Patent US4447909A successfully refreshed from Google Patents.
US4447909A
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Circuit for rapid recognition of FSK signals in a radio channel
Assignee: Siemens AG
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Filing: 1982-05-17
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Granted: 1984-05-08
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Expires: 2002-05-17
Abstract
Abstract A circuit arrangement provides that false lock-in of the phase locked loop caused due to noise in a radio channel given pre-emphasis and de-emphasis is avoided and short transfer times can be obtained between the individual channels. To this end, a full-wave rectifier has a following transfer switch connected to a frequency shift keying demodulator having a phase locked loop. A high-pass filter is connected as a compensation filter in one branch and the incoming frequency shift keyed signal is directly connected to the demodulator over a second branch after it has been recognized.
Inventors
- 👤 Hans Hjorring
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:52
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L1/00; H04L1/20; H04L1/206
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
146 words
A circuit arrangement for the rapid recognition of frequency shift keying signals in a radio channel given pre-emphasis and de-emphasis, comprising: a fast frequency shift keying demodulator including an input, a data output and a lock output; said demodulator including a phase locked loop circuit; a circuit input for receiving the fast frequency keyed signals; a first branch connected to circuit input and including a high-pass filter having a structure to provide a cutoff frequency which lies above the upper cutoff frequency of the audible channel, and a second branch connected to said circuit input; and a switch including first and second inputs, and an output connected to said input of said fast frequency keying demodulator, said first input connected to said high-pass filter and said second input connected to said second branch for directly receiving said fast frequency shift keyed signals from said circuit input.
Claim 2
Dependent Claim
146 words
A circuit arrangement for the rapid recognition of frequency shift keying signals in a radio channel given pre-emphasis and de-emphasis, comprising: a fast frequency shift keying demodulator including an input, a data output and a lock output; said demodulator including a phase locked loop circuit; a circuit input for receiving the fast frequency keyed signals; a first branch connected to circuit input and including a high-pass filter having a structure to provide a cutoff frequency which lies above the upper cutoff frequency of the audible channel, and a second branch connected to said circuit input; and a switch including first and second inputs, and an output connected to said input of said fast frequency keying demodulator, said first input connected to said high-pass filter and said second input connected to said second branch for directly receiving said fast frequency shift keyed signals from said circuit input.
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) | 1987-05-08 | 1987-11-07 | 1988-05-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-08 | 1991-11-07 | 1992-05-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-08 | 1995-11-07 | 1996-05-08 | $7700.00 | Window Closed / Lapsed |