain of the latter amplifier. Thus, the expansion or compression is a continuous linear process proportioned to the rms value of the input audio signal.
Inventors
- 👤 D Blackmer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 00:31
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/62; H04B1/64; H03; H03G; H03G1/00; H03G1/0005; H03G7/00; H03G7/06
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
55 words
A compression and expanSion system for an input signal, comprising in combination means for sensing the amplitude of said input signal and for providing a variable DC control signal logarithmically related to the rms amplitude of said input signal, and means for amplifying said input signal by a gain variable responsively to said control signal.
Claim 2
Dependent Claim
55 words
A compression and expanSion system for an input signal, comprising in combination means for sensing the amplitude of said input signal and for providing a variable DC control signal logarithmically related to the rms amplitude of said input signal, and means for amplifying said input signal by a gain variable responsively to said control signal.
Claim 3
Dependent Claim
36 words
A system as defined in claim 1 wherein said means for amplifying is such that, expressing the levels of said input and output signals in decibels, said output signal is linearly related to said input signal.
Claim 4
Dependent Claim
26 words
A system as defined in claim 1 wherein said control signal is related to the logarithm of the short term rms value of said input signal.
Claim 5
Dependent Claim
90 words
A system as defined in claim 1 wherein said input signal has a time-varying amplitude and said means for sensing comprises a circuit for generating responsively to said input signal, a pair of second signals identical to one another except for a substantially constant 90* phase difference, a pair of means responsive to each of said second signals for generating corresponding third signals which are proportional to substantially the respective squares of the difference between instantaneous and average values of said seconds signals, and means for summing said third signals.
Claim 6
Dependent Claim
13 words
A system as defined in claim 4 wherein said third signals are currents.
Claim 7
Dependent Claim
61 words
A system as defined in claim 5 including a constant current source, and charge storage means so connected to said source and to said means for summing said third signals that the voltage of said charge storage means tends to change so as to bring the constant current from said source into substantial equality with the sum of said third signals.
Claim 8
Dependent Claim
91 words
A system as defined in claim 4 wherein each of said means for generating third signals comprises means for generating from said input signal Ei an output signal in the form log Ei for any polarity of Ei, means for amplifying the signal in the form log Ei by the factors +2 and -2 on separate channels, and means for half-wave rectifying the signal on each of said channels so as to obtain substantially the antilogs thereof in the form of currents having instantaneous values related to the square of Ei.
Claim 9
Dependent Claim
88 words
A system as defined in claim 7 including means for summing the half-wave rectified currents from each of said channels to provide one of said third signals, a constant current source, and charged storage means so connected to said source and to said means for summing said third signals that the voltage of said charge storage means tends to change so as to bring the long-term average sum of said third signals into substantial equality with the constant current from said source, said voltage being said control signal.
Claim 10
Dependent Claim
55 words
A system as defined in claim 1 wherein said means for amplifying said input signal varies said gain in proportion to the product of said control signal and a substantially constant gain factor which is respectively negative or positive according as the system is intended to compress or expand the amplitude of the input signal.
Claim 11
Dependent Claim
69 words
Method of conditioning an input signal comprising the steps of sensing said input signal and generating responsively thereto a variable DC control signal logarithmically related to the short-term rms value of said input signal, amplifying said input signal by a gain proportional to the product of said control signal times a substantially constant, selected gain factor which is negative to obtain signal compression or positive to obtain signal expansion.
Claim 12
Dependent Claim
69 words
Method of conditioning an input signal comprising the steps of sensing said input signal and generating responsively thereto a variable DC control signal logarithmically related to the short-term rms value of said input signal, amplifying said input signal by a gain proportional to the product of said control signal times a substantially constant, selected gain factor which is negative to obtain signal compression or positive to obtain signal expansion.
Claim 13
Dependent Claim
22 words
Method of conditioning an input signal as defined in claim 10 wherein said compression and expansion are substantially complementary in time response.
Claim 14
Dependent Claim
61 words
A compression and expansion system for a plurality of parallel input signals, comprising in combination means for summing all of said input signals; means for providing a control signal related tO the logarithm of the amplitude of the rms summed signals; means for amplifying each of said input signals by a gain variable responsively to the antilogarithm of said control signal.
Claim 15
Dependent Claim
61 words
A compression and expansion system for a plurality of parallel input signals, comprising in combination means for summing all of said input signals; means for providing a control signal related tO the logarithm of the amplitude of the rms summed signals; means for amplifying each of said input signals by a gain variable responsively to the antilogarithm of said control signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-28 | 1977-07-30 | 1978-01-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-28 | 1981-07-30 | 1982-01-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-28 | 1985-07-30 | 1986-01-29 | $7700.00 | Window Closed / Lapsed |