US4225975A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Noise suppression circuit for use with FM receiver
Assignee: Mitsubishi Electric Corp
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Filing: 1977-09-08
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Granted: 1980-09-30
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Expires: 1997-09-08
Abstract
Abstract Two semiconductor diodes are serially interconnected across a ratio detector in the same polarity. When the detected output from the ratio detector reaches a predetermined magnitude, both diodes are conducting and the detected output is taken from the junction of the diodes. When the detected output from the ratio detector falls due to a lower received signal level, an increase in noise level is ordinarily experienced. Because the output of the ratio detector is lower, the diodes are no longer fully conductive. This causes an increase in output impedance and a corresponding reduction in noise output.
Inventors
- 👤 Yasuo Iwamoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:26
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/06; H03D3/08; H03D3/10; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/348
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
118 words
A noise suppression circuit for use with an FM receiver comprising a ratio detector, a series combination formed of a plurality of semiconductor rectifier elements interconnected with the same polarity and having a central junction, each of said semiconductor rectifier elements having nonlinear forward characteristics, said series combination being connected to said ratio detector in a forward direction relative to the detected DC output therefrom to form a DC load circuit for the latter, and means for taking an audio signal from said central junction of said series combination, whereby said semiconductor rectifier elements become conducting when said detected DC output from said ratio detector exceeds a predetermined level thereby providing an audio signal from said central junction.
Claim 2
Dependent Claim
118 words
A noise suppression circuit for use with an FM receiver comprising a ratio detector, a series combination formed of a plurality of semiconductor rectifier elements interconnected with the same polarity and having a central junction, each of said semiconductor rectifier elements having nonlinear forward characteristics, said series combination being connected to said ratio detector in a forward direction relative to the detected DC output therefrom to form a DC load circuit for the latter, and means for taking an audio signal from said central junction of said series combination, whereby said semiconductor rectifier elements become conducting when said detected DC output from said ratio detector exceeds a predetermined level thereby providing an audio signal from said central junction.
Claim 3
Dependent Claim
40 words
A noise suppression circuit for use with an FM receiver as claimed in claim 1 wherein said ratio detector includes at least a load resistance and wherein said series combination is connected across said load resistance of said ratio detector.
Claim 4
Dependent Claim
25 words
A noise suppression circuit for use with an FM receiver as claimed in claim 2 wherein said load resistance is formed of a single resistor.
Claim 5
Dependent Claim
26 words
A noise suppression circuit for use with an FM receiver as claimed in claim 1 wherein each of said semiconductor rectifier elements is a semiconductor diode.
Claim 6
Dependent Claim
29 words
A noise suppression circuit for use with an FM receiver as claimed in claim 1 wherein each of said semiconductor rectifier elements has a compensation resistor serially connected thereto.
Claim 7
Dependent Claim
39 words
A noise suppression circuit for use with an FM receiver as claimed in claim 1 wherein a de-emphasis circuit is connected to said central junction of said series combination, and said audio signal is taken through said de-emphasis circuit.
References Cited (Backward Citations)
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US3525943A
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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) | 1983-09-30 | 1984-03-31 | 1984-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-09-30 | 1988-03-31 | 1988-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-09-30 | 1992-03-31 | 1992-09-30 | $7700.00 | Window Closed / Lapsed |