US4411021A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic threshold squelch
Assignee: Motorola Solutions Inc
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Filing: 1981-07-27
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Granted: 1983-10-18
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Expires: 2001-07-27
Abstract
Abstract An automatic threshold squelch circuit, responsive to noise signals from the receiver demodulator, having automatic means for setting the squelch level. A noise detector is coupled to the demodulator and to a comparator and sample and hold circuit such that a predetermined portion of the detected noise signal level is stored in the sample and hold circuit when no signal is being received. The stored noise level is then compared to the detected noise signal from the noise detector and a mute signal is generated in response to the detected noise level exceeding the stored signal level.
Inventors
- 👤 John H. Yoakum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:27
CPC Classifications
H; H03; H03G; H03G11/00; H03G11/04; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/344
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
125 words
An automatic threshold squelch circuit, for radio receiver having a demodulator responsive to noise signals from the receiver demodulator for generating a mute signal when no transmission is being received by the receiver, said squelch circuit comprising: noise detector means for producing a unidirectional signal level as a function of the noise signal from the demodulator; memory means, coupled to the noise detector means, for sampling and storing the unidirectional signal level when no transmissions are being received by the receiver; comparator means, coupled to the detector means and the memory means, for comparing the unidirectional signal level from the noise detector means to the stored signal level, and generating an unmute signal when the uni-directional signal level is less than the store signal level.
Claim 2
Dependent Claim
125 words
An automatic threshold squelch circuit, for radio receiver having a demodulator responsive to noise signals from the receiver demodulator for generating a mute signal when no transmission is being received by the receiver, said squelch circuit comprising: noise detector means for producing a unidirectional signal level as a function of the noise signal from the demodulator; memory means, coupled to the noise detector means, for sampling and storing the unidirectional signal level when no transmissions are being received by the receiver; comparator means, coupled to the detector means and the memory means, for comparing the unidirectional signal level from the noise detector means to the stored signal level, and generating an unmute signal when the uni-directional signal level is less than the store signal level.
Claim 3
Dependent Claim
36 words
The automatic threshold squelch circuit of claim 1, further comprising attenuation means, coupled to the noise detector means and the memory means, for attenuating signals coupled therethrough from the noise detector means by a predetermined amount.
Claim 4
Dependent Claim
45 words
The automatic threshold squelch circuit of claim 1 or 2 further comprising timing means, coupled to the receiver, for disabling reception of transmissions for a predetermined period of time following receiver turn on, thereby permitting the memory means to store an initial unidirectional signal level.
Claim 5
Dependent Claim
19 words
The automatic threshold squelch circuit of claim 3, wherein the memory means comprises an analog sample and hold circuit.
Claim 6
Dependent Claim
19 words
The automatic threshold squelch circuit of claim 3, wherein the memory means comprises a digital sample and hold circuit.
Claim 7
Dependent Claim
37 words
The automatic threshold squelch circuit of claim 1, further comprising filter means, coupled to the demodulator and the noise detector means, for filtering the noise signals and coupling the filtered noise signals to the noise detector means.
Claim 8
Dependent Claim
111 words
Communications receiving apparatus which operates in response to incoming signals, comprising: radio receiver apparatus including RF, mixer, IF, demodulator, and audio sections; noise detector means for producing a unidirectional signal level in response to noise signals from the receiver demodulator; memory means having an input coupled to the noise detector means, for storing the unidirectional signal of the highest level applied to the memory means input; comparator means, coupled to the detector means and the memory means, for comparing the unidirectional signal level from the noise detector means to the stored signal level and for generating an unmute signal when the uni-directional signal level is less than the stored signal level.
Claim 9
Dependent Claim
111 words
Communications receiving apparatus which operates in response to incoming signals, comprising: radio receiver apparatus including RF, mixer, IF, demodulator, and audio sections; noise detector means for producing a unidirectional signal level in response to noise signals from the receiver demodulator; memory means having an input coupled to the noise detector means, for storing the unidirectional signal of the highest level applied to the memory means input; comparator means, coupled to the detector means and the memory means, for comparing the unidirectional signal level from the noise detector means to the stored signal level and for generating an unmute signal when the uni-directional signal level is less than the stored signal level.
Claim 10
Dependent Claim
30 words
The communications receiving apparatus of claim 7, further comprising timing means coupled to the mixer section for disabling the mixer for a predetermined period of time following receiver turn on.
Claim 11
Dependent Claim
37 words
The communications receiving apparatus of claim 7 or 8 further comprising attenuation means, coupled to the noise detector means and the memory means, for attenuating signals coupled therethrough from the noise detector means by a predetermined amount.
Claim 12
Dependent Claim
48 words
The communications receiving apparatus of claim 7 or 8, further comprising a squelch gate, for coupling the demodulated audio signals from the demodulator section to the audio section, in response to the unmute signal and for inhibiting said demodulated audio signals in the absence of the unmute signal.
Claim 13
Dependent Claim
81 words
In communications receiving apparatus having a demodulator, a method of providing automatic squelch, comprising the steps of: (a) producing a unidirectional signal level as a function of a noise signal level from the receiver demodulator; (b) storing the unidirectional signal level in response to a predetermined condition producing a stored signal level; (c) comparing the unidirectional signal level to the stored signal level and generating a squelch control signal when the unidirectional signal level is less than the stored signal level.
Claim 14
Dependent Claim
81 words
In communications receiving apparatus having a demodulator, a method of providing automatic squelch, comprising the steps of: (a) producing a unidirectional signal level as a function of a noise signal level from the receiver demodulator; (b) storing the unidirectional signal level in response to a predetermined condition producing a stored signal level; (c) comparing the unidirectional signal level to the stored signal level and generating a squelch control signal when the unidirectional signal level is less than the stored signal level.
Claim 15
Dependent Claim
26 words
The method of claim 11 wherein the storing step (b) comprises storing the unidirectional signal level when there is no transmission being received by the receiver.
Claim 16
Dependent Claim
19 words
The method of claim 12 further comprising the step of attenuating the unidirectional signal level by a predetermined amount.
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) | 1986-10-17 | 1987-04-18 | 1987-10-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-10-17 | 1991-04-18 | 1991-10-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-10-17 | 1995-04-18 | 1995-10-18 | $7700.00 | Window Closed / Lapsed |