Patent US1597331A successfully refreshed from Google Patents.
US3676684A
Expired / Lapsed
US
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Frequency-division multiplex communication system
Assignee: AT&T Inc
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Filing: 1970-09-23
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Granted: 1972-07-11
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Expires: 1990-09-23
Abstract
Abstract A frequency-division multiplex communication system is described wherein the multiplexer comprises a plurality of branches, each one of which selectively isolates and modulates one of a plurality of input carrier signals. The modulated signals are either reflected to rejoin the unmodulated carriers or they are separated and combined in a separate output circuit. At the receiver a demultiplexer selectively isolates the several modulated carriers by means of a network similar to the multiplexer, and demodulates them in turn. A repeater, using a demultiplexer-multiplexer pair is also shown.
Inventors
- 👤 Owen Edward De Lange
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:35
CPC Classifications
H; H04; H04J; H04J1/00; H04J1/02; H04J1/10; H04J1/06; H04J1/12
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
307 words
A frequency-division multiplex communication system including: a transmitter; a receiver; and a transmission path connecting said transmitter to said receiver; characterized in that said transmitter includes a multiplexer having a plurality of branches, each adapted to modulate one of a plurality of carrier signals and each comprising, in cascade: a circulator for coupling incident wave energy between a first and a second port, and for coupling reflected wave energy between said second and a third port; a filter, coupled to said second port and tuned to pass one of said carriers and to reflect all the other of said carriers; a modulator for modulating the carrier passed by said filter; means for reflecting said modulated carrier back through said filter to said circulator along with the other Of said carriers; means for coupling said reflected carriers derived from the third port of said circulator into the next adjacent branch; and means at the output of the last of said branches for directing said carriers along said transmission path; and further characterized in that said receiver includes a demultiplexer having a plurality of branches, each adapted to separate and detect a different one of a plurality of modulated carriers; each of the first N-1 branches of said demultiplexer comprising, in cascade: a circulator for coupling incident wave energy between a first and a second port, and for coupling reflected wave energy between said second and a third port; a filter, coupled to said second port, tuned to pass one of said modulated carriers; the last branch of said demultiplexer including a filter, tuned to pass the Nth modulated carrier; means coupled to each of said filters for demodulating said passed carrier; and means at the input end of said branches for redirecting the reflected carriers derived from the third port of said circulator into the next adjacent branch.
Claim 2
Dependent Claim
307 words
A frequency-division multiplex communication system including: a transmitter; a receiver; and a transmission path connecting said transmitter to said receiver; characterized in that said transmitter includes a multiplexer having a plurality of branches, each adapted to modulate one of a plurality of carrier signals and each comprising, in cascade: a circulator for coupling incident wave energy between a first and a second port, and for coupling reflected wave energy between said second and a third port; a filter, coupled to said second port and tuned to pass one of said carriers and to reflect all the other of said carriers; a modulator for modulating the carrier passed by said filter; means for reflecting said modulated carrier back through said filter to said circulator along with the other Of said carriers; means for coupling said reflected carriers derived from the third port of said circulator into the next adjacent branch; and means at the output of the last of said branches for directing said carriers along said transmission path; and further characterized in that said receiver includes a demultiplexer having a plurality of branches, each adapted to separate and detect a different one of a plurality of modulated carriers; each of the first N-1 branches of said demultiplexer comprising, in cascade: a circulator for coupling incident wave energy between a first and a second port, and for coupling reflected wave energy between said second and a third port; a filter, coupled to said second port, tuned to pass one of said modulated carriers; the last branch of said demultiplexer including a filter, tuned to pass the Nth modulated carrier; means coupled to each of said filters for demodulating said passed carrier; and means at the input end of said branches for redirecting the reflected carriers derived from the third port of said circulator into the next adjacent branch.
Claim 3
Dependent Claim
122 words
In an optical communication system, a frequency-division multiplexer comprising: a plurality of branches, each adapted to modulate one of a plurality of carrier signals; each of said branches including in cascade: a polarization discriminator; a quarter-wave plate; a filter tuned to pass one of said carriers and to reflect all the other of said carriers; a modulator for modulating the carrier passed by said filter; means for reflecting said modulated carrier back through said modulator, filter and quarter-wave plate and into said polarization discriminator, along with the other of said carriers; means for coupling said reflected carrier signals into the next adjacent branch; and means at the output of the last of said branches for directing said carriers along a common wavepath.
Claim 4
Dependent Claim
122 words
In an optical communication system, a frequency-division multiplexer comprising: a plurality of branches, each adapted to modulate one of a plurality of carrier signals; each of said branches including in cascade: a polarization discriminator; a quarter-wave plate; a filter tuned to pass one of said carriers and to reflect all the other of said carriers; a modulator for modulating the carrier passed by said filter; means for reflecting said modulated carrier back through said modulator, filter and quarter-wave plate and into said polarization discriminator, along with the other of said carriers; means for coupling said reflected carrier signals into the next adjacent branch; and means at the output of the last of said branches for directing said carriers along a common wavepath.
Claim 5
Dependent Claim
13 words
The multiplexer according to claim 2 wherein said reflecting means is a mirror.
Claim 6
Dependent Claim
30 words
The multiplexer according to claim 2 wherein said reflecting means is a band-reject filter tuned to reflect said modulated carrier and to transmit said other carriers out of said multiplexer.
Claim 7
Dependent Claim
13 words
The multiplexer according to claim 2 wherein said discriminator is a nicol prism.
Claim 8
Dependent Claim
11 words
The multiplexer according to claim 2 including a multifrequency optical source.
Claim 9
Dependent Claim
12 words
The multiplexer according to claim 6 wherein said source is a laser.
Claim 10
Dependent Claim
124 words
In an optical communication system, a frequency-division multiplexer comprising: a plurality of branches, each adapted to modulate one of a plurality of carrier signals; each of said branches, including in cascade: a polarization selective member; a first quarter-wave plate; a first filter tuned to pass one of said carriers and to reflect all the other of said carriers; a modulator for modulating the carrier passed by said filter; a second filter; a second quarter-wave plate; means at the output ends of said branches for combining along a common wavepath the signals passed by the second filters; and means at the input ends of said branches for redirecting the carrier signals reflected by the first filter in the respective branches into the next adjacent branch.
Claim 11
Dependent Claim
124 words
In an optical communication system, a frequency-division multiplexer comprising: a plurality of branches, each adapted to modulate one of a plurality of carrier signals; each of said branches, including in cascade: a polarization selective member; a first quarter-wave plate; a first filter tuned to pass one of said carriers and to reflect all the other of said carriers; a modulator for modulating the carrier passed by said filter; a second filter; a second quarter-wave plate; means at the output ends of said branches for combining along a common wavepath the signals passed by the second filters; and means at the input ends of said branches for redirecting the carrier signals reflected by the first filter in the respective branches into the next adjacent branch.
Claim 12
Dependent Claim
14 words
The multiplexer according to claim 8 including an amplifier in each of said branches.
Claim 13
Dependent Claim
25 words
The multiplexer according to claim 9 wherein the second filter in each of said branches is tuned to pass the modulated carrier and its sidebands.
Claim 14
Dependent Claim
32 words
The multiplexer according to claim 9 wherein the second filter in each of said branches is tuned to pass only a single sideband, and to reflect the carrier and its other sideband.
Claim 15
Dependent Claim
102 words
In an optical communication system, a frequency-division demultiplexer for separating a plurality of modulated carriers comprising: a plurality of branches, each of the first N-1 branches including in cascade: a polarization discrimInator; a quarter-wave plate; a filter, tuned to pass one of said modulated carriers and to reflect all the other of said modulated carriers; the last branch of said demultiplexer including only a filter tuned to pass the Nth carrier; means coupled to each of said filters for demodulating said passed carrier; and means at the input end of said branches for redirecting the reflected carriers into the next adjacent branch.
Claim 16
Dependent Claim
102 words
In an optical communication system, a frequency-division demultiplexer for separating a plurality of modulated carriers comprising: a plurality of branches, each of the first N-1 branches including in cascade: a polarization discrimInator; a quarter-wave plate; a filter, tuned to pass one of said modulated carriers and to reflect all the other of said modulated carriers; the last branch of said demultiplexer including only a filter tuned to pass the Nth carrier; means coupled to each of said filters for demodulating said passed carrier; and means at the input end of said branches for redirecting the reflected carriers into the next adjacent branch.
Claim 17
Dependent Claim
13 words
The demultiplexer according to claim 12 wherein said demodulating means is a detector.
Claim 18
Dependent Claim
50 words
The demultiplexer according to claim 12 wherein said demodulating means comprises: a frequency converter; means for coupling a local oscillator signal to said frequency converter to produce an intermediate frequency signal; means for filtering said intermediate frequency signal; and means for detecting the modulation impressed upon said intermediate frequency signal.
Claim 19
Dependent Claim
23 words
The demultiplexer according to claim 14 wherein the local oscillator signals coupled to said converters are derived from a common, multifrequency signal source.
References Cited (Backward Citations)
US3501223A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-11 | 1976-01-10 | 1976-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-11 | 1980-01-10 | 1980-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-11 | 1984-01-10 | 1984-07-11 | $7700.00 | Window Closed / Lapsed |