US3810019A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multifrequency communication system for fading channels
Assignee: Unisys Corp
•
Filing: 1972-09-25
•
Granted: 1974-05-07
•
Expires: 1992-09-25
Abstract
Abstract A communication system particularly for underwater communication includes a transmitter and a receiver. An oscillator in the transmitter generates a plurality of signals each having a unique frequency. A network selects predetermined combinations of signals from this plurality, each selected combination defining a data symbol to be transmitted. The assignment of the frequency groups with respect to the data symbols to be transmitted is achieved via a Hadamard matrix. During each data symbol transmission interval a gate selects the combination of frequency signals corresponding to the symbol to be transmitted. The signals in the combination are added and transmitted by a transducer. The receiver includes a bank of filters each tuned to one of the plurality of frequency signals generated in the oscillator bank. The outputs of the filters are envelope detected and applied to a frequency code selector. In each data symbol transmission interval, the frequency code selector combines the detected outputs from the filter bank in accordance with the Hadamard transformation matrix to provide a plurality of groups of signals each corresponding to a symbol in the system symbol repertoire. Each group of signals are summed and the resulting signals applied to a decision circuit that selects the maximum therefrom. The output of the decision circuit which is representative of the transmitted symbol is applied to a suitable readout.
Inventors
- 👤 C Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 02:42
CPC Classifications
H; H04; H04B; H04B11/00; H04L; H04L27/00; H04L27/26; H04L27/30
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
194 words
A system for communicating data items comprising transmitter means, receiver means, transmitting and receiving transducer means coupled to said transmitter and receiver means respectively, said transmitter means comprising oscillator bank means for providing a plurality of signals, each signal having a unique frequency, transmitter switching means for selecting groups of signals from said plurality of signals, said groups representative of said data items respectively, said groups of signals being associated with said respective data items in accordance with a substantially Hadamard matrix, at least two said groups including the same signal, means for energizing said transmitting transducer means with a signal corresponding to the combined signals in a selected group, said receiver means comprising filter bank means responsive to said receiving transducer means for filtering the received signal in accordance with each of the frequencies provided by said oscillator bank means and providing filtered signals in accordance therewith, receiver switching means for selecting groups of said filtered signals in accordance with said Hadamard matrix, means for combining each selected group of filtered signals, and means for comparing the combined groups of filtered signals with respect to each other for determining the data item transmitted.
Claim 2
Independent Claim
194 words
A system for communicating data items comprising transmitter means, receiver means, transmitting and receiving transducer means coupled to said transmitter and receiver means respectively, said transmitter means comprising oscillator bank means for providing a plurality of signals, each signal having a unique frequency, transmitter switching means for selecting groups of signals from said plurality of signals, said groups representative of said data items respectively, said groups of signals being associated with said respective data items in accordance with a substantially Hadamard matrix, at least two said groups including the same signal, means for energizing said transmitting transducer means with a signal corresponding to the combined signals in a selected group, said receiver means comprising filter bank means responsive to said receiving transducer means for filtering the received signal in accordance with each of the frequencies provided by said oscillator bank means and providing filtered signals in accordance therewith, receiver switching means for selecting groups of said filtered signals in accordance with said Hadamard matrix, means for combining each selected group of filtered signals, and means for comparing the combined groups of filtered signals with respect to each other for determining the data item transmitted.
Claim 3
Independent Claim
192 words
A system for communicating data items comprising transmitter means, receiver means, transmitting and receiving transducer means coupled to said transmitter and receiver means respectively, said transmitter means comprising oscillator bank means for providing a plurality of signals, each signal having a unique frequency, transmitter switching means for selecting groups of signals from said plurality of signals, said groups representative of said data items respectively, said groups of signals being associated with said respective data items in accordance with a matrix equivalent to a substantially Hadamard matrix in normal form, means for energizing said transmitting transducer means with a signal corresponding to the combined signals in a selected group, said receiver means comprising filter bank means responsive to said receiving transducer means for filtering the received signal in accordance with each of the frequencies provided by said oscillator bank means and providing filtered signals in accordance therewith, receiver switching means for selecting groups of said filtered signals in accordance with said equivalent matrix, means for combining each selected group of filtered signals, and means for comparing the combined groups of filtered signals with respect to each other for determining the data item transmitted.
Claim 4
Independent Claim
192 words
A system for communicating data items comprising transmitter means, receiver means, transmitting and receiving transducer means coupled to said transmitter and receiver means respectively, said transmitter means comprising oscillator bank means for providing a plurality of signals, each signal having a unique frequency, transmitter switching means for selecting groups of signals from said plurality of signals, said groups representative of said data items respectively, said groups of signals being associated with said respective data items in accordance with a matrix equivalent to a substantially Hadamard matrix in normal form, means for energizing said transmitting transducer means with a signal corresponding to the combined signals in a selected group, said receiver means comprising filter bank means responsive to said receiving transducer means for filtering the received signal in accordance with each of the frequencies provided by said oscillator bank means and providing filtered signals in accordance therewith, receiver switching means for selecting groups of said filtered signals in accordance with said equivalent matrix, means for combining each selected group of filtered signals, and means for comparing the combined groups of filtered signals with respect to each other for determining the data item transmitted.
Claim 5
Independent Claim
195 words
A system for communicating data items comprising transmitter means, receiver means, transmitting and receiving transducer means coupled to said transmitter and receiver means respectively, said transmitter means comprising oscillator bank means for providing a plurality of signals, each signal having a unique frequency, transmitter switching means for selecting groups of signals from said plurality of signals, said groups representative of said data items respectively, said groups of signals being associated with said respective data items by a modulation matrix derived from a matrix equivalent to a substantially Hadamard matrix in normal form, means for energizing said transmitting transducer means with a signal corresponding to the combined signals in a selected group, said receiver means comprising filter bank means responsive to said receiving transducer meAns for filtering the received signal in accordance with each of the frequencies provided by said oscillator bank means and providing filtered signals in accordance therewith, receiver switching means for selecting groups of said filtered signals in accordance with said modulation matrix, means for combining each selected group of filtered signals, and means for comparing the combined groups of filtered signals with respect to each other for determining the data item transmitted.
Claim 6
Independent Claim
195 words
A system for communicating data items comprising transmitter means, receiver means, transmitting and receiving transducer means coupled to said transmitter and receiver means respectively, said transmitter means comprising oscillator bank means for providing a plurality of signals, each signal having a unique frequency, transmitter switching means for selecting groups of signals from said plurality of signals, said groups representative of said data items respectively, said groups of signals being associated with said respective data items by a modulation matrix derived from a matrix equivalent to a substantially Hadamard matrix in normal form, means for energizing said transmitting transducer means with a signal corresponding to the combined signals in a selected group, said receiver means comprising filter bank means responsive to said receiving transducer meAns for filtering the received signal in accordance with each of the frequencies provided by said oscillator bank means and providing filtered signals in accordance therewith, receiver switching means for selecting groups of said filtered signals in accordance with said modulation matrix, means for combining each selected group of filtered signals, and means for comparing the combined groups of filtered signals with respect to each other for determining the data item transmitted.
Claim 7
Dependent Claim
42 words
The system of claim 3 in which said modulation matrix is derived from said Hadamard matrix by deleting the one row of said matrix that has all elements the same, and appending to the rows of the resulting matrix the complements thereof.
Claim 8
Dependent Claim
36 words
The system of claim 2 in which said means for energizing includes means for selecting said group in accordance with said data item to be transmitted, and means for summing the signals in said selected group.
Claim 9
Dependent Claim
14 words
The system of claim 2 in which said means for combining comprises summing means.
Claim 10
Dependent Claim
21 words
The system of claim 2 in which said means for comparing comprises means for selecting the maximum of said combined groups.
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) | 1977-05-06 | 1977-11-05 | 1978-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-06 | 1981-11-05 | 1982-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-06 | 1985-11-05 | 1986-05-07 | $7700.00 | Window Closed / Lapsed |