Patent US3775689A successfully refreshed from Google Patents.
US3775689A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Signal-to-noise ratio measuring system for frequency modulated communication systems
Assignee: TDK Micronas GmbH
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Filing: 1970-12-18
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Granted: 1973-11-27
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Expires: 1990-12-18
Abstract
Abstract A balanced mixer and crystal oscillator translates a baseband signal upward in frequency just below the passband of a crystal filter at the output of the mixer. The filter passes only the noise in its passband to a logarithmic amplifier-detector. The DC output of the detector is coupled to a recorder calibrated directly in signal-to-noise ratio of the translated baseband signal. Different width baseband signals (different number of FDM channels) are handled by changing the crystal of the oscillator so that the translated baseband signal remains just below the filter passband.
Inventors
- 👤 C Greenwald
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:00
CPC Classifications
H; H03; H03D; H03D7/00; H03D7/02
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
201 words
A signal-to-noise ratio measuring system comprising: a source of first signal whose signal-to-noise ratio is to be measured, said first signal including a baseband signal occupying a given band of frequencies and noise both within said given band of frequencies and outside said given band of frequencies; second means having a frequency passband in an intermediate frequency band spaced from said given band of frequencies; an adjustable heterodyne means coupled between said source and said second means to translate said baseband signal and said noise to said intermediate frequency band but spaced below said frequency passband so that said second means passes only said noise outside said translated baseband signal band of frequencies in said frequency passband, said heterodyne means enabling said second means to be employed for baseband signals having different bandwidths; third means coupled to said second means responsive to only said noise present in said frequency passband to produce a direct current voltage proportional to the logarithm of the magnitude of said noise in said frequency passband; and fourth means coupled to said third means calibrated in signalto-noise ratio to indicate the magnitude of the signal-to-noise ratio of said first signal in response to said direct current voltage.
Claim 2
Dependent Claim
201 words
A signal-to-noise ratio measuring system comprising: a source of first signal whose signal-to-noise ratio is to be measured, said first signal including a baseband signal occupying a given band of frequencies and noise both within said given band of frequencies and outside said given band of frequencies; second means having a frequency passband in an intermediate frequency band spaced from said given band of frequencies; an adjustable heterodyne means coupled between said source and said second means to translate said baseband signal and said noise to said intermediate frequency band but spaced below said frequency passband so that said second means passes only said noise outside said translated baseband signal band of frequencies in said frequency passband, said heterodyne means enabling said second means to be employed for baseband signals having different bandwidths; third means coupled to said second means responsive to only said noise present in said frequency passband to produce a direct current voltage proportional to the logarithm of the magnitude of said noise in said frequency passband; and fourth means coupled to said third means calibrated in signalto-noise ratio to indicate the magnitude of the signal-to-noise ratio of said first signal in response to said direct current voltage.
Claim 3
Dependent Claim
18 words
A system according to claim 1, wherein said second means includes a bandpass filter means having said passband.
Claim 4
Dependent Claim
18 words
A system according to claim 2, wherein said filter means includes a crystal bandpass filter having said passband.
Claim 5
Dependent Claim
32 words
A system according to claim 1, wherein said third means includes a logarithmic amplifier coupled to said second means, and a detector coupled to said amplifier to produce said direct current voltage.
Claim 6
Dependent Claim
43 words
A system according to claim 1, wherein said second means includes a crystal bandpass filter having said passband; and said third means includes a logarithmic amplifier coupled to said filter, and a detector coupled to said amplifier to produce said direct current voltage.
Claim 7
Dependent Claim
34 words
A system according to claim 1, wherein said heterodyne means includes a crystal oscillator, and a balanced mixer coupled to said source and said oscillator to provide said translated baseband signal and said noise.
Claim 8
Dependent Claim
58 words
A system according to claim 6, wherein said baseband signal includes any one of a plurality different bandwidths, and the crystal of said oscillator is selected to have a resonant frequency determined by each of said plurality of different bandwidths to provide said translated baseband signal and said noise compatible with said frequency passband of said second means.
Claim 9
Dependent Claim
18 words
A system according to claim 6, wherein said second means includes a crystal bandpass filter having said passband.
Claim 10
Dependent Claim
32 words
A system according to claim 6, wherein said third means includes a logarithmic amplifier coupled to said second means, and a detector coupled to said amplifier to produce said direct current voltage.
Claim 11
Dependent Claim
43 words
A system according to claim 6, wherein said second means includes a crystal bandpass filter having said passband; and said third means includes a logarithmic amplifier coupled to said filter, and a detector coupled to said amplifier to produce said direct current voltage.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-26 | 1977-05-28 | 1977-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-26 | 1981-05-28 | 1981-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-26 | 1985-05-28 | 1985-11-27 | $7700.00 | Window Closed / Lapsed |