Patent US4435682A successfully refreshed from Google Patents.
US4435682A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency demodulator employing a circuit having a delay varying with the received frequency
Assignee: US Philips Corp
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Filing: 1981-06-23
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Granted: 1984-03-06
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Expires: 2001-06-23
Abstract
Abstract A frequency demodulator including an "exclusive-OR" circuit receiving two square-wave signals having a frequency corresponding to a frequency-modulated signal, and a delay circuit for delaying one of the square-wave signals before application to the "exclusive-OR" circuit, by a delay varying versus frequency in such a way that the absolute value of the phase difference between the square-wave signals varies at most from 0° to 180° inversely with respect to changes in frequency. The output signal of the demodulator is supplied by a low-pass filter connected to the output of the "exclusive-OR" circuit.
Inventors
- 👤 Robert Boudault
- 👤 Gerard Pouzoullic
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 09:39
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/18; H03D3/20; H03K; H03K9/00; H03K9/06; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/156; H04L27/1563; H03D2200/00; H03D2200/0001; H03D2200/0039; H03D2200/0041; H03D2200/0094; H03D2200/0096
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
144 words
A frequency demodulator comprising a first gate circuit having an "exclusive-OR" function and receiving at its two inputs square-wave signals each having a frequency corresponding to a frequency modulated signal, delay means for delaying one of said square-wave signals relative to the other before application to said first gate circuit, and a low-pass filter connected to the output of the first gate circuit, said delay means producing a delay varying with frequency in an inversely proportional sense such that the phase difference between said square-wave signals varies at most from 0° to 180°, characterized in that said delay means comprises an integrating circuit receiving the non-delayed signal and producing an output signal, and a comparator for comparing said output signal of the integrating circuit with a threshold signal and producing a comparator output signal, the delayed signal being derived from said comparator output signal.
Claim 2
Dependent Claim
144 words
A frequency demodulator comprising a first gate circuit having an "exclusive-OR" function and receiving at its two inputs square-wave signals each having a frequency corresponding to a frequency modulated signal, delay means for delaying one of said square-wave signals relative to the other before application to said first gate circuit, and a low-pass filter connected to the output of the first gate circuit, said delay means producing a delay varying with frequency in an inversely proportional sense such that the phase difference between said square-wave signals varies at most from 0° to 180°, characterized in that said delay means comprises an integrating circuit receiving the non-delayed signal and producing an output signal, and a comparator for comparing said output signal of the integrating circuit with a threshold signal and producing a comparator output signal, the delayed signal being derived from said comparator output signal.
Claim 3
Dependent Claim
75 words
A frequency demodulator as claimed in claim 1, characterized in that said output signal of the integrating circuit is obtained at one terminal of a capacitor of said integrating circuit, the other terminal of said capacitor receiving a signal derived from the non-delayed signal and the output signal of said first gate circuit having an "exclusive-OR" function, said threshold signal being a one-level signal and the delayed signal being constituted by said comparator output signal.
Claim 4
Dependent Claim
61 words
A frequency demodulator as claimed in claim 2, characterized in that said signal applied to said other terminal of said capacitor is formed at the output of a second "exclusive-OR" gate circuit, said second "exclusive-OR" gate circuit receiving at one input the output signal of said first gate circuit and at its other input a complementary signal of the non-delayed signal.
Claim 5
Dependent Claim
96 words
A frequency demodulator as claimed in claim 1, characterized in that said output signal of the integrating circuit is obtained at one terminal of a capacitor of said integrating circuit, said one terminal receiving the delayed signal through a first resistor and the non-delayed signal through a second resistor constituting the resistor of said integrating circuit, the other terminal of said capacitor being at fixed potential, said threshold signal being a two-level signal obtained by means of a voltage divider receiving the delayed signal, and the delayed signal being constituted by the inverted comparator output signal.
Claim 6
Dependent Claim
56 words
A frequency demodulator as claimed in claim 4, characterized in that the components of the circuits serving to form the delayed signal are adjusted in such a way that the phase difference between the said delayed and non-delayed square-wave signals is substantially zero for the highest frequency and substantially equal to 180° for the lowest frequency.
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) | 1987-03-06 | 1987-09-05 | 1988-03-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-06 | 1991-09-05 | 1992-03-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-06 | 1995-09-05 | 1996-03-06 | $7700.00 | Window Closed / Lapsed |