Patent US3902131A successfully refreshed from Google Patents.
US3902131A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tandem audio dynamic range expander
Assignee: Panasonic Corp of North America
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Filing: 1974-09-06
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Granted: 1975-08-26
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Expires: 1994-09-06
Abstract
Abstract An audio signal which has been compressed at two different frequencies for recording is expanded to its initial characteristics for reproduction by means of a tandem expander wherein the incoming signal is divided into paths representing a mid band variable gain path and a high band variable gain path and the two variable gain paths are subtracted from the main signal to provide a signal expanded in dynamic range. The control voltage for the high band variable gain path is extracted from the incoming signal. The system is particularly useful in the demodulation of discreet four-channel records.
Inventors
- 👤 Louis Dorren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:51
CPC Classifications
H; H03; H03G; H03G9/00; H03G9/02; H03G9/025
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
368 words
An audio expander for increasing the dynamic range of an audio signal, which has been compressed in amplitude at a high band frequency and at a mid band frequency, to restore the signal to its original dynamic range, comprising in combination: a. means for receiving an incoming audio signal and dividing said signal into three paths, b. passing a first path signal through a first inverting amplifier to produce an output signal having substantially the same amplitude as the incoming signal and inverted 180*, c. passing a second path signal through mid band frequency shaping means, said means having an output representing the unattenuated mid band frequency wherein higher and lower frequencies are attenuated, d. passing a portion of the output of said mid band means through a rectifier to obtain a DC control voltage, e. passing another portion of the output of said mid band means through a first variable gain amplifier wherein the variable gain of said amplifier is determined by said DC control voltage, the gain of said amplifier being inversely proportional to the control voltage, f. combining the output of said first variable gain amplifier with said inverted output of first inverting amplifier whereby the outputs of the two amplifiers subtract, g. passing the thus produced combined signal to a second inverting amplifier wherein said amplifier has an output 180* out of phase with its input and in phase with the initial signal, h. passing a third path input signal through a high band frequency shaping means and a rectifier to derive a second control voltage, i. passing a portion of the signal representing the output of the first inverting amplifier and the first variable gain amplifier to a second high band frequency shaping means, said means having an output representing the unattenuated high band frequency wherein higher and lower frequencies are attenuated, j. passing said output from said second high band frequency shaping means to the input of a second variable gain amplifier, k. passing said second control voltage to said second variable gain amplifier, and l. adding the output of the second inverting amplifier to the output of the second variable gain amplifier to derive an audio signal exxpanded in dynamic range.
Claim 2
Dependent Claim
368 words
An audio expander for increasing the dynamic range of an audio signal, which has been compressed in amplitude at a high band frequency and at a mid band frequency, to restore the signal to its original dynamic range, comprising in combination: a. means for receiving an incoming audio signal and dividing said signal into three paths, b. passing a first path signal through a first inverting amplifier to produce an output signal having substantially the same amplitude as the incoming signal and inverted 180*, c. passing a second path signal through mid band frequency shaping means, said means having an output representing the unattenuated mid band frequency wherein higher and lower frequencies are attenuated, d. passing a portion of the output of said mid band means through a rectifier to obtain a DC control voltage, e. passing another portion of the output of said mid band means through a first variable gain amplifier wherein the variable gain of said amplifier is determined by said DC control voltage, the gain of said amplifier being inversely proportional to the control voltage, f. combining the output of said first variable gain amplifier with said inverted output of first inverting amplifier whereby the outputs of the two amplifiers subtract, g. passing the thus produced combined signal to a second inverting amplifier wherein said amplifier has an output 180* out of phase with its input and in phase with the initial signal, h. passing a third path input signal through a high band frequency shaping means and a rectifier to derive a second control voltage, i. passing a portion of the signal representing the output of the first inverting amplifier and the first variable gain amplifier to a second high band frequency shaping means, said means having an output representing the unattenuated high band frequency wherein higher and lower frequencies are attenuated, j. passing said output from said second high band frequency shaping means to the input of a second variable gain amplifier, k. passing said second control voltage to said second variable gain amplifier, and l. adding the output of the second inverting amplifier to the output of the second variable gain amplifier to derive an audio signal exxpanded in dynamic range.
Claim 3
Dependent Claim
28 words
The structure of claim 1 wherein the mid band frequency shaping means is centered at 630 Hz and the high band shaping means is centered on 15 kHz.
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) | 1978-08-25 | 1979-02-24 | 1979-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-25 | 1983-02-24 | 1983-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-25 | 1987-02-24 | 1987-08-26 | $7700.00 | Window Closed / Lapsed |