Patent US3740491A successfully refreshed from Google Patents.
US3740491A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital magnetic tape recoring system using symmetrical differential pulse width modulation with a triangular reference signal
Assignee: Individual
•
Filing: 1971-04-23
•
Granted: 1973-06-19
•
Expires: 1991-04-23
Abstract
Abstract The present invention relates to a recording system capable of providing either an analog or a digital output signal. The system includes: a symmetrical triangular wave generator; information signal sensing transducers; pulse width modulator means for producing a symmetrical output pulse signal; semi-permanent realtime recording means for recording the modulator output pulses; and output means for providing both an analog and digital output signal from the system.
Inventors
- 👤 G Cook
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:40
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/16
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
135 words
A symmetrical differential pulse width modulation system comprising: means for generating a periodic symmetrical triangular reference signal having equal plus and minus slopes respectively terminating in upper and lower points of uniform periodicity; sensing means for providing a modulating signal; reference signal modulating means, having as inputs thereto said triangular reference signal and said modulating signal for producing a pulse width modulated signal that is symmetrical about points of uniform periodicity corresponding to said reference signal points of uniform periodicity so that said modulated signal is substantially free of phase distortion with respect to the periodicity of the reference signal. @. The system of claim 1, wherein: said modulating means sums the reference signal with the modulating signal; and said modulating means output changes its state in response to a zero crossing of said sum.
Claim 2
Dependent Claim
43 words
The system of claim 2, including: a recorder and playback means connected to the output of said modulating means for recording said modulated signal and said reference signal and for playing back said reference signal and said modulated signal to information retrieval means.
Claim 3
Dependent Claim
121 words
The system of claim 3, wherein: said information retrieval means includes a phase-locked loop having an input and an output; said input is coupled to the reference signal playback output of said recording and playback means; said output is a train of monopolaric pulses having a frequency which is a multiple of said modulated signal frequency; a gate having a first input coupled to the modulating signal playback output of said recording and playback means and a second inpUt coupled to said train of monopolaric pulses; the output of said gate being said train of monopolaric pulses gated by the modulated signal, wherein each train of gated monopolaric pulses defines the period of its corresponding gated signal independently of recording speed.
Claim 4
Dependent Claim
58 words
The system of claim 4, wherein the information retrieval means further includes; a low pass filter connected to said modulated signal playback output of said recording and playback means; said filter having a cut-off frequency between the upper signal frequency and the reference signal frequency; said low pass filter output being the modulating signal input to said modulator.
Claim 5
Dependent Claim
28 words
The system of claim 5, wherein: said modulating means is a summing amplifier latched at its positive or negative saturation voltage level in response to said zero crossings.
References Cited (Backward Citations)
US2950352A
Cited
US2972128A
Cited
US3009025A
Cited
US3170125A
Cited
US3167720A
Cited
US3509549A
Cited
US3551851A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-18 | 1976-12-18 | 1977-06-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-18 | 1980-12-18 | 1981-06-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-18 | 1984-12-18 | 1985-06-19 | $7700.00 | Window Closed / Lapsed |