US4298984A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for improving error rate on radio teletype circuits
Assignee: Department of National Defence
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Filing: 1976-10-06
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Granted: 1981-11-03
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Expires: 1996-10-06
Abstract
Abstract Existing single channel radio teletype circuits employing single frequency shift, i.e. mark/space, are prone to interference from static, impulse type noise, and selective fading. The present invention provides time diversity which improves the error rates of such circuits. A stream of binary coded data is divided into first and second identical data streams. The data in the second stream is delayed by a predetermined number of frames. Subsequently, a comparison of the data in the two streams is made and one-of-four digital signals are produced dependent on the results of the comparison. The one-of-four signals are used to produce corresponding audio tones which are transmitted. At the receiving end, the audio tones are used to produce one-of-four voltages which are processed to produce third and fourth data streams corresponding to the first data stream and the delayed second stream. The third data stream is delayed by the same amount as the second data stream was delayed during transmissions, bringing the third and fourth data streams into correspondence. The better of the two data streams is then selected for use.
Inventors
- 👤 Charles L. Baker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 11:18
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/02; H04L1/06
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
75 words
A time diversity method of transmitting binary coded data comprising dividing said data into first and second identical data streams, delaying the data in said second data stream by a predetermined number of frames, subsequently making a comparison of the data in said first and second data streams and producing one-of-four digital signals dependent on said comparison, using said one-of-four signals to produce corresponding audio tones, and transmitting a carrier modulated by said audio tones.
Claim 2
Dependent Claim
75 words
A time diversity method of transmitting binary coded data comprising dividing said data into first and second identical data streams, delaying the data in said second data stream by a predetermined number of frames, subsequently making a comparison of the data in said first and second data streams and producing one-of-four digital signals dependent on said comparison, using said one-of-four signals to produce corresponding audio tones, and transmitting a carrier modulated by said audio tones.
Claim 3
Dependent Claim
61 words
A method as claimed in claim 1 wherein said one-of-four digital signals comprise four distinct voltage levels corresponding to said comparison as follows: level 1: data "0" in both streams level 2: data "1" in both streams level 3: data "1" and "0" in first and second streams, respectively level 4: data "0" and "1" in first and second streams, respectively.
Claim 4
Dependent Claim
88 words
A method of decoding data transmitted in accordance with the method of claim 1 comprising receiving said audio tones, deriving one-of-four voltages corresponding to the received tones, producing from said one-of-four voltages third and fourth data streams corresponding to said first data stream and to the delayed second data stream respectively, delaying said third data stream by the same number of frames that said second data stream was delayed during transmission, and selecting for use the better of said fourth data stream and said delayed third data stream.
Claim 5
Dependent Claim
84 words
Time diversity apparatus for transmitting binary coded data comprising means for dividing said data into first and second identical data streams, means for delaying the data in said second data stream by a predetermined number of frames, means for subsequently making a comparison of the data in said first and second data streams and producing one-of-four digital signals dependent on said comparison, means responsive to said one-of-four signals to produce corresponding autio tones, and means for transmitting a carrier modulated by said audio tones.
Claim 6
Dependent Claim
84 words
Time diversity apparatus for transmitting binary coded data comprising means for dividing said data into first and second identical data streams, means for delaying the data in said second data stream by a predetermined number of frames, means for subsequently making a comparison of the data in said first and second data streams and producing one-of-four digital signals dependent on said comparison, means responsive to said one-of-four signals to produce corresponding autio tones, and means for transmitting a carrier modulated by said audio tones.
Claim 7
Dependent Claim
60 words
Apparatus as claimed in claim 4 wherein said one-of-four digital signals comprise four distinct voltage levels corresponding to said comparison as follows: level 1: data "0" in both streams level 2: data "1" in both streams level 3: data "1" and "0" in first and second streams, respectively level 4: data "0" and "1" in first and second streams, respectively.
Claim 8
Dependent Claim
28 words
Apparatus as claimed in claim 5 wherein said means for delaying the data in the second stream comprises a shift register controlled by a source of clock pulses.
Claim 9
Dependent Claim
96 words
Apparatus for decoding data transmitted by apparatus in accordance with claim 4 comprising means for receiving said audio tones, means for deriving one-of-four voltages corresponding to the received tones, means for producing from said one-of-four voltages third and fourth data streams corresponding to said first data stream and to the delayed second data stream respectively, means for delaying said third data stream by the same number of frames that said second data stream was delayed during transmission, and means for selecting for use the better of said fourth data stream and said delayed third data stream.
Claim 10
Dependent Claim
26 words
Apparatus as claimed in claim 7 wherein said means for delaying said third data stream comprises a shift register controlled by a source of clock pulses.
References Cited (Backward Citations)
US2548814A
Cited
US3195048A
Cited
US3354433A
Cited
US3412206A
Cited
US3560856A
Cited
US3697874A
Cited
US3508154A
Cited
US4001692A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-11-02 | 1985-05-04 | 1985-11-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-11-02 | 1989-05-04 | 1989-11-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-11-02 | 1993-05-04 | 1993-11-03 | $7700.00 | Window Closed / Lapsed |