US4371747A
Expired / Lapsed
US
⏱️ 0.0 years remaining
AM Stereophonic decoder
Assignee: Motorola Solutions Inc
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Filing: 1980-03-24
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Granted: 1983-02-01
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Expires: 2000-03-24
Abstract
Abstract A decoder for use with a compatible AM stereophonic signal utilizes a amplifier and a feedback loop from the amplifier output to control the output of a multiplier circuit which is one input to the amplifier. The amplifier output is thus forced to become the required correction factor used in restoring the stereo program signals.
Inventors
- 👤 Francis H. Hilbert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:07
CPC Classifications
H; H04; H04H; H04H20/00; H04H20/44; H04H20/46; H04H20/47; H04H20/49; H10; H10F; H10F30/00; H10F30/20; H10F30/21; H10F30/28; H10F30/283; H10F30/2843
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
152 words
A receiver for receiving AM stereophonic signals of the form (1+L+R)cos(ω c t+φ) where L and R are information signals, ω c t is a carrier frequency, and φ is arc tan {(L-R)/)1+L+R)}, and comprising: means for selectively receiving said stereophonic signals; means coupled to the selective receiving means for detecting the amplitude modulation on the received signal; means for providing two carrier signals in quadrature; multiplier means coupled to the selective receiving means and to the carrier signal means; amplifier means coupled to the amplitude detection means and the multiplier means for providing a correcting signal proportional to the inverse of cosine φ, said correcting signal being coupled back to the multiplier means for providing a pair of multiplier output signals which are substantially equal to 1+L+R and L-R; and matrixing means coupled to receive the signals (1+L+R) and (L-R) and to provide output signals substantially equal to L and R.
Claim 2
Dependent Claim
152 words
A receiver for receiving AM stereophonic signals of the form (1+L+R)cos(ω c t+φ) where L and R are information signals, ω c t is a carrier frequency, and φ is arc tan {(L-R)/)1+L+R)}, and comprising: means for selectively receiving said stereophonic signals; means coupled to the selective receiving means for detecting the amplitude modulation on the received signal; means for providing two carrier signals in quadrature; multiplier means coupled to the selective receiving means and to the carrier signal means; amplifier means coupled to the amplitude detection means and the multiplier means for providing a correcting signal proportional to the inverse of cosine φ, said correcting signal being coupled back to the multiplier means for providing a pair of multiplier output signals which are substantially equal to 1+L+R and L-R; and matrixing means coupled to receive the signals (1+L+R) and (L-R) and to provide output signals substantially equal to L and R.
Claim 3
Dependent Claim
100 words
A receiver in accordance with claim 1 wherein the multiplier means comprises a first multiplier coupled to multiply a signal from the selective receiving means and a first signal from the carrier signal providing means, a second multiplier coupled to multiply the signal from the selective receiving means and a second signal from the carrier signal providing means, a third multiplier coupled to multiply the output signal of the first multiplier and the output signal of the amplifier means, a fourth multiplier coupled to multiply the output signal from the second multiplier and the output signal from the amplifier means.
Claim 4
Dependent Claim
74 words
A receiver in accordance with claim 1 wherein the multiplier means comprises a first multiplier coupled to multiply a signal from the selective receiving means and a signal from the amplifier means, a second multiplier coupled to multiply a signal from the first multiplier and a signal from the carrier providing means, and a third multiplier coupled to multiply the signal from the first multiplier and a second signal from the carrier providing means.
Claim 5
Dependent Claim
44 words
A receiver in accordance with claim 3 wherein the first multiplier means comprises two diodes coupled across a current proportional to the output of the selective receiving means, and the amplifier means output provides a proportional current source to the junction of the diodes.
Claim 6
Dependent Claim
22 words
A receiver in accordance with claim 1 wherein the carrier providing means comprises an oscillator means and a 90° phase shifting means.
Claim 7
Dependent Claim
19 words
A receiver in accordance with claim 1 wherein the carrier providing means includes an oscillator and two divider means.
Claim 8
Dependent Claim
20 words
A receiver in accordance with claim 1 wherein the selective receiving means comprises an RF stage and an IF stage.
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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) | 1986-01-31 | 1986-08-02 | 1987-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-01-31 | 1990-08-02 | 1991-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-01-31 | 1994-08-02 | 1995-02-01 | $7700.00 | Window Closed / Lapsed |