Patent US4368356A successfully refreshed from Google Patents.
US4368356A
Expired / Lapsed
US
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Pilot tone detector utilizing phase deviation signals
Assignee: Motorola Solutions Inc
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Filing: 1981-03-20
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Granted: 1983-01-11
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Expires: 2001-03-20
Abstract
Abstract An AM stereophonic pilot tone is detected using two signals derived from a received broadcast signal. One signal is proportional to the phase deviation and one is a two-level signal which is a function of the magnitude of the phase deviation. The detector controls activation of the visual indicator, muting of the stereo channel of mono/stereo mode switching with almost complete elimination of false detections during monophonic transmission and poor stereo transmission.
Inventors
- 👤 Lawrence M. Ecklund
- 👤 Frank Drong, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 08:20
CPC Classifications
H; H04; H04H; H04H20/00; H04H20/44; H04H20/46; H04H20/47; H04H20/49
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
205 words
A pilot tone detector for detecting a predetermined frequency when present in a received AM stereophonic signal and comprising: a first input means for providing an audio input signal which is proportional to the phase deviation φ of the received signal; a second input means for providing a second input signal which is a function of the magnitude of the phase deviation of the received signal; filter means coupled to the first input means for providing an output signal essentially limited to the predetermined received frequency; first circuit means coupled to control the output of the filter means in response to a first control signal; second circuit means coupled to receive the controlled output signal of the filter means for rectifying and integrating said output signal and providing a second controlled output signal in response thereto; a reference voltage source; comparator means coupled to receive the second controlled signal and the reference voltage for providing a third controlled signal in response thereto; an indicator means coupled to the comparator means for being controlled by the third controlled signal; and third circuit means coupled to the second input means for processing the second input signal for providing the first control signal to the first circuit means.
Claim 2
Dependent Claim
205 words
A pilot tone detector for detecting a predetermined frequency when present in a received AM stereophonic signal and comprising: a first input means for providing an audio input signal which is proportional to the phase deviation φ of the received signal; a second input means for providing a second input signal which is a function of the magnitude of the phase deviation of the received signal; filter means coupled to the first input means for providing an output signal essentially limited to the predetermined received frequency; first circuit means coupled to control the output of the filter means in response to a first control signal; second circuit means coupled to receive the controlled output signal of the filter means for rectifying and integrating said output signal and providing a second controlled output signal in response thereto; a reference voltage source; comparator means coupled to receive the second controlled signal and the reference voltage for providing a third controlled signal in response thereto; an indicator means coupled to the comparator means for being controlled by the third controlled signal; and third circuit means coupled to the second input means for processing the second input signal for providing the first control signal to the first circuit means.
Claim 3
Dependent Claim
28 words
A pilot tone detector in accordance with claim 1, wherein the second input signal is a two-level signal which changes level at a predetermined value of phase deviation.
Claim 4
Dependent Claim
32 words
A pilot tone detector in accordance with claim 1, wherein the filter means includes an active filter/amplifier and further wherein the gain of the amplifier is controlled by the first control signal.
Claim 5
Dependent Claim
17 words
A pilot tone detector in accordance with claim 1, wherein the indicator means is a visual indicator.
Claim 6
Dependent Claim
34 words
A pilot tone detector in accordance with claim 1, wherein the third circuit means includes means for shaping the second input signal to provide a first control signal having a fast attack/slow decay characteristic.
Claim 7
Dependent Claim
242 words
A pilot tone detector for detecting a predetermined frequency PT when present in a received AM stereophonic signal of the form (1+L+R) cos (w c t+φ) where L and R are intelligence signals, w c t is the carrier, and φ is arc tan [(L+R+PT)/(1+L+R)] and PT is a single frequency stereo presence signal, and comprising: a first input means for providing a audio input signal which is proportional to the phase deviation φ of the received signal; a second input means for providing a second input signal which is a function of the magnitude of the phase deviation of the received signal; filter means coupled to the first input means for providing an output signal essentially limited to the predetermined received frequency; first circuit means coupled to control the output of the filter means in response to a first control signal; second circuit means coupled to receive the controlled output signal of the filter means for rectifying and integrating said output signal and providing a second controlled output signal in response thereto; a reference voltage source; comparator means coupled to receive the second controlled signal and the reference voltage for providing a third controlled signal in response thereto; an indicator means coupled to the comparator means for being controlled by the third controlled signal; and third circuit means coupled to the second input means for processing the second input signal for providing the first control signal to the first circuit means.
Claim 8
Dependent Claim
242 words
A pilot tone detector for detecting a predetermined frequency PT when present in a received AM stereophonic signal of the form (1+L+R) cos (w c t+φ) where L and R are intelligence signals, w c t is the carrier, and φ is arc tan [(L+R+PT)/(1+L+R)] and PT is a single frequency stereo presence signal, and comprising: a first input means for providing a audio input signal which is proportional to the phase deviation φ of the received signal; a second input means for providing a second input signal which is a function of the magnitude of the phase deviation of the received signal; filter means coupled to the first input means for providing an output signal essentially limited to the predetermined received frequency; first circuit means coupled to control the output of the filter means in response to a first control signal; second circuit means coupled to receive the controlled output signal of the filter means for rectifying and integrating said output signal and providing a second controlled output signal in response thereto; a reference voltage source; comparator means coupled to receive the second controlled signal and the reference voltage for providing a third controlled signal in response thereto; an indicator means coupled to the comparator means for being controlled by the third controlled signal; and third circuit means coupled to the second input means for processing the second input signal for providing the first control signal to the first circuit means.
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) | 1986-01-10 | 1986-07-12 | 1987-01-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-01-10 | 1990-07-12 | 1991-01-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-01-10 | 1994-07-12 | 1995-01-11 | $7700.00 | Window Closed / Lapsed |