US3596001A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency division multiplexing
Assignee: British Telecommunications Research Ltd
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Filing: 1969-10-09
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Granted: 1971-07-27
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Expires: 1989-10-09
Abstract
Abstract In a time division multiplex electrical signalling system having a main carrier modulated by a first group of subcarriers to produce signals in frequency bands of higher frequency than the main carrier and a second group of subcarriers arranged to modulate the main carrier to produce signals in frequency bands having lower frequency than that of the main carrier. Each subcarrier of the first group is modulated with respect to the main carrier by a respective information-bearing signal and each subcarrier of the second group is modulated with respect to a respective subcarrier of the first group by an informationbearing signal.
Inventors
- 👤 Adrian P Clark
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 23:00
CPC Classifications
H; H04; H04B; H04B14/00; H04B14/08
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
168 words
A method of transmitting information on a frequency division multiplex basis, the data channels being grouped in pairs comprising the steps of generating a first main carrier; generating a second main carrier having the same frequency as the first main carrier but shifted in phase by 90* with respect to the said first main carrier; generating a first subcarrier for each pair of channels, generating a second subcarrier for each pair of channels having the same frequency as the first subcarrier but shifted in phase by 90* with respect to the first subcarrier, modulating the first and second subcarriers of each pair of channels with a first information bearing signal in the first channel of said pair of channels; modulating either said first main carrier with said first modulated subcarrier or said second main carrier with said second modulated subcarrier in accordance with a second information bearing signal in the second channel of said pair of channels and combining said main carriers to form a single transmitted signal.
Claim 2
Independent Claim
168 words
A method of transmitting information on a frequency division multiplex basis, the data channels being grouped in pairs comprising the steps of generating a first main carrier; generating a second main carrier having the same frequency as the first main carrier but shifted in phase by 90* with respect to the said first main carrier; generating a first subcarrier for each pair of channels, generating a second subcarrier for each pair of channels having the same frequency as the first subcarrier but shifted in phase by 90* with respect to the first subcarrier, modulating the first and second subcarriers of each pair of channels with a first information bearing signal in the first channel of said pair of channels; modulating either said first main carrier with said first modulated subcarrier or said second main carrier with said second modulated subcarrier in accordance with a second information bearing signal in the second channel of said pair of channels and combining said main carriers to form a single transmitted signal.
Claim 3
Dependent Claim
99 words
A method of transmitting information as claimed in claim 1, comprising generating a saw-tooth waveform, applying said Saw-tooth waveform to a respective band-pass filter for each of said pairs of channels, advancing the output from each filter by one-quarter of a cycle, modulating both the nonadvanced and the advanced outputs from each filter with said respective first information bearing signal, selectively connecting either the advanced modulated output therefrom to means for amplitude modulating the main carrier or the nonadvanced modulated output therefrom to means for frequency modulating the main carrier, in accordance with said respective second information bearing signal.
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) | 1974-07-26 | 1975-01-25 | 1975-07-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-26 | 1979-01-25 | 1979-07-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-26 | 1983-01-25 | 1983-07-27 | $7700.00 | Window Closed / Lapsed |