Patent US3985978A successfully refreshed from Google Patents.
US3985978A
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US
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Method and apparatus for control of FM beat distortion
Assignee: Individual
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Filing: 1974-05-09
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Granted: 1976-10-12
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Expires: 1994-05-09
Abstract
Abstract A method and apparatus is disclosed for reducing crossover modulation distortion generated at a sub-channel and for minimizing phase differences between 4-channel signals that are recorded on a recording medium in a multiple-frequency manner. More specifically, the present invention is directed to reducing or eliminating the beat distortion that is caused by crosstalk between a sub-channel signal and a main channel signal when the main channel signal is recorded according to RIAA-TYPE recording characteristics.
Inventors
- 👤 Duane H. Cooper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:17
CPC Classifications
H; H04; H04S; H04S3/00; H04S3/006; G; G11; G11B; G11B20/00; G11B20/00992
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
253 words
Apparatus for recording 4-channel signals as main channel and frequency modulated subchannel signals on two groove-walls of a recording disc with provision for reduction of crossover modulation distortion, comprising first main channel input means for a first main channel signal, second main channel input means for a second main channel signal, first subchannel input means for a first subchannel signal to be recorded on a first recording disc groovewall with said first main channel signal, second subchannel input means for a second subchannel signal to be recorded on a second recording disc groovewall with said second main channel signal, means for angularly modulating a carrier signal with said first and second subchannel signals, respectively, to provide a first angularly modulated subchannel signal and a second angularly modulated subchannel signal, recording equalizer means for emphasizing said first and said second main channel signals in accordance with the RIAA recording characteristic, means for providing said first and said second subchannel signals with an emphasis characteristic such that the modulation curve of said modulated subchannel signals corresponds to said RIAA emphasis characteristic of said recording equalizer means, means for adding said first angularly modulated signal and said first main channel signal to provide a recording signal for said first groovewall, means for adding said second angularly modulated subchannel signal and said second main channel signal to provide a recording signal for said second groovewall, and recording means for recording said first and second recording signals, respectively, on the first and second groovewalls of a recording disc.
Claim 2
Dependent Claim
253 words
Apparatus for recording 4-channel signals as main channel and frequency modulated subchannel signals on two groove-walls of a recording disc with provision for reduction of crossover modulation distortion, comprising first main channel input means for a first main channel signal, second main channel input means for a second main channel signal, first subchannel input means for a first subchannel signal to be recorded on a first recording disc groovewall with said first main channel signal, second subchannel input means for a second subchannel signal to be recorded on a second recording disc groovewall with said second main channel signal, means for angularly modulating a carrier signal with said first and second subchannel signals, respectively, to provide a first angularly modulated subchannel signal and a second angularly modulated subchannel signal, recording equalizer means for emphasizing said first and said second main channel signals in accordance with the RIAA recording characteristic, means for providing said first and said second subchannel signals with an emphasis characteristic such that the modulation curve of said modulated subchannel signals corresponds to said RIAA emphasis characteristic of said recording equalizer means, means for adding said first angularly modulated signal and said first main channel signal to provide a recording signal for said first groovewall, means for adding said second angularly modulated subchannel signal and said second main channel signal to provide a recording signal for said second groovewall, and recording means for recording said first and second recording signals, respectively, on the first and second groovewalls of a recording disc.
Claim 3
Dependent Claim
89 words
Apparatus in accordance with claim 1 wherein the value of the log of the modulation index of said modulation curve versus the log of the frequency of the subchannel signal of said modulation curve increases with decreasing frequency from a corner frequency of about 100 Hz or less, remains constant from said corner frequency to about 500 Hz, decreases with increasing frequency from about 500 Hz to about 2100 Hz, remains constant from about 2100 Hz to about 6000 Hz, and decreases with increasing frequency above about 6000 Hz.
Claim 4
Dependent Claim
31 words
Apparatus in accordance with claim 2 further including matrixing means for providing main channel signals TL and TR and subchannel signals TT and TQ in accordance with the UM matrixing system.
Claim 5
Dependent Claim
31 words
Apparatus in accordance with claim 3 further including means for reducing the lower frequency range of subchannnel signal TQ while maintaining its relative phase relationship with signals TL, TR and TT.
Claim 6
Dependent Claim
35 words
Apparatus in accordance with claim 3 further including means for matrixing signals TT and TQ to provide said first and second subchannel signals as TT + kTQ and TT-kTQ where k is less than 1/2.
Claim 7
Dependent Claim
10 words
Apparatus in accordance with claim 5 wherein k is 1/3.
Claim 8
Dependent Claim
71 words
A two channel recording with provision for reduction of crossover modulation distortion having 4-channel audio signals recorded thereon as two main channel and two frequency modulated subchannel signals wherein one main channel and one frequency modulated subchannel are recorded on each channel of the recording and wherein each of said recorded subchannel signals has a modulation index emphasis which corresponds to the recording emphasis of each of said main channel signals.
Claim 9
Dependent Claim
71 words
A two channel recording with provision for reduction of crossover modulation distortion having 4-channel audio signals recorded thereon as two main channel and two frequency modulated subchannel signals wherein one main channel and one frequency modulated subchannel are recorded on each channel of the recording and wherein each of said recorded subchannel signals has a modulation index emphasis which corresponds to the recording emphasis of each of said main channel signals.
Claim 10
Dependent Claim
28 words
A recording in accordance with claim 7 wherein the recording is a recording disc and wherein the emphasis characteristic of said main channel signals is the RIAA characteristic.
Claim 11
Dependent Claim
87 words
A recording disc in accordance with claim 8 wherein the value of the log of said modulation index versus the log of the frequency of the subchannel signal of said modulation curve increases with decreasing frequency from a corner frequency of about 100 Hz or less, remains constant from said corner frequency to about 500 Hz, decreases with increasing frequency from about 500 Hz to about 2100 Hz, remains constant from about 2100 Hz to about 6000 Hz, and decreases with increasing frequency above about 6000 Hz.
Claim 12
Dependent Claim
44 words
A recording disc in accordance with claim 9 wherein the main channel signals are TL and TR and wherein the subchannel signals are TT + kTQ and TT - kTQ where k is less than 1/2, matrixed in accordance with the UM matrixing system.
Claim 13
Independent Claim
135 words
A method for recording 4-channel signals as main channel and frequency modulated subchannel signals comprising providing first and second main channel signals having a recording emphasis characteristic, providing first and second subchannel signals, angularly modulating a carrier signal with said first and second subchannel signals to provide a first angularly modulated subchannel signal and a second angularly modulated subchannel signal having a modulation index emphasis characteristic corresponding to said main channel recording characteristic, adding said first angularly modulated signal and said first main channel signal to provide a recording signal for a first recording channel, adding said second angularly modulated subchannel signal and said second main channel signal to provide a recording signal for a second recording channel, and recording said first and second recording signals as the first and second channels of a recording.
Claim 14
Independent Claim
135 words
A method for recording 4-channel signals as main channel and frequency modulated subchannel signals comprising providing first and second main channel signals having a recording emphasis characteristic, providing first and second subchannel signals, angularly modulating a carrier signal with said first and second subchannel signals to provide a first angularly modulated subchannel signal and a second angularly modulated subchannel signal having a modulation index emphasis characteristic corresponding to said main channel recording characteristic, adding said first angularly modulated signal and said first main channel signal to provide a recording signal for a first recording channel, adding said second angularly modulated subchannel signal and said second main channel signal to provide a recording signal for a second recording channel, and recording said first and second recording signals as the first and second channels of a recording.
Claim 15
Dependent Claim
37 words
A method in accordance with claim 11 wherein said first and second channels are the first and second groovewalls of a recording disc and wherein said main channels are emphasized in accordance with the RIAA recording characteristic.
Claim 16
Dependent Claim
86 words
A method in accordance with claim 12 wherein the value of the log of said modulation index versus the log of the frequency of the subchannel signal of said modulation curve increases with decreasing frequency from a corner frequency of about 100 Hz or less, remains constant from said corner frequency to about 500 Hz, decreases with increasing frequency from about 500 Hz to about 2100 Hz, remains constant from about 2100 Hz to about 6000 Hz, and decreases with increasing frequency above about 6000 Hz.
Claim 17
Dependent Claim
42 words
A method in accordance with claim 12 further including the steps of providing main channel signals TL and TR and subchannel signals TT + kTQ and TT - kTQ where k is less than 1/2, in accordance with the UM matrixing system.
Claim 18
Dependent Claim
55 words
A method in accordance with claim 14 wherein the frequency spectra of signals TL and TR is from about 30 to about 18,000 Hz, wherein the frequency spectrum of signal TT is from about 30 to about 6000 Hz, and wherein the frequency spectrum of signal TQ is from about 130 to about 6000 Hz.
Claim 19
Dependent Claim
102 words
In an apparatus for reproducing 4-channel signals recorded as main channel and frequency modulated subchannel signals on 2 groovewalls of a recording disc having the main channel signals of the recording disc recorded thereon with an RIAA emphasis recording characteristic, said apparatus including a preamplifier for signals from a recording disc pickup device, and a reproducing equalizer for the main channel signals, the improvement comprising said apparatus including means for filtering and demodulating said modulated subchannel signals to provide demodulated subchannel signals and for emphasizing said demodulated subchannel signals with an emphasis characteristic which is the reverse of the RIAA recording characteristic.
Claim 20
Dependent Claim
102 words
In an apparatus for reproducing 4-channel signals recorded as main channel and frequency modulated subchannel signals on 2 groovewalls of a recording disc having the main channel signals of the recording disc recorded thereon with an RIAA emphasis recording characteristic, said apparatus including a preamplifier for signals from a recording disc pickup device, and a reproducing equalizer for the main channel signals, the improvement comprising said apparatus including means for filtering and demodulating said modulated subchannel signals to provide demodulated subchannel signals and for emphasizing said demodulated subchannel signals with an emphasis characteristic which is the reverse of the RIAA recording characteristic.
References Cited (Backward Citations)
US3786193A
Cited
US3761628A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-10-12 | 1980-04-12 | 1980-10-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-10-12 | 1984-04-12 | 1984-10-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-10-12 | 1988-04-12 | 1988-10-12 | $7700.00 | Window Closed / Lapsed |