US3794757A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fm pulse discriminator for duplex fm system
Assignee: International Standard Electric Corp
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Filing: 1972-06-07
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Granted: 1974-02-26
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Expires: 1992-06-07
Abstract
Abstract There is disclosed an FM discriminator for pulse signals transmitted by means of FM in the voice range where the carrier frequency and the modulating frequency are very close in frequency to each other. The discriminator includes a monostable multivibrator triggered by sine waves which are frequency modulated by a pulse signal. The modulating signal is recovered from the output pulses of the multivibrator by integration. The carrier frequency and modulating frequency are separated from each other by frequency doubling. This is accomplished by triggering the multivibrator by control signals derived from both half-cycles of each oscillation of the frequency modulated sine waves.
Inventors
- 👤 F Knabe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 14:08
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/156; H04L27/1563; H03; H03D; H03D3/00; H03D3/02; H03D3/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
271 words
A bidirectional two-wire data transmission system employing frequency modulation comprising: a first frequency modulation discriminator disposed in one direction of transmission of said transmission system; and a second frequency modulation discriminator disposed in the other direction of transmission of said transmission system; said one direction of transmission having a lower carrier frequency than said carrier frequency of said other direction of transmission; said first discriminator including a first input for first sine wave frequency modulated by a first pulse modulating signal, first means coupled to said first input to produce two control signals derived from both half-cycles of each oscillation of said first frequency modulated sine waves, a first monostable multivibrator coupled to said first means responsive to said two control signals to produce first output pulses for both half-cycles of each oscillation of said first frequency modulated sine waves, and second means coupled to said first multivibrator to integrate said first output pulses to recover said first modulating signal; and said second discriminator including a second input for second sine waves frequency modulated by a second pulse modulating signal, a third means coupled to said second input to produce a third control signal derived from a selected one of the two halfcycles of each oscillation of said second frequency modulated sine waves, a second monostable multivibrator coupled to said third means responsive to said third control signal to produce second output pulses for said selected one of the two half-cycles of each oscillation of said second frequency modulated sine waves, and fourth means coupled to said second multivibrator to integrate said second output pulses to recover said second modulating signal.
Claim 2
Dependent Claim
271 words
A bidirectional two-wire data transmission system employing frequency modulation comprising: a first frequency modulation discriminator disposed in one direction of transmission of said transmission system; and a second frequency modulation discriminator disposed in the other direction of transmission of said transmission system; said one direction of transmission having a lower carrier frequency than said carrier frequency of said other direction of transmission; said first discriminator including a first input for first sine wave frequency modulated by a first pulse modulating signal, first means coupled to said first input to produce two control signals derived from both half-cycles of each oscillation of said first frequency modulated sine waves, a first monostable multivibrator coupled to said first means responsive to said two control signals to produce first output pulses for both half-cycles of each oscillation of said first frequency modulated sine waves, and second means coupled to said first multivibrator to integrate said first output pulses to recover said first modulating signal; and said second discriminator including a second input for second sine waves frequency modulated by a second pulse modulating signal, a third means coupled to said second input to produce a third control signal derived from a selected one of the two halfcycles of each oscillation of said second frequency modulated sine waves, a second monostable multivibrator coupled to said third means responsive to said third control signal to produce second output pulses for said selected one of the two half-cycles of each oscillation of said second frequency modulated sine waves, and fourth means coupled to said second multivibrator to integrate said second output pulses to recover said second modulating signal.
Claim 3
Dependent Claim
81 words
A system according to claim 1, wherein said first multivibrator produces said first output pulses in response to said two control signals at both the positively and negatively directed zero crossings of each oscillation of said first frequency modulated sine waves; and said second multivibrator produces said second output pulses in response to said third control signal only at a selected one of either the positively and negatively directed zero crossings of each oscillation of said second frequency modulaTed sine waves.
Claim 4
Dependent Claim
70 words
A system according to claim 2, wherein said first means includes a first differentiator coupled to said first input to produce one of said two control signals, an inverter coupled to said first input; and a second differentiator coupled to said inverter to produce the other of said two control signals; and said third means includes a third differentiator coupled to said second input to produce said third control signal.
Claim 5
Dependent Claim
67 words
A system according to claim 3, wherein said first means further includes a low pass filter coupled to said first input, and a first preamplifier coupled between said low pass filter and said first differentiator and said inverter; and said third means further includes a high pass filter coupled to said second input, and a second preamplifier coupled between said high pass filter and said third differentiator.
Claim 6
Dependent Claim
38 words
A system according to claim 4, wherein said first multivibrator produces said first output pulses having a constant pulse length and height; and said second multivibrator produces said second output pulses having a constant pulse length and height.
Claim 7
Dependent Claim
56 words
A system according to claim 5, wherein each of said first and second multivibrators includes a supply voltage, and a voltage divider coupled to said supply voltages to provide a reference voltage to compensate for supply voltage variations said voltage divider having a zener diode, and a clamping diode coupled in series to said zener diode.
Claim 8
Dependent Claim
58 words
A system according to claim 6, wherein each of said first and second multivibrators includes a pair of interconnected transistors, a timing circuit incorporating one of said pair of transistors, and a diode coupled to base-emitter circuit of said one of said pair of transistors to compensate for temperature variations of the saturation voltage of said base-emitter circuit.
Claim 9
Dependent Claim
72 words
A system according to claim 7, wherein each of said first and second multivibrators includes said timing circuit further having a capacitor connected to the base of said one of said pair of transistors, and a resistor connected to the base of said one of said pair of transistor, said capacitor being a mica capacitor and said resistor being a metal film resistor to compensate for temperature variations in said timing circuit.
Claim 10
Dependent Claim
55 words
A system according to claim 1, wherein a ratio of 1:n exists between said carrier frequency of said one direction of transmission and said carrier frequency of said other direction of transmission, and the widths of said first and second output pulses have a ratio of n:2, where n is an integer greater than one.
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) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |