US3952252A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Noise suppressor for telecommunication system
Assignee: Italtel SpA
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Filing: 1974-01-30
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Granted: 1976-04-20
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Expires: 1994-01-30
Abstract
Abstract A detector stage at a receiving station of a telecommunication system derives from an incoming modulated carrier a constant reference voltage lower than the minimum amplitude of the detected modulation signals which are fed to the base of an NPN transistor whose emitter receives the reference voltage through a resistor. The collector of the transistor, cut off from any direct-current supply, is coupled to a subsequent audio stage through a series capacitor and to ground through a shunt capacitor. Normally, the transistor is saturated and its emitter potential, closely following its base voltage, is practically duplicated on its collector. In the presence of large static, however, the noise pulses cut off the transistor as the shunt capacitor temporarily stores the magnitude of the immediately preceding signal amplitude.
Inventors
- 👤 Carlo Cornacchia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 09:47
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/345; H03G11/00; H03G11/04
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
247 words
A noise suppressor for a telecommunication system, comprising: a receiver having an input circuit for an incoming carrier modulated in amplitude by useful signal pulses and accompanying noise pulses, said receiver also having an output circuit; a source of direct current; rectifying circuit means connected across said source and forming a first terminal provided with a first biasing voltage and a second terminal provided with a second biasing voltage from said source; a transistor between said input and output circuits having a base connected to said first terminal, an emitter connected to said second terminal and a floating collector disconnected from said source, the connection between said emitter and said second terminal including a resistor, the relative polarities of said first and second biasing voltages being such as to drive a base current sufficient to saturate said transistor in the absence of said carrier, said circuit means deriving from the amplitude modulation of said carrier a train of unipolar pulsations superimposed upon said first biasing voltage with a polarity such as to reduce the potential difference between said base and said emitter, said transistor forming a low-impedance path between said emitter and said collector in its saturated state for the passage of limited-amplitude pulsations including said signal pulses but blocking the transmission of pulsations from said base to said collector in the presence of large-amplitude noise pulses reducing said potential difference to substantially zero; and a load terminal in said output stage capacitively coupled to said collector.
Claim 2
Dependent Claim
247 words
A noise suppressor for a telecommunication system, comprising: a receiver having an input circuit for an incoming carrier modulated in amplitude by useful signal pulses and accompanying noise pulses, said receiver also having an output circuit; a source of direct current; rectifying circuit means connected across said source and forming a first terminal provided with a first biasing voltage and a second terminal provided with a second biasing voltage from said source; a transistor between said input and output circuits having a base connected to said first terminal, an emitter connected to said second terminal and a floating collector disconnected from said source, the connection between said emitter and said second terminal including a resistor, the relative polarities of said first and second biasing voltages being such as to drive a base current sufficient to saturate said transistor in the absence of said carrier, said circuit means deriving from the amplitude modulation of said carrier a train of unipolar pulsations superimposed upon said first biasing voltage with a polarity such as to reduce the potential difference between said base and said emitter, said transistor forming a low-impedance path between said emitter and said collector in its saturated state for the passage of limited-amplitude pulsations including said signal pulses but blocking the transmission of pulsations from said base to said collector in the presence of large-amplitude noise pulses reducing said potential difference to substantially zero; and a load terminal in said output stage capacitively coupled to said collector.
Claim 3
Dependent Claim
23 words
A noise suppressor as defined in claim 1, further comprising a shunt capacitor connected between said collector and a terminal of said source.
Claim 4
Dependent Claim
23 words
A noise suppressor as defined in claim 1 wherein said input and output circuits comprise an intermediate-frequency stage and an audio stage, respectively.
Claim 5
Dependent Claim
51 words
A noise suppressor as defined in claim 1 wherein said circuit means comprises a capacitive branch connected to a terminal of said source, a resistive branch in parallel with said capacitive branch, and a diode in series with both branches, said first terminal being connected to said branches via said diode.
Claim 6
Dependent Claim
23 words
A noise suppressor as defined in claim 4, further comprising a shunt capacitor connected between said collector and said terminal of said source.
Claim 7
Dependent Claim
31 words
A noise suppressor as defined in claim 4, further comprising a bypass capacitor connected across a part of said resistive branch between said second terminal and said terminal of said source.
Claim 8
Dependent Claim
26 words
A noise suppressor as defined in claim 4 wherein said resistive branch comprises a voltage divider, said second terminal being a tap on said voltage divider.
Claim 9
Dependent Claim
42 words
A noise suppressor as defined in claim 7 wherein said circuit means further comprises a low-pass filter including a series inductance between said diode and said first terminal and a shunt capacitance between said first terminal and said terminal of said source.
Claim 10
Dependent Claim
32 words
A noise suppressor as defined in claim 7 further comprising gain-control means for said receiver including comparison means with input connections to said emitter and to a point on said voltage divider.
Claim 11
Dependent Claim
24 words
A noise suppressor as defined in claim 9 wherein said point on said voltage divider lies substantially midway between said diode and said tap.
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) | 1979-04-20 | 1979-10-20 | 1980-04-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-04-20 | 1983-10-20 | 1984-04-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-04-20 | 1987-10-20 | 1988-04-20 | $7700.00 | Window Closed / Lapsed |