US3988540A
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Integrated circuit modem with a memory storage device for generating a modulated carrier signal
Assignee: Racal Data Communications Inc
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Filing: 1974-12-10
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Granted: 1976-10-26
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Expires: 1994-12-10
Abstract
Abstract An apparatus capable of transmitting digital data at high data rates over a communication link is disclosed. A carrier signal is modulated by serial groups of digital data signals to be transmitted during a plurality of successively appearing modulation periods. The data-modulated carrier is represented by a unique group of digital signals stored in a memory. The memory upon command, reads out a predetermined sequence of digital signals with each predetermined sequence representing the signal shape of a digital data modulated carrier signal which appears as though it has been passed through a narrow band limited linear phase network. The memory stores a predetermined number of such sequences of digital signals.
Inventors
- 👤 John B. Scott
- 👤 Sang Y. Whang
- 👤 Robert G. Ragsdale
- 👤 Ran-Fun Chiu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:27
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/18; H04L27/20; H04L27/2032; H04L27/2035
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
247 words
In a continuous carrier communication system wherein a carrier signal is phase-modulated according to binary data, apparatus for generating said phase modulated carrier signal, comprising: memory means for storing in each of M addressable locations (M being an integer), N words, said words being divided into P sectors (both N and P being integers), the N words in each of said M addressable locations being an encoded representation of a unique phase modulated carrier signal that has been passed through a linear phase narrow bandwidth filter having a passband width defined as 1/T Hz with a center frequency of f o , where T is the modulation period and f o is the carrier signal frequency, each of said P sectors being an encoded representation of one modulation period T; means responsive to said binary data, for addressing the M locations in said storing means according to a sequence determined by the binary data; means for reading from said memory means, each time one of said M addressable locations is addressed, one of said N words from its respective sector P; each sector of said P sectors in their respective M locations in memory being read out so as to be offset from the sector in another of said M addressable locations by one sector; and means for adding the N words read from their respective sectors during one addressing sequence for the M locations in said storing means, thereby generating a phase modulated, filtered carrier signal.
Claim 2
Dependent Claim
247 words
In a continuous carrier communication system wherein a carrier signal is phase-modulated according to binary data, apparatus for generating said phase modulated carrier signal, comprising: memory means for storing in each of M addressable locations (M being an integer), N words, said words being divided into P sectors (both N and P being integers), the N words in each of said M addressable locations being an encoded representation of a unique phase modulated carrier signal that has been passed through a linear phase narrow bandwidth filter having a passband width defined as 1/T Hz with a center frequency of f o , where T is the modulation period and f o is the carrier signal frequency, each of said P sectors being an encoded representation of one modulation period T; means responsive to said binary data, for addressing the M locations in said storing means according to a sequence determined by the binary data; means for reading from said memory means, each time one of said M addressable locations is addressed, one of said N words from its respective sector P; each sector of said P sectors in their respective M locations in memory being read out so as to be offset from the sector in another of said M addressable locations by one sector; and means for adding the N words read from their respective sectors during one addressing sequence for the M locations in said storing means, thereby generating a phase modulated, filtered carrier signal.
Claim 3
Dependent Claim
94 words
The apparatus in accordance with claim 1 wherein: said phase modulated carrier signal has a signal spectrum I(t) extending over a plurality of modulation periods, said spectrum defined by the formula of; I(t) = [pulse response] ×[amplitude] × [sin (ωt + θ)] where: a. "pulse response" is a step function input of one modulation period duration, b. "amplitude" is any preselected value, c. ω is related to the carrier frequency, f o , and d. θ is any selected predetermined angle at least partially identifying a unique bit arrangement in a given multi-bit grouping.
Claim 4
Dependent Claim
32 words
The apparatus of claim 1 wherein the relationship between the addressable locations M, the words N in each addressable location, and the sectors P in each addressable location is N/P = M.
Claim 5
Dependent Claim
16 words
The apparatus of claim 3 wherein M = 4, N = 48, and P = 12.
Claim 6
Dependent Claim
23 words
The apparatus of claim 1 wherein said modulation period T is equal to 1/2 cycles of the carrier signal frequency f o .
Claim 7
Dependent Claim
28 words
The apparatus of claim 5 further comprising means for compensating for the 180° phase shift inherent in the carrier signal because of the 11/2 cycle modulation period T.
Claim 8
Dependent Claim
62 words
The apparatus in accordance with claim 1 and further comprising: means for grouping data into equal multi-bit groups; and encoding means connected to said grouping means and responsive to said multi-bit groups for emitting address characters to said addressing means, said characters determining a sequence indicative of the unique identity of the binary bits of the group encoded by said encoding means.
Claim 9
Dependent Claim
35 words
The apparatus in accordance with claim 7 wherein: each said multi-bit data group is represented by at least a phase difference in said carrier signal from one modulation period to a successive adjacent modulation period
Claim 10
Dependent Claim
69 words
The apparatus in accordance with claim 8 wherein: said difference in phase is assigned predetermined equal angle amounts to represent each unique binary bit possibility in said multi-bit groups and further comprising; means associated with said encoding means for emitting a character in each successive modulation period which is indicative of said unique bits represented therein by said predetermined phase difference amount from one modulation period to the next.
Claim 11
Dependent Claim
86 words
The apparatus in accordance with claim 9 wherein said encoding means, comprises: a read only memory for emitting said address characters as multi-bit binary characters uniquely associated with the bit possibilities in said multi-bit groups, and; said means for emitting a character comprises; a binary adder connected to said read only memory; and a binary accumulator connected to said binary adder to accumulate and feed back thereto each preceding address character as a new character is read from said read only memory to said binary adder.
Claim 12
Dependent Claim
70 words
The apparatus in accordance with claim 9 wherein: the phase angle amounts stored in said memory storage as a plurality of sequences of unique binary bits represent are multiples of 45° phase angles; and said apparatus is further characterized in that the binary bits having the same value but opposite polarities to represent said phase angle are; a. 45° and 225° b. 90° and 270°, and c. 135° and 315°.
Claim 13
Dependent Claim
40 words
The apparatus in accordance with claim 11 wherein: said binary bits are in the form of multi-bit digital words in a binary one's complement to exhibit different polarities of the signal represented thereby with respect to a selected reference value.
Claim 14
Dependent Claim
95 words
The apparatus in accordance with claim 7 wherein: said phase modulated carrier signal has a signal specturm I(t) extending over a plurality of modulation periods, said spectrum defined by the formula of; I(t) = [pulse response] × [amplitude] × [sin (ωt + θ)] where: a. "pulse response" is a step function input of one modulation period duration, b. "amplitude" is any preselected value, c. ω is related to the carrier frequency, f o , and d. θ is any selected predetermined angle at least partially identifying a unique bit arrangement in a given multi-bit grouping.
Claim 15
Dependent Claim
56 words
The apparatus in accordance with claim 13 wherein: the plurality of successive modulation periods occupied by each signal spectrum is a frame consisting of at least four modulation periods per frame; and further comprising timing control means for offsetting in time each frame of four successive frames by one modulation period relative to a preceding frame.
Claim 16
Dependent Claim
38 words
The apparatus in accordance with claim 14 wherein: each signal spectrum during a frame has a particularly unique shape that represents the predetermined level modulated on said carrier and identifying the unique bits of said equal multi-bit grouping.
Claim 17
Dependent Claim
57 words
The apparatus in accordance with claim 15 wherein: the number of levels is four; said multi-bit grouping means group serial incoming data into pairs of binary bits per group; and each signal spectrum frame associated with one of the four binary possibilities represents a predetermined absolute phase amount that is a multiple of a 90° phase angle.
Claim 18
Dependent Claim
76 words
The apparatus in accordance with claim 16 wherein: each one of said signal spectrums has an amplitude shape which includes low-valued constants in the first and last modulation periods of each frame as compared with relatively high-values constants in the other modulation periods of said frame; and further comprising means reading said low-valued constants from said memory at the beginning and end of every data transmission sequence for avoiding abrupt signal changes on said communication link.
Claim 19
Dependent Claim
80 words
The apparatus in accordance with claim 17 wherein said constant reading means comprises: means for reading said low-valued constants from said storage means during a first modulation period of a first frame; and means inhibiting reading of any constants from said memory storage during the offset modulation periods of the other frames of said plurality of frames; said apparatus further characterized in that said alternate reading and inhibiting means are operative only during the initiation of a data transmission sequence.
Claim 20
Dependent Claim
60 words
The apparatus in accordance with claim 17 and further comprising: means operative during the termination of a data transmission sequence for alternately reading and inhibiting reading of constants from said storage means as said offset frames appear in time after the last modulation period terminates for the first frame which completes its last signal spectrum of the data transmission sequence.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-10-26 | 1980-04-26 | 1980-10-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-10-26 | 1984-04-26 | 1984-10-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-10-26 | 1988-04-26 | 1988-10-26 | $7700.00 | Window Closed / Lapsed |