US3628058A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Integrated dual time constant squelch circuit
Assignee: Motorola Solutions Inc
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Filing: 1970-02-24
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Granted: 1971-12-14
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Expires: 1990-02-24
Abstract
Abstract An integrated circuit dual time constant squelch circuit for eliminating squelch tail includes a short time constant ripple filter which produces a filtered noise voltage which is applied to the inputs three differential switch circuits actuated at three different threshold levels. The differential switch with the lowest threshold level establishes the minimum detected noise voltage to which the circuit responds and, upon actuation, charges a long time constant storage capacitor to a value exceeding a second threshold of a second of the differential switch circuits used as an output switch and having the capacitor connected to a second input thereof. The third differential switch circuit is actuated when a third, higher, threshold level is exceeded by the detected noise voltage and operates to disable the output of the second differential switch at strong signal levels, thereby switching control of the circuit solely to the short time constant ripple filter.
Inventors
- 👤 Roy H Espe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 09:48
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
276 words
A squelch filter circuit operated in response to a detected noise voltage including in combination: filter means having a particular time constant and adapted to receive the detected noise voltage, and having an output and being responsive to the detected noise voltage to develop a filtered noise voltage at said output; first switch means having input means and an output and responsive to an input voltage greater than a first predetermined threshold to be actuated thereby; means coupling said output of said filter means with said input means of said first switch means; second switch means having an input and an output and responsive to an input voltage greater than a second predetermined threshold which is less than said first predetermined threshold to be actuated thereby; means coupling said output of said filter means to said input of said second switch means; charge storage means having a time constant greater than said particular time constant coupled with said output of the second switch means for storing a predetermined charge in response to actuation of said second switch means, said predetermined charge producing a voltage greater than said first predetermined threshold; circuit means coupling said charge storage means with said input means of said first switch means; third switch means having an input and an output and responsive to an input voltage greater than a predetermined threshold which is equal to or greater than said first predetermined threshold to be actuated thereby; means coupling said filter means to said input of said third switch means; and means coupled to said output of said third switch means and responsive to actuation thereof for disabling said charge storage means.
Claim 2
Dependent Claim
276 words
A squelch filter circuit operated in response to a detected noise voltage including in combination: filter means having a particular time constant and adapted to receive the detected noise voltage, and having an output and being responsive to the detected noise voltage to develop a filtered noise voltage at said output; first switch means having input means and an output and responsive to an input voltage greater than a first predetermined threshold to be actuated thereby; means coupling said output of said filter means with said input means of said first switch means; second switch means having an input and an output and responsive to an input voltage greater than a second predetermined threshold which is less than said first predetermined threshold to be actuated thereby; means coupling said output of said filter means to said input of said second switch means; charge storage means having a time constant greater than said particular time constant coupled with said output of the second switch means for storing a predetermined charge in response to actuation of said second switch means, said predetermined charge producing a voltage greater than said first predetermined threshold; circuit means coupling said charge storage means with said input means of said first switch means; third switch means having an input and an output and responsive to an input voltage greater than a predetermined threshold which is equal to or greater than said first predetermined threshold to be actuated thereby; means coupling said filter means to said input of said third switch means; and means coupled to said output of said third switch means and responsive to actuation thereof for disabling said charge storage means.
Claim 3
Dependent Claim
25 words
The combination according to claim 1 wherein the predetermined threshold of said third switch means is greater than both said first and second predetermined thresholds.
Claim 4
Dependent Claim
45 words
The combination according to claim 2 further including resistor means coupling the output of said second switch means with said charge storage means for providing a predetermined time delay following actuation of said second switch means before said charge storage means stores said predetermined charge.
Claim 5
Dependent Claim
36 words
The combination according to claim 1 wherein the means responsive to actuation of said third switch means for disabling said charge storage means renders said charge storage means nonresponsive to actuation of said second switch means.
Claim 6
Dependent Claim
44 words
The combination according to claim 1 further including reference voltage means, wherein said first, second, and third switch means are comparator circuits, with the thresholds of said first, second and third comparator circuits being determined by reference voltages obtained from said reference voltage means.
Claim 7
Dependent Claim
14 words
The combination according to claim 5 wherein said comparator circuits are differential amplifier circuits.
Claim 8
Dependent Claim
26 words
The combination according to claim 6 wherein the predetermined threshold of said third differential amplifier circuit is greater than both said first and second predetermined thresholds.
Claim 9
Dependent Claim
135 words
The combination according to claim 1 wherein said charge storage means includes storage capacitor means and first and second charging path means connected to said storage capacitor means, said first charging path means being enabled by actuation of said second switch means to couple said capacitor means with a source of charging potential, said second charging path means having at least a portion thereof different from said first charging path means and further having a higher impedance than said first charging path means, with said higher impedance being of such a Value as to cause the discharge of said capacitor means through said second charging path means to have a time constant greater than said particular time constant, and wherein said means for disabling said charge storage means operates to disable said first charging path.
Claim 10
Dependent Claim
99 words
The combination according to claim 8 wherein said first charging path means includes an emitter follower circuit connected between said capacitor means and a source of reference potential and having an input, means connecting said output of said second switch means to said input of said emitter follower circuit for rendering the same conductive in response to actuation of said second switch means, and wherein said means responsive to actuation of said third switch means provides a signal coupled to said input of said emitter follower circuit for rendering the same nonconductive and nonresponsive to said second switch means.
Claim 11
Dependent Claim
142 words
The combination according to claim 9 wherein said first, second and third switch means each are transistor differential amplifiers operated as differential switch means and each having an input, wherein the predetermined thresholds are established by voltage reference means providing reference voltages to each of said first, second and third differential switch means respectively, the detected noise voltage being applied to an input of each of said first, second and third differential switch means to actuate the same whenever the reference voltage applied to the corresponding switch means is exceeded by the filtered noise voltage, actuation of said second differential switch means rendering said emitter follower circuit conductive to charge said capacitor means to the same predetermined voltage irrespective of the voltage applied to said input of said second differential switch means once the threshold voltage reference level thereof has been exceeded.
Claim 12
Dependent Claim
65 words
The combination according to claim 10 wherein said means for rendering said emitter follower circuit nonconductive includes normally nonconductive transistor means responsive to actuation of said third differential switch means for shunting said input of said emitter follower circuit thereby rendering it nonconductive and nonresponsive to the output of said second differential switch means to interrupt said first charging path means for said capacitor means.
Claim 13
Dependent Claim
212 words
A squelch filter circuit operated in response to a detected noise voltage including in combination: filter means having a particular time constant and adapted to receive the detected noise voltage, and having an output and being responsive to the detected noise voltage to develop a filtered noise voltage at said output; first switch means having an input and an output and responsive to an input voltage greater than a predetermined threshold to be actuated thereby; means coupling said output of said filter means to said input of said first switch means; charge storage means having a time constant greater than said particular time constant coupled with said output of said first switch means for storing a predetermined charge in response to actuation of said first switch means; second switch means having input means and an output, with said input means coupled with said charge storage means for operating said second switch means in response to the predetermined charge; means coupling said output of said filter means to said input means of said second switch means for controlling the same in response to a detected noise voltage which exceeds a second threshold greater than said predetermined threshold; and squelch control means connected to said output of said second switch means and controlled thereby.
Claim 14
Dependent Claim
212 words
A squelch filter circuit operated in response to a detected noise voltage including in combination: filter means having a particular time constant and adapted to receive the detected noise voltage, and having an output and being responsive to the detected noise voltage to develop a filtered noise voltage at said output; first switch means having an input and an output and responsive to an input voltage greater than a predetermined threshold to be actuated thereby; means coupling said output of said filter means to said input of said first switch means; charge storage means having a time constant greater than said particular time constant coupled with said output of said first switch means for storing a predetermined charge in response to actuation of said first switch means; second switch means having input means and an output, with said input means coupled with said charge storage means for operating said second switch means in response to the predetermined charge; means coupling said output of said filter means to said input means of said second switch means for controlling the same in response to a detected noise voltage which exceeds a second threshold greater than said predetermined threshold; and squelch control means connected to said output of said second switch means and controlled thereby.
Claim 15
Dependent Claim
120 words
The combination according to claim 12 wherein said charge storage means includes storage capacitor means and first and second charging path means connected to said storage capacitor means, said first charging path means being enabled by actuation of said first switch means to couple said storage capacitor means with a source of cHarging potential, said second charging path means having at least a portion thereof different from said first charging path means and further having a higher impedance than said first charging path means, with said higher impedance being of such a value as to cause the discharge of said storage capacitor means through said second charging path means to have a time constant greater than said particular time constant.
Claim 16
Dependent Claim
43 words
The combination according to claim 13 wherein said first charging path means includes an emitter follower connected between said storage capacitor means and a source of reference potential, said emitter follower being rendered conductive in response to actuation of said first switch means.
Claim 17
Dependent Claim
20 words
The combination according to claim 1 further including squelch control means connected to said output of said first switch means.
Claim 18
Dependent Claim
252 words
A squelch filter circuit operated in response to a detected noise voltage including in combination: filter means adapted to receive the detected noise voltage having a particular time constant and having an output, and being responsive to the detected noise voltage to develop a filtered noise voltage at said output; first comparator means having input means and an output and responsive to an input voltage greater than a first predetermined threshold to be actuated thereby; means coupling said output of said filter means with said input means of said first comparator means; second comparator means having an input and an output and responsive to an input voltage greater than a second predetermined threshold which is less than said first predetermined threshold to be actuated thereby; means coupling said output of said filter means to said input of said second comparator means; charge storage means having a time constant greater than said particular time constant coupled with said output of the second comparator means for storing a predetermined charge in response to actuation of said second comparator means, said predetermined charge producing a voltage greater than said first predetermined threshold; circuit means coupling said charge storage means with said input means of said first comparator means; control means having an input and an output with said input coupled to said filter means for receiving the filtered noise voltage; and means coupling said output of said control means to said charge storage means for controlling the same in response to the filtered noise voltage.
Claim 19
Dependent Claim
252 words
A squelch filter circuit operated in response to a detected noise voltage including in combination: filter means adapted to receive the detected noise voltage having a particular time constant and having an output, and being responsive to the detected noise voltage to develop a filtered noise voltage at said output; first comparator means having input means and an output and responsive to an input voltage greater than a first predetermined threshold to be actuated thereby; means coupling said output of said filter means with said input means of said first comparator means; second comparator means having an input and an output and responsive to an input voltage greater than a second predetermined threshold which is less than said first predetermined threshold to be actuated thereby; means coupling said output of said filter means to said input of said second comparator means; charge storage means having a time constant greater than said particular time constant coupled with said output of the second comparator means for storing a predetermined charge in response to actuation of said second comparator means, said predetermined charge producing a voltage greater than said first predetermined threshold; circuit means coupling said charge storage means with said input means of said first comparator means; control means having an input and an output with said input coupled to said filter means for receiving the filtered noise voltage; and means coupling said output of said control means to said charge storage means for controlling the same in response to the filtered noise voltage.
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) | 1974-12-13 | 1975-06-14 | 1975-12-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-13 | 1979-06-14 | 1979-12-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-13 | 1983-06-14 | 1983-12-14 | $7700.00 | Window Closed / Lapsed |