Patent US3569840A successfully refreshed from Google Patents.
US3569840A
Expired / Lapsed
US
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Carrier squelch scheme
Assignee: Meritor Automotive Canada Inc
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Filing: 1968-10-04
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Granted: 1971-03-09
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Expires: 1988-10-04
Abstract
Abstract A carrier squelch system monitoring both an AGC voltage developed in a superheterodyne receiver and the signal level present in the receiver as represented by the IF carrier signal, with inverse variation of the gain of an AC amplifier in the squelch circuit under control of the AGC voltage, developed out of the IF section of the receiver, in the squelch circuit, and with the IF staging such that the receiver is normally in hard AGC with noise input alone. The additional stages of amplification through the squelch circuit are AC signal amplification stages with temperature change and supply voltage level change induced operational variations minimized.
Inventors
- 👤 Edward H Tanaka
- 👤 James C Riach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:22
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/341
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
243 words
In a radio receiver, with an RF amplifier; a signal mixer; an injection frequency source; an IF amplifier; a detector having an audio output and an IF carrier signal rectified DC output; an AGC circuit developing an AGC voltage with the IF carrier signal rectified DC output signal out of the detector and with an AGC voltage circuit gain control connection back to at least one of said amplifiers; an audio circuit connected to the audio output of said detector; and gating means in the audio signal path of the radio receiver after said detector: a squelch circuit having, a gain controlled amplifier with a connection to the AGC circuit for receiving AGC voltage as a gain controlling input, and a connection to the IF signal path as an additional input to the squelch circuit; and with the squelch circuit connected to said gating means for squelch control of the receiver wherein, the connection to the squelch circuit from the radio receiver IF signal path is a carrier AC signal input connection to the gain controlled amplifier as a first amplifier stage of the squelch circuit; and with connection of the gain controlled amplifier to the AGC circuit being an input connection to bias circuit means of said first amplifier stage of the squelch circuit for inverse gain variation control of said first amplifier stage of the squelch circuit from gain variation of a radio receiver amplifier subject to the AGC gain control.
Claim 2
Dependent Claim
243 words
In a radio receiver, with an RF amplifier; a signal mixer; an injection frequency source; an IF amplifier; a detector having an audio output and an IF carrier signal rectified DC output; an AGC circuit developing an AGC voltage with the IF carrier signal rectified DC output signal out of the detector and with an AGC voltage circuit gain control connection back to at least one of said amplifiers; an audio circuit connected to the audio output of said detector; and gating means in the audio signal path of the radio receiver after said detector: a squelch circuit having, a gain controlled amplifier with a connection to the AGC circuit for receiving AGC voltage as a gain controlling input, and a connection to the IF signal path as an additional input to the squelch circuit; and with the squelch circuit connected to said gating means for squelch control of the receiver wherein, the connection to the squelch circuit from the radio receiver IF signal path is a carrier AC signal input connection to the gain controlled amplifier as a first amplifier stage of the squelch circuit; and with connection of the gain controlled amplifier to the AGC circuit being an input connection to bias circuit means of said first amplifier stage of the squelch circuit for inverse gain variation control of said first amplifier stage of the squelch circuit from gain variation of a radio receiver amplifier subject to the AGC gain control.
Claim 3
Dependent Claim
16 words
The radio receiver of claim 1 wherein, a voltage supply is provided for the squelch circuit.
Claim 4
Dependent Claim
32 words
The radio receiver of claim 2 wherein, a voltage supply connection is provided for said bias circuit means of said first amplifier stage in addition to the AGC circuit voltage input connection.
Claim 5
Dependent Claim
22 words
The radio receiver of claim 3 wherein, said voltage supply is a regulated voltage supply for at least said first amplifier stage.
Claim 6
Dependent Claim
53 words
The radio receiver of claim 3 wherein, said squelch circuit includes, in addition to said first amplifier stage and a DC voltage supply, in successive circuit connected relation: a carrier frequency amplifier; a half-wave rectifier; and trigger circuit means having a squelch gate controlling output connection to said gating means of the receiver.
Claim 7
Dependent Claim
58 words
The radio receiver of claim 5, wherein, the gating means of the receiver and the squelch gate controlling output connection includes a diode in a circuit interconnect between the squelch circuit and the audio output circuit path means of said receiver; and with the diode being subject to DC voltage bias determined conduction for controlling said gate means.
Claim 8
Dependent Claim
52 words
The radio receiver of claim 6 wherein, said gate means includes a transistor with the base to emitter junction in the audio signal path; and with said diOde circuit connected to said transistor as to provide reverse biasing of said transistor base to emitter junction and thereby squelching of the receiver audio.
Claim 9
Dependent Claim
20 words
The radio receiver of claim 5 wherein, said trigger circuit means of the squelch circuit is a Schmidt trigger circuit.
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) | 1974-03-08 | 1974-09-07 | 1975-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-08 | 1978-09-07 | 1979-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-08 | 1982-09-07 | 1983-03-09 | $7700.00 | Window Closed / Lapsed |