US3778704A
Expired / Lapsed
US
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Technique for directly measuring a signal-to-noise ratio of a communication circuit
Assignee: SPX Technologies Inc
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Filing: 1973-04-02
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Granted: 1973-12-11
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Expires: 1993-04-02
Abstract
Abstract A method and apparatus for determining the signal-to-noise characteristic of a communication circuit by first forming a cumulative phase jitter function whose amplitude is proportional to a ratio between magnitudes of a dominant signal and all interfering signals. This phase jitter function is detected by a true r.m.s. detector and a DC output level of the detector is proportional to the signal-to-noise ratio of a communication circuit through which the test signal has been passed.
Inventors
- 👤 A Lubarsky
- 👤 C Volkland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 18:18
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/46
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
112 words
A method of analyzing a desired signal plus noise, comprising the steps of: forming from said desired signal plus noise a function having an amplitude that varies in one direction in response to a period of said signal plus noise being greater than an average period thereof over a large number of cycles and varies in an opposite direction in response to a period of said signal plus noise being less than said average period, and detecting said function to form a test signal that is substantially a r.m.s. value of said varying amplitude function, whereby said r.m.s. signal is an indication of the signal-to-noise ratio of said desired signal plus noise.
Claim 2
Independent Claim
112 words
A method of analyzing a desired signal plus noise, comprising the steps of: forming from said desired signal plus noise a function having an amplitude that varies in one direction in response to a period of said signal plus noise being greater than an average period thereof over a large number of cycles and varies in an opposite direction in response to a period of said signal plus noise being less than said average period, and detecting said function to form a test signal that is substantially a r.m.s. value of said varying amplitude function, whereby said r.m.s. signal is an indication of the signal-to-noise ratio of said desired signal plus noise.
Claim 3
Dependent Claim
31 words
The method of claim 1 which includes the further step of making an inverse log conversion of said R.m.s. signal, whereby a desired signal-to-noise ratio may be expressed directly in decibels.
Claim 4
Independent Claim
117 words
A method of measuring harmonic distortion of an input comprising the steps of: shifting the input signal an incremental frequency, forming from the frequency shifted input signal a function having an amplitude that varies in one direction in response to a period of said frequency shifted signal being greater than an average period thereof over a large number of cycles and varies in an opposite direction in response to a period of said frequency shifted signal being less than said average period, and detecting said function to form a test signal that is substantially a r.m.s. value of said varying amplitude function, whereby said r.m.s. signal is an indication of the harmonic distortion of the input signal.
Claim 5
Independent Claim
117 words
A method of measuring harmonic distortion of an input comprising the steps of: shifting the input signal an incremental frequency, forming from the frequency shifted input signal a function having an amplitude that varies in one direction in response to a period of said frequency shifted signal being greater than an average period thereof over a large number of cycles and varies in an opposite direction in response to a period of said frequency shifted signal being less than said average period, and detecting said function to form a test signal that is substantially a r.m.s. value of said varying amplitude function, whereby said r.m.s. signal is an indication of the harmonic distortion of the input signal.
Claim 6
Independent Claim
159 words
A method of testing a communication circuit, comprising the steps of: inserting a single frequency sinusoidal test signal into an input of said communication circuit, receiving said test signal at an output of said communication circuit in the form of the test signal plus noise, forming from said test signal plus noise a function having an amplitude that varies in one direction in response to a period of said test signal plus noise that is greater than an average period thereof over a number of cycles and which varies in an opposite direction in response to a period of said test signal plus noise that is less than said average period, detecting said function to form a direct current signal that is substantially an r.m.s. value of said varying amplitude function, and taking an inverse logarithm function of said direct current signal in order to form an output signal that is directly related to a signal-to-noise ratio in decibels.
Claim 7
Independent Claim
159 words
A method of testing a communication circuit, comprising the steps of: inserting a single frequency sinusoidal test signal into an input of said communication circuit, receiving said test signal at an output of said communication circuit in the form of the test signal plus noise, forming from said test signal plus noise a function having an amplitude that varies in one direction in response to a period of said test signal plus noise that is greater than an average period thereof over a number of cycles and which varies in an opposite direction in response to a period of said test signal plus noise that is less than said average period, detecting said function to form a direct current signal that is substantially an r.m.s. value of said varying amplitude function, and taking an inverse logarithm function of said direct current signal in order to form an output signal that is directly related to a signal-to-noise ratio in decibels.
Claim 8
Dependent Claim
50 words
The method according to claim 4 which includes an additional step of shifting the frequency of said received test signal plus noise an incremental amount prior to the step of forming said varying amplitude function, thereby to restore harmonics of said test signal into the measurement of a signal-to-noise ratio.
Claim 9
Independent Claim
187 words
A method of determining a dynamic frequency response of a communication circuit, comprising the steps of: inserting a first test signal of a single frequency into input of said communication circuit, inserting a second test signal of a single frequency into the input of said communication circuit, said second signal having substantially a lower power level than said first signal, forming a function from a signal output of the communication circuit that has an amplitude which varies in one direction in response to a period of said output signal being greater than an average period of a plurality of said output signal period and in an opposite direction in response to the period of the output signal being less than said average period, detecting said function to form a signal that is substantially an r.m.s. value of said varying amplitude function, varying the frequency of said second signal at the input of the communication circuit over the frequency range of said circuit, and observing changes in the value of said r.m.s. signal, whereby variations in frequency response of the communication circuit over its range may be detected.
Claim 10
Independent Claim
187 words
A method of determining a dynamic frequency response of a communication circuit, comprising the steps of: inserting a first test signal of a single frequency into input of said communication circuit, inserting a second test signal of a single frequency into the input of said communication circuit, said second signal having substantially a lower power level than said first signal, forming a function from a signal output of the communication circuit that has an amplitude which varies in one direction in response to a period of said output signal being greater than an average period of a plurality of said output signal period and in an opposite direction in response to the period of the output signal being less than said average period, detecting said function to form a signal that is substantially an r.m.s. value of said varying amplitude function, varying the frequency of said second signal at the input of the communication circuit over the frequency range of said circuit, and observing changes in the value of said r.m.s. signal, whereby variations in frequency response of the communication circuit over its range may be detected.
Claim 11
Dependent Claim
121 words
A communication circuit test set, comprising: means receiving an input signal plus noise for forming therefrom a function having an amplitude that varies in one direction in response to the period of said input signal plus noise being greater than an average period of a large number of cycles thereof and varying in an opposite direction in response to the period of said input signal plus noise being less than said average period, means for detecting substantially a r.m.s. value of said amplitude varying function, means receiving said r.m.s. value signal for making a logarithmic conversion thereof, and means receiving said logarithmic conversion for indicating its value, whereby said value is the sigNal-to-noise ratio of said input signal expressed in decibels.
Claim 12
Dependent Claim
121 words
A communication circuit test set, comprising: means receiving an input signal plus noise for forming therefrom a function having an amplitude that varies in one direction in response to the period of said input signal plus noise being greater than an average period of a large number of cycles thereof and varying in an opposite direction in response to the period of said input signal plus noise being less than said average period, means for detecting substantially a r.m.s. value of said amplitude varying function, means receiving said r.m.s. value signal for making a logarithmic conversion thereof, and means receiving said logarithmic conversion for indicating its value, whereby said value is the sigNal-to-noise ratio of said input signal expressed in decibels.
Claim 13
Dependent Claim
141 words
A communication circuit test set for measuring harmonic distortion of an input signal, comprising: means receiving the input signal for shifting its frequency an incremental amount, means receiving the frequency shifted input signal for forming therefrom a function having an amplitude that varies in one direction in response to the period of said frequency shifted input signal being greater than an average period of a large number of cycles thereof and varying in an opposite direction in response to the period of said frequency shifted input signal being less than said average period, means for detecting substantially a r.m.s. value of said amplitude varying function, means receiving said r.m.s. value signal for making a logarithmic conversion thereof, and means receiving said logarithmic conversion for indicating its value, whereby said value is a measure of the harmonic distortion of said input signal.
Claim 14
Dependent Claim
141 words
A communication circuit test set for measuring harmonic distortion of an input signal, comprising: means receiving the input signal for shifting its frequency an incremental amount, means receiving the frequency shifted input signal for forming therefrom a function having an amplitude that varies in one direction in response to the period of said frequency shifted input signal being greater than an average period of a large number of cycles thereof and varying in an opposite direction in response to the period of said frequency shifted input signal being less than said average period, means for detecting substantially a r.m.s. value of said amplitude varying function, means receiving said r.m.s. value signal for making a logarithmic conversion thereof, and means receiving said logarithmic conversion for indicating its value, whereby said value is a measure of the harmonic distortion of said input signal.
Claim 15
Dependent Claim
139 words
A test set according to claim 7 wherein said amplitude function forming means comprises: means responsive to an input test signal for determining a time difference between each positive one-half cycle of said input signal and an average one-half positive cycle thereof, means responsive to an input test signal for determining a time difference between each negative one-half cycle of said input signal and an average one-half negative cycle thereof, accumulating means responsive to said positive and negative time determining means for driving an output in one direction when a one-half cycle exceeds said average time duration and in an opposite direction when a one-half cycle is less than said average time duration, the amount that the output is driven being directly proportional to said time duration differences, and said average period, thereby to form said amplitude varying function.
Claim 16
Dependent Claim
25 words
A test set according to claim 7 which additionally comprises a high pass filter inserted between said varying amplitude forming means and said detecting means.
Claim 17
Dependent Claim
165 words
A communication circuit test set, comprising: means connected to an input for shifting an input signal a predetermined frequency, means for selecting either a frequency shifted input signal or the input signal from the input directly to form a selected output signal, means receiving said selected output signal for detecting the phase of said selected output, said receiving means including: means for determining a time difference between each period of said signal and an average period of a plurality of cycles of said signal, and means responsive to said time determining means for accumulating the amounts of said time differences exceeding the average period being given one sign and those differences of a period of the test signal less than said average period being given an opposite sign, thereby to form a time varying function, and means receiving said time varying function for substantially r.m.s. detecting said function, thereby to generate an output signal that is proportional to the signal-to-noise ratio of said input signal.
Claim 18
Dependent Claim
165 words
A communication circuit test set, comprising: means connected to an input for shifting an input signal a predetermined frequency, means for selecting either a frequency shifted input signal or the input signal from the input directly to form a selected output signal, means receiving said selected output signal for detecting the phase of said selected output, said receiving means including: means for determining a time difference between each period of said signal and an average period of a plurality of cycles of said signal, and means responsive to said time determining means for accumulating the amounts of said time differences exceeding the average period being given one sign and those differences of a period of the test signal less than said average period being given an opposite sign, thereby to form a time varying function, and means receiving said time varying function for substantially r.m.s. detecting said function, thereby to generate an output signal that is proportional to the signal-to-noise ratio of said input signal.
Claim 19
Dependent Claim
117 words
A test set according to claim 11 wherein said frequency shifting means includes: a first modulator connected to receive said input signal, a first single frequency oscillator connected to said first modulator to form a modulated output thereof, a single sideband filter selecting one sideband of said first modulator output, a second modulator connected to receive the single sideband output of said filter for demodulating said output, and a second single frequency oscillator having a frequency slightly different than that of said first oscillator to form a demodulated output at said second modulator, said demodulated output being the test signal shifted in frequency an amount equal to the difference in frequency of said first and second oscillators.
References Cited (Backward Citations)
US3122704A
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US3737781A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |