US4528656A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radio communication system using frequency division multiplexing for transmission between a master station and a plurality of remote stations
Assignee: Harris Corp
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Filing: 1982-07-02
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Granted: 1985-07-09
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Expires: 2002-07-02
Abstract
Abstract A point-to-multipoint radio communication system includes a master station and a plurality of remote stations which communicate with the master station using frequency division multiplexing. Each remote station transmits on a separate frequency, but the respective frequencies of transmission by the remote stations are closely spaced so as to be contained within the band which is centered on a single licensed frequency. Thus, the system may operate with only a first licensed frequency for communication from the master station to the remote stations and a second licensed frequency for communications from the remote stations to the master station.
Inventors
- 👤 Douglas H. Morais
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:45
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/24; H04B7/26; H04B7/2621
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
232 words
In a system for effecting two-way radio transmission between a master station and a plurality of remote stations, each remote station comprising baseband modulation means for modulating a signal channel to produce a baseband signal at a selected frequency; a transmitter including first means for modulating said baseband signal on a carrier f c whose frequency is uniquely assigned to the respective remote station and falls within a transmission band allocated to a first licensed frequency f r and second means for transmitting said modulated baseband signal to the master station as a channel signal; a receiver including third means for receiving from said master station a multiplexed multi-channel signal modulated on a second licensed frequency f t and fourth means for downconverting said received signal to a nominal IF frequency; demodulation means for demodulating said multi-channel IF frequency signal to a multi-channel baseband signal; and demultiplexing means for locating a channel of information destined for the respective remote station in a specific section of the demodulated multi-channel baseband signal and for converting said channel located in the specific section of the baseband signal to a voice frequency channel; said first means in said transmitter including a first local oscillator for effecting modulation of said baseband signal, and said fourth means in said receiver including a second local oscillator which is independent of said first local oscillator for downconverting said received signal.
Claim 2
Dependent Claim
232 words
In a system for effecting two-way radio transmission between a master station and a plurality of remote stations, each remote station comprising baseband modulation means for modulating a signal channel to produce a baseband signal at a selected frequency; a transmitter including first means for modulating said baseband signal on a carrier f c whose frequency is uniquely assigned to the respective remote station and falls within a transmission band allocated to a first licensed frequency f r and second means for transmitting said modulated baseband signal to the master station as a channel signal; a receiver including third means for receiving from said master station a multiplexed multi-channel signal modulated on a second licensed frequency f t and fourth means for downconverting said received signal to a nominal IF frequency; demodulation means for demodulating said multi-channel IF frequency signal to a multi-channel baseband signal; and demultiplexing means for locating a channel of information destined for the respective remote station in a specific section of the demodulated multi-channel baseband signal and for converting said channel located in the specific section of the baseband signal to a voice frequency channel; said first means in said transmitter including a first local oscillator for effecting modulation of said baseband signal, and said fourth means in said receiver including a second local oscillator which is independent of said first local oscillator for downconverting said received signal.
Claim 3
Dependent Claim
102 words
A system according to claim 1, wherein the carrier frequencies f c of the plural remote stations are equally spaced within said transmission band allocated to said first licensed frequency f r , and wherein the first local oscillator in each remote station produces a carrier output f c which is equal to f c =f r -BW (N+1)/2N+BW·n/N, where BW is the authorized bandwidth of the channel centered on f r , N is the number of remote stations, and n is the position of the channel for that remote station in the transmission band in the order of increasing frequency.
Claim 4
Dependent Claim
81 words
A system according to claim 1, wherein said signal channel modulated by said baseband modulation means includes a plurality of voice frequency channels, said modulation means and said demodulation means comprising a plurality of voice frequency channel modems and multiplexing means for combining the modulated outputs of said channel modems into a baseband signal for application to said transmitter and for separating the extracted channel received from said demodulation means into channels for application to the respective voice frequency channel modems.
Claim 5
Independent Claim
86 words
A system according to claims 1 or 3, wherein said master station comprises means for receiving the plural channel signals from said remote stations; downconverting means including a local oscillator providing an output at such a frequency as to convert the received channel signals to respective intermediate frequency signals; means including a plurality of demodulators for converting the respective intermediate frequency signals to individual channel signals at a selected baseband frequency; and channel modem means for converting said channel baseband signals to outgoing voice frequency channels.
Claim 6
Dependent Claim
65 words
A system according to claim 4, wherein said channel modem means in said master station includes a plurality of modems which convert incoming voice frequency channels to channel baseband signals; means for modulating said channel baseband signals on a carrier having said second licensed frequency f t to produce said multi-channel modulated signal; and means for transmitting said multi-channel modulated signal to said remote stations.
Claim 7
Dependent Claim
56 words
A system according to claim 5, wherein said means for modulating said channel baseband signals and said downconverting means in said master station each include a separate local oscillator operating on the respective first licensed frequency f t and the second licensed frequency f r plus or minus the nominal IF frequency of said receiving means.
References Cited (Backward Citations)
US3368201A
Cited
US3495177A
Cited
US3581208A
Cited
US3670242A
Cited
US4129349A
Cited
US4117267A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-07-08 | 1989-01-07 | 1989-07-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-07-08 | 1993-01-07 | 1993-07-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-07-08 | 1997-01-07 | 1997-07-09 | $7700.00 | Window Closed / Lapsed |