Patent US3755741A successfully refreshed from Google Patents.
US3755741A
Expired / Lapsed
US
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Self-monitoring of radio receivers
Assignee: Collins Radio Co
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Filing: 1972-02-11
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Granted: 1973-08-28
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Expires: 1992-02-11
Abstract
Abstract Continuous monitoring of a radio receiver without impairing normal receiver operation is provided by an internally generated carrier signal combined at low level with the received signal. The test carrier is so modulated as to not affect normal receiver detection process, and the test modulation signal component, as present in the output of the receiver detector, is synchronously demodulated and monitored to provide indication of faulty receiver threshold level and signal distortion.
Inventors
- 👤 H Stover
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:00
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
195 words
In a radio receiver of the type comprising RF amplifying means receiving an input signal, an injection oscillator and signal mixer converting said received signal to an intermediate frequency signal, and signal detecting means receiving said intermediate frequency signal and detecting the modulation intelligence, means for continuously moniToring the performance of said receiver as to faulty threshold level and signal distortion without interference with normal receiver operation comprising signal generating means for generating an internal carrier signal with frequency equal that of the carrier frequency to which said receiver is tuned, means for modulating said internally generated carrier signal by a controlled pattern modulating signal the average detected amplitude of which is zero, means for combining a predetermined level of said pattern modulated internally generated carrier signal with said input signal, said level being substantially below that of the noise level of said receiver, synchronous demodulation means receiving the output of said signal detecting means and said modulating signal as respective inputs thereto, means for averaging the output of said synchronous demodulation means, and threshold sensitive annunciating means responsive to a predetermined level of the output from said means for averaging to be activated thereby.
Claim 2
Dependent Claim
195 words
In a radio receiver of the type comprising RF amplifying means receiving an input signal, an injection oscillator and signal mixer converting said received signal to an intermediate frequency signal, and signal detecting means receiving said intermediate frequency signal and detecting the modulation intelligence, means for continuously moniToring the performance of said receiver as to faulty threshold level and signal distortion without interference with normal receiver operation comprising signal generating means for generating an internal carrier signal with frequency equal that of the carrier frequency to which said receiver is tuned, means for modulating said internally generated carrier signal by a controlled pattern modulating signal the average detected amplitude of which is zero, means for combining a predetermined level of said pattern modulated internally generated carrier signal with said input signal, said level being substantially below that of the noise level of said receiver, synchronous demodulation means receiving the output of said signal detecting means and said modulating signal as respective inputs thereto, means for averaging the output of said synchronous demodulation means, and threshold sensitive annunciating means responsive to a predetermined level of the output from said means for averaging to be activated thereby.
Claim 3
Dependent Claim
22 words
Monitoring means as defined in claim 1 wherein said controlled pattern modulating signal comprises the output signal from a square wave generator.
Claim 4
Dependent Claim
35 words
Monitoring means as defined in claim 1 wherein said controlled pattern modulating signal comprises the output from a means for repetitively generating a pseudo-random bi-level signal pattern of predetermined bit length and the inverse thereof.
Claim 5
Dependent Claim
39 words
Means as defined in claim 1 wherein said modulating signal comprises an alternating current signal and means for keying said internally generated carrier signal for combination with said received signal during successive half cycles of said alternating current signal.
Claim 6
Dependent Claim
119 words
Monitoring means as defined in claim 1 wherein said modulating signal comprises the output from a subcarrier oscillator, a subcarrier modulating waveform generator, means for modulating said subcarrier oscillator output with the output from said subcarrier modulation waveform generator whereby the frequency of subcarrier oscillator varies as a function of the output waveform from said subcarrier modulation waveform generator on a repetitive pattern basis, and further comprising subcarrier demodulator means receiving the output from said synchronous demodulator and said subcarrier modulation waveform generator, a further threshold detector responsive to a predetermined output level from said subcarrier demodulation to provide an output signal, said annunciating means being further responsive to an output from said further threshold detector to be activated.
Claim 7
Dependent Claim
22 words
Means as defined in claim 5 wherein the output from said subcarrier modulator waveform generator comprises a waveform with zero average value.
Claim 8
Dependent Claim
42 words
Means as defined in claim 6 further comprising means for detecting the presence of an AC component in the output of said synchronous demodulator and means for additionally activating said annunciator in response to a predetermined threshold of said detected AC component.
Claim 9
Dependent Claim
115 words
Monitoring means as defined in claim 1 wherein said modulating signal comprises the output from an audio test signal generator, and further comprising signal gain control means receiving the output from said receiver detector, differential amplifier means receiving the output from said audio test signal generator and the output from said gain control means as respective mutually subtractive inputs thereto, further synchronous demodulator means receiving the output of said differential amplifier and the output of said audio test signal generator as respective inputs thereto, a further threshold detector receiving the output of said further synchronous demodulator means, and said annunciating means being further responsive to the output from said further threshold detector to be activated.
Claim 10
Dependent Claim
161 words
Monitoring means as defined in claim 1 wherein said modulating signal comprises the output from a balanced modulator, means for generating a first input to said balanced modulator comprising a signal source frequency modulated at a predetErmined modulation rate, means generating a second input to said balanced modulator comprising a low frequency tone, said monitoring means further comprising a further synchronous demodulator receiving the output of said receiver detector and a signal at twice the frequency of said low frequency tone as respective inputs thereto, said annunciating means being additionally responsive to a predetermined threshold of the output of said further synchronous demodulator to be activated; a still further synchronous demodulator receiving the output of said receiver detector and a signal equal in frequency to the modulation rate of said frequency modulated signal source as respective inputs thereto, and said annunicating means being additionally responsive to a predetermined threshold of the output from said still further synchronous demodulator to be activated.
Claim 11
Dependent Claim
87 words
A system as defined in claim 1 wherein said means for generating said internally generated carrier signal comprises an oscillator operating at a frequency displaced from that of the carrier frequency of the signal to which said receiver is tuned by the instant frequency of said receiver injection oscillator, signal mixing means receiving the output of said oscillator and the output of said receiver injection oscillator, and filter means receiving the output of said signal mixing means and providing an output comprising said internally generated carrier signal.
Claim 12
Dependent Claim
38 words
Means for monitoring as defined in claim 10 wherein said means for combining comprises signal attenuating means operable to establish the level of the output signal from said means for combining as combined with said receiver input signal.
Claim 13
Dependent Claim
70 words
Monitoring means as defined in claim 11 wherein said receiver comprises automatic gain control means including an automatic gain control detector and amplifier the output from which is utilized to maintain a constant level input to said receiver detector with variations in received signal amplitude; said attenuator means being voltage controlled, and means for varying the attenuation effected by said attenuator means as an inverse function of said AGC voltage.
Claim 14
Dependent Claim
67 words
Monitoring means as defined in claim 12 wherein said voltage controlled attenuating means is responsive to said AGC control voltage to effect a level of said pattern modulated internally generated signal as combined with said receiver input signal so as to increase the signal level combined in proportion to increasing input signal levels and not exceeding a level substantially less than that of said receiver noise level.
Claim 15
Dependent Claim
59 words
Monitoring means as defined in claim 13 wherein said threshold detector provides an output signal of predetermined magnitude for input signal level in excess of a predetermined threshold, signal inverting means receiving the output of said threshold detector, said annunicator being activated to indicate receiver inoperability upon the output of said inverting means being below a predetermined threshold value.
Claim 16
Dependent Claim
54 words
Monitoring means as defined in claim 14 further comprising signal gating means receiving the output of said inverting means, time delay means responsive to energization of said receiver to enable said gating means a predetermined period of time after said energization, and the output of said gating means being applied to said annunciating means.
Claim 17
Dependent Claim
38 words
Monitoring means as defined in claim 15 wherein said controlled pattern modulated signal from said internal signal generating means is combined with said received signal at a level not exceeding one-tenth of the noise level of said receiver.
Claim 18
Dependent Claim
22 words
Monitoring means as defined in claim 13 wherein said controlled pattern modulating signal comprises the output signal from a square wave generator.
Claim 19
Dependent Claim
35 words
Monitoring means as defined in claim 13 wherein said controlled pattern modulating signal comprises the output from a means for repetitively generating a pseudo-random bi-level signal pattern of predetermined bit length and the inverse thereof.
Claim 20
Dependent Claim
39 words
Means as defined in claIm 13 wherein said modulating signal comprises an alternating current signal and means for keying said internally generated carrier signal for combination with said received signal during successive half cycles of said alternating current signal.
Claim 21
Dependent Claim
118 words
Monitoring means as defined in claim 13 wherein said modulating signal comprises the output from a subcarrier, a subcarrier modulating waveform generator, means for modulating said subcarrier oscillator output with the output from said subcarrier modulation waveform generator whereby the frequency of subcarrier oscillator varies as a function of the output waveform from said subcarrier modulation waveform generator on a repetitive pattern basis, and further comprising subcarrier demodulator means receiving the output from said synchronous demodulator and said subcarrier modulation waveform generator, a further threshold detector responsive to a predetermined output level from said subcarrier demodulation to provide an output signal, said annunciating means being further responsive to an output from said further threshold detector to be activated.
Claim 22
Dependent Claim
22 words
Means as defined in claim 20 wherein the output from said subcarrier modulator waveform generator comprises a waveform with zero average value.
Claim 23
Dependent Claim
42 words
Means as defined in claim 21 further comprising means for detecting the presence of an AC component in the output of said synchronous demodulator and means for additionally activating said annunciator in response to a predetermined threshold of said detected AC component.
Claim 24
Dependent Claim
115 words
Monitoring means as defined in claim 13 wherein said modulating signal comprises the output from an audio test signal generator, and further comprising signal gain control means receiving the output from said receiver detector, differential amplifier means receiving the output from said audio test signal generator and the output from said gain control means as respective mutually subtractive inputs thereto, further synchronous demodulator means receiving the output of said differential amplifier and the output of said audio test signal generator as respective inputs thereto, a further threshold detector receiving the output of said further synchronous demodulator means, and said annunciating means being further responsive to the output from said further threshold detector to be activated.
Claim 25
Dependent Claim
161 words
Monitoring means as defined in claim 13 wherein said modulating signal comprises the output from a balanced modulator, means for generating a first input to said balanced modulator comprising a signal source frequency modulated at a predetermined modulation rate, means generating a second input to said balanced modulator comprising a low frequency tone, said monitoring means further comprising a further synchronous demodulator receiving the output of said receiver detector and a signal at twice the frequency of said low frequency tone as respective inputs thereto, said annunciating means being additionally responsive to a predetermined threshold of the output of said further synchronous demodulator to be activated; a still further synchronous demodulator receiving the output of said receiver detector and a signal equal in frequency to the modulation rate of said frequency modulated signal source as respective inputs thereto, and said annunciating means being additionally responsive to a predetermined threshold of the output from said still further synchronous demodulator to be activated.
References Cited (Backward Citations)
US3273065A
Cited
US3389392A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |