US3878470A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fm demodulator
Assignee: RCA Corp
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Filing: 1973-07-16
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Granted: 1975-04-15
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Expires: 1993-07-16
Abstract
Abstract A source of frequency modulated signals is coupled to a coincidence detector by a first and a second signal path. The first and second signal paths have unequal signal delay characteristics so that the coincidence detector provides an output signal comprised of a series of substantially constant width pulses wherein pulse width is determined by the difference in signal delay between the first and second signal paths. A low pass filter is coupled to the coincidence detector for recovering the signal modulation represented by the series of substantially constant width pulses.
Inventors
- 👤 Jr Charles D Boltz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:40
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/18; H03D3/20; H03D3/04
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
320 words
Apparatus for demodulating a frequency modulated signal comprising: a source of frequency modulated signals having first and second signal output terminals providing first and second signals of opposite phase, a first signal processing channel comprising: a first coincidence detector; a first signal path coupled from said first signal terminal to said first coincidence detector; a second signal path coupled from said first signal terminal to said first coincidence detector; said first and second signal paths exhibiting unequal signal time delay characteristics whereby said first coincidence detector provides a first output signal which is a series of substantially constant width pulses having a width determined by the difference in signal delay between said first and second signal paths; and a second signal processing channel comprising: a second coincidence detector; a third signal path coupled from said second signal terminal to said second coincidence detector; a fourth signal path coupled from said second signal terminal to said second coincidence detector; said third and fourth signal paths exhibiting unequal signal time delay characteristics whereby said second coincidence detector provides a second output signal which is a series of substantially constant width pulses having a width determined by the difference in signal delay between said third and fourth signal paths, and occurring in timed relation with respect to pulses of said first output signal according to the relative phases of said first and second signals provided by said source of signals; summing means coupled to said first and second coincidence detectors and responsive to their respective output signals to provide a third output signal consisting of a series of substantially constant width pulses, the repetition rate of which is a multiple of said frequency modulated signal repetition rate; and low pass filter means coupled to said summing means and responsive to said third output for recovering the signal modulation represented by the summation of said first and second series of substantially constant width pulses.
Claim 2
Dependent Claim
320 words
Apparatus for demodulating a frequency modulated signal comprising: a source of frequency modulated signals having first and second signal output terminals providing first and second signals of opposite phase, a first signal processing channel comprising: a first coincidence detector; a first signal path coupled from said first signal terminal to said first coincidence detector; a second signal path coupled from said first signal terminal to said first coincidence detector; said first and second signal paths exhibiting unequal signal time delay characteristics whereby said first coincidence detector provides a first output signal which is a series of substantially constant width pulses having a width determined by the difference in signal delay between said first and second signal paths; and a second signal processing channel comprising: a second coincidence detector; a third signal path coupled from said second signal terminal to said second coincidence detector; a fourth signal path coupled from said second signal terminal to said second coincidence detector; said third and fourth signal paths exhibiting unequal signal time delay characteristics whereby said second coincidence detector provides a second output signal which is a series of substantially constant width pulses having a width determined by the difference in signal delay between said third and fourth signal paths, and occurring in timed relation with respect to pulses of said first output signal according to the relative phases of said first and second signals provided by said source of signals; summing means coupled to said first and second coincidence detectors and responsive to their respective output signals to provide a third output signal consisting of a series of substantially constant width pulses, the repetition rate of which is a multiple of said frequency modulated signal repetition rate; and low pass filter means coupled to said summing means and responsive to said third output for recovering the signal modulation represented by the summation of said first and second series of substantially constant width pulses.
Claim 3
Dependent Claim
51 words
Apparatus in accordance with claim 1 for demodulating a frequency modulated signal wherein: said source of frequency modulated signals comprises a limiter coupled to a phase splitter to provide squared signals of opposite phase in which respective positive and negative going transitions correspond to the zero crossings of the modulated signal.
Claim 4
Dependent Claim
304 words
Apparatus for demodulating a frequency modulated signal comprising: a source of frequency modulated signals; a limiter circuit coupled to said source to provide squared signals of substantially constant amplitude and width corresponding in time occurrence to zero axis crossings of said frequency modulated signal; a phase splitter coupled to said limiter output to provide first and second signals of opposite phase; a first signal channel having a first coincidence detector with one input direct coupled through a first signal path to said first phase splitter signal; said first coincidence detector having a second input coupled through a second signal path having first signal delay means; a second signal channel having a second coincidence detector with one input direct coupled through a third signal path to said second phase splitter signal, said second coincidence detector having a second input coupled through a fourth signal path having second signal delay means; said first and second signal delay means comprising first, second, and third devices for providing a predetermined signal delay so that the output of said first and second coincidence detectors comprises a series of pulses of substantially constant width and substantially constant amplitude, wherein said width is determined by the signal delay of said devices in said second and fourth signal paths as compared to the respective first and third direct coupled signal paths; summing means coupled to the output of said first and second coincidence detectors and responsive to the respective outputs to provide a third output consisting of a series of substantially constant amplitude and constant width pulses having a repetition rate which is a multiple of the repetition rate of said frequency modulated signals; and low pass filter means coupled to said third output for recovering the signal modulation represented by the summation of said first and second series of output pulses.
Claim 5
Dependent Claim
304 words
Apparatus for demodulating a frequency modulated signal comprising: a source of frequency modulated signals; a limiter circuit coupled to said source to provide squared signals of substantially constant amplitude and width corresponding in time occurrence to zero axis crossings of said frequency modulated signal; a phase splitter coupled to said limiter output to provide first and second signals of opposite phase; a first signal channel having a first coincidence detector with one input direct coupled through a first signal path to said first phase splitter signal; said first coincidence detector having a second input coupled through a second signal path having first signal delay means; a second signal channel having a second coincidence detector with one input direct coupled through a third signal path to said second phase splitter signal, said second coincidence detector having a second input coupled through a fourth signal path having second signal delay means; said first and second signal delay means comprising first, second, and third devices for providing a predetermined signal delay so that the output of said first and second coincidence detectors comprises a series of pulses of substantially constant width and substantially constant amplitude, wherein said width is determined by the signal delay of said devices in said second and fourth signal paths as compared to the respective first and third direct coupled signal paths; summing means coupled to the output of said first and second coincidence detectors and responsive to the respective outputs to provide a third output consisting of a series of substantially constant amplitude and constant width pulses having a repetition rate which is a multiple of the repetition rate of said frequency modulated signals; and low pass filter means coupled to said third output for recovering the signal modulation represented by the summation of said first and second series of output pulses.
Claim 6
Dependent Claim
73 words
Apparatus in accordance with claim 1 for demodulating a frequency modulated signal wherein: said first and third signal paths comprise a direct coupling to said first and second coincidence detectors; and said second and fourth signal paths include signal delay means such that the width of individual ones of said output pulses from said coincidence detectors is substantially equal to the delay characteristics of said delay means coupled to said second signal path.
Claim 7
Dependent Claim
53 words
Apparatus in accordance with claim 1 for demodulating a frequency modulated signal wherein: said signal delay means comprises at least one signal translating device exhibiting a predetermined delay in response to positive-going and negative-going transitions of said squared signal wave, said predetermined delay determining the width of said pulses of said output signal.
Claim 8
Dependent Claim
43 words
Apparatus in accordance with claim 1 wherein: said delay means comprises a plurality of signal amplifying stages, each said stage exhibiting a delay whereby the width of said output pulses is determined by the sum of the signal delays of said amplifying stage.
Claim 9
Dependent Claim
21 words
Apparatus in accordance with claim 1 wherein: said amplifying stages are similarly constructed and are operating in a common thermal environment.
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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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |