Patent US3794928A successfully refreshed from Google Patents.
US3794928A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency shift keyed demodulator
Assignee: Collins Radio Co
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Filing: 1973-04-18
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Granted: 1974-02-26
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Expires: 1993-04-18
Abstract
Abstract A frequency shift keyed (FSK) modem (modulator and/or demodulator) utilizing a phase lock loop which modem may operate at any of several predetermined frequencies and whose output for the modulator section, is combined with a frequency shift keyed signal and the result passed through a low pass filter to provide a frequency shift keyed output. The phase lock loop also supplies signals to the receive or demodulation section. The use of a multiple frequency phase lock loop negates the requirements for a plurality of bandpass filters of different frequencies to be used with the frequency shift keyed source.
Inventors
- 👤 T Stump
- 👤 J Williford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 14:48
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
267 words
Frequency shift keyed apparatus comprising, in combination: first signal supply means for supplying first signals of first and second frequencies at a first output means indicative of data; second signal supplying means for supplying second and third signals of third and fourth frequencies at first and second outputs thereof; first and second signal combining means, each including first and second input means and output means; said signal combining means providing output signals at said output means thereof indicative in frequency of the sum and difference frequencies of signals supplied at said first and second input means thereof; irst filter means, including input means and output means, for passing fourth signals of a frequency commensurate with one of the sum and difference of said first and second frequencies with said third frequency; means connecting said first output means of each of said first and second signal supplying means to said first and seconD input means respectively of said first signal combining means for supplying said first and second signals thereto; means connecting said output means of said first signal combining means to said input means of said first filter means; means connecting said second output means of said second signal supplying means and said output means of said first filter means to said first and second input means, respectively, of said second signal combining means; and second filter means, including apparatus output means, connected to said output means of said second signal combining means for supplying signals to said apparatus output means indicative in frequency of one of the difference and summation frequencies in the signal supplied thereto.
Claim 2
Dependent Claim
267 words
Frequency shift keyed apparatus comprising, in combination: first signal supply means for supplying first signals of first and second frequencies at a first output means indicative of data; second signal supplying means for supplying second and third signals of third and fourth frequencies at first and second outputs thereof; first and second signal combining means, each including first and second input means and output means; said signal combining means providing output signals at said output means thereof indicative in frequency of the sum and difference frequencies of signals supplied at said first and second input means thereof; irst filter means, including input means and output means, for passing fourth signals of a frequency commensurate with one of the sum and difference of said first and second frequencies with said third frequency; means connecting said first output means of each of said first and second signal supplying means to said first and seconD input means respectively of said first signal combining means for supplying said first and second signals thereto; means connecting said output means of said first signal combining means to said input means of said first filter means; means connecting said second output means of said second signal supplying means and said output means of said first filter means to said first and second input means, respectively, of said second signal combining means; and second filter means, including apparatus output means, connected to said output means of said second signal combining means for supplying signals to said apparatus output means indicative in frequency of one of the difference and summation frequencies in the signal supplied thereto.
Claim 3
Dependent Claim
35 words
FSK apparatus as claimed in claim 1 wherein: said first filter means is a bandpass filter; said second filter means is a lowpass filter; and said second signal supplying means includes a phase lock loop.
Claim 4
Dependent Claim
94 words
FSK apparatus as claimed in claim 1 wherein said second signal supplying means includes: signal source means for supplying said second signals at said third frequency; frequency dividing means, connected to said signal source means for receiving said second signal therefrom and for providing output sixth signals at a frequency lower than said third frequency; and means for increasing frequency, connected between said frequency dividing means and said second output means of said second signal combining means for increasing the frequency of the signal received from said frequency dividing means to said fourth frequency.
Claim 5
Dependent Claim
32 words
FSK apparatus as claimed in claim 3 wherein said means for increasing frequency includes a phase lock loop system for altering said fourth frequency in accordance with a desired frequency output channel.
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) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |