Patent US3801912A successfully refreshed from Google Patents.
US3801912A
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Frequency modulation communication system and digital carrier generator and demodulator for use therein
Assignee: Racal Data Communications Inc
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Filing: 1972-03-27
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Granted: 1974-04-02
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Expires: 1992-03-27
Abstract
Abstract A data transmitter-receiver system for transmitting information over a communication link such as a telephone line is described. The information is encoded on a carrier wave at the transmitter by generating and sending the carrier at one of a plurality of selected frequencies, e.g. two, during successive modulation periods. The carrier wave at the selected frequency is generated by means of a digital wave generator which includes a pulse generator for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier wave frequency. A timing signal generator generates timing signals representative selected increments of the carrier wave period at each selected frequency. Gating means having an input connected to the pulse generator and an output is controlled by the timing signal generator for coupling a selected number of pulses to the output thereof during each of the time increments to provide an output signal having an average amplitude in the form of a recurring stair step which digitally simulates a sine or cosine wave. The gating means output signal is coupled to the telephone line via an integrator in the form of a low pass filter so that an analog sine or cosine wave at the selected frequency for each modulation period is transmitted to the receiver. A digital demodulator is provided at the receiver which includes a pulse generator for generating a train of pulses, a counter for counting the time interval of a given portion such as each onehalf of a cycle of the received carrier wave and gating means for coupling a selected number of pulses to an integrator in accordance with the time interval of each one-half cycle of the received carrier wave. The resultant d.c. signal at the integrator output has an amplitude representative of the carrier frequency during each modulation period. A level detector is provided for translating the integrator output signals into binary data.
Inventors
- 👤 R Ragsdale
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 08:59
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
168 words
In a data transmitter-receiver system for transmitting information over a communication link by encoding the information on a carrier wave during successive modulation periods at the transmitter and decoding the carrier wave at the receiver, a digital carrier wave generator at the transmitter for generating a carrier wave having a selected frequency during such modulation period which comprises: pulse generating means for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier wave frequency; timing means for generating timing signals representative of selected increments of each carrier wave period; and gating means having an input coupled to the pulse generating means and an output, the gating means being under the control of the timing means for coupling a selected number of pulses to the output thereof during each of the time increments to provide an output signal having an average amplitude which digitally simulates a sine or cosine wave at the selected frequency.
Claim 2
Dependent Claim
168 words
In a data transmitter-receiver system for transmitting information over a communication link by encoding the information on a carrier wave during successive modulation periods at the transmitter and decoding the carrier wave at the receiver, a digital carrier wave generator at the transmitter for generating a carrier wave having a selected frequency during such modulation period which comprises: pulse generating means for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier wave frequency; timing means for generating timing signals representative of selected increments of each carrier wave period; and gating means having an input coupled to the pulse generating means and an output, the gating means being under the control of the timing means for coupling a selected number of pulses to the output thereof during each of the time increments to provide an output signal having an average amplitude which digitally simulates a sine or cosine wave at the selected frequency.
Claim 3
Dependent Claim
70 words
The combination as defined in claim 1 wherein the pulse generating means includes a plurality of output circuits and is arranged to produce an individual pulse train in each output circuit so that pulses in any two output circuits are additive, and wherein the gating means selectively couples one or more output circuits of the pulse generating means to the output circuit of the gating means during successive modulation periods.
Claim 4
Dependent Claim
32 words
The combination as defined in claim 2 including a high frequency oscillator and wherein the pulse generating means and the timing means each comprise a divider coupled to the high frequency oscillator.
Claim 5
Dependent Claim
32 words
The combination as defined in claim 3 wherein the gating means includes a separate AND gate connected between each pulse generating means output circuit and the output circuit of the gating means.
Claim 6
Dependent Claim
36 words
The combination as defined in claim 2 wherein the timing means provides at least six timing signals with each timing signal being representative of a separate increment of time during each cycle of the carrier wave.
Claim 7
Dependent Claim
13 words
The combination as defined in claim 5 wherein the time increments are equal.
Claim 8
Dependent Claim
30 words
The combination as defined in claim 1 wherein the information is encoded by modulating the frequency of the carrier wave so that the selected frequency varies during successive modulation periods.
Claim 9
Dependent Claim
21 words
The combination as defined in claim 7 wherein the selected frequency varies between one of two values during successive modulAtion periods.
Claim 10
Dependent Claim
18 words
The combination as defined in claim 8 including an integrator connected to the output of the gating means.
Claim 11
Dependent Claim
76 words
The combination as defined in claim 9 wherein the gating means and the pulse generating means are arranged to selectively couple at least first, second and third separate additive pulse trains to the integrator with the first pulse train having an average amplitude of one-half of the second voltage, the second pulse train having an average amplitude of one-fourth the second voltage and the third pulse train having an average amplitude of one-eighth the second voltage.
Claim 12
Dependent Claim
40 words
The combination as defined in claim 10 wherein the gating means and the pulse generating means are arranged to couple a fourth pulse train to the integrator, the fourth pulse train having an average amplitude of one-sixteenth the second voltage.
Claim 13
Dependent Claim
27 words
The combination as defined in claim 11 wherein the gating means is further arranged to selectively couple a d.c. signal of the second level to the integrator.
Claim 14
Dependent Claim
170 words
In a data transmitter-receiver system for transmitting information over a communication link by setting the frequency of a carrier wave at one of plural values during successive modulation periods at the transmitter to represent the information and demodulating the carrier wave at the receiver to derive the transmitted information, a digital demodulator at the receiver which comprises: pulse generating means for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier frequency; counting means for counting the time interval of a selected portion of each cycle of the received carrier wave; and gating means having an input coupled to the pulse generating means and an output, the gating means being under the control of the counting means for coupling a selected number of pulses to the output thereof during each selected portion of the received carrier wave to provide an output signal having an average amplitude representative of the carrier frequency during each modulation period.
Claim 15
Dependent Claim
170 words
In a data transmitter-receiver system for transmitting information over a communication link by setting the frequency of a carrier wave at one of plural values during successive modulation periods at the transmitter to represent the information and demodulating the carrier wave at the receiver to derive the transmitted information, a digital demodulator at the receiver which comprises: pulse generating means for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier frequency; counting means for counting the time interval of a selected portion of each cycle of the received carrier wave; and gating means having an input coupled to the pulse generating means and an output, the gating means being under the control of the counting means for coupling a selected number of pulses to the output thereof during each selected portion of the received carrier wave to provide an output signal having an average amplitude representative of the carrier frequency during each modulation period.
Claim 16
Dependent Claim
77 words
The combination as defined in claim 13 wherein the pulse generating means includes a plurality of output circuits and is arranged to produce an individual pulse train in each output circuit so that the pulses in any two output circuits are additive and wherein the gating means selectively couples one or more output circuits of the pulse generating means to the output circuit of the gating means during each selected portion of the received carrier wave period.
Claim 17
Dependent Claim
32 words
The combination as defined in claim 14 including a high frequency oscillator and wherein the pulse generating means and the counting means each comprise a divider coupled to the high frequency oscillator.
Claim 18
Dependent Claim
32 words
The combination as defined in claim 15 wherein the gating means includes a separate AND gate connected between each pulse generating means output circuit and the output circuit of the gating means.
Claim 19
Dependent Claim
24 words
The combination as defined in claim 14 wherein the counting means measures the time interval of each half cycle of the received carrier wave.
Claim 20
Dependent Claim
71 words
The combination as defined in claim 17 including integrating means connected to the output of the gating means and an amplitude level detector connected to the integrating means for providing an output signal of one level when the amplitude of the signal from the integrator is above a predetermined value and an output signal of another level when the amplitude of the signal from the integrator is below said predetermined value.
Claim 21
Dependent Claim
77 words
The combination as defined in claim 18 wherein the pulse generating means and the gating means are arranged to selectively couple at least first, second and third separate additive pulse trains to the integrating means with the first pulse train having an average amplitude of one-half of the second voltage, the second pulse train having an average amplitude of one-fourth the second voltage and the third pulse train having an averAge amplitude of one-eighth the second voltage.
Claim 22
Dependent Claim
41 words
The combination as defined in claim 19 wherein the pulse generating means and the gating means are arranged to couple a fourth pulse train to the integrating means, the fourth pulse train having an average amplitude of one-sixteenth the second voltage.
Claim 23
Dependent Claim
197 words
In a frequency shift keying data transmitter-receiver system for transmitting information over a communication link by shifting the frequency of a carrier wave beetween one of two values during successive modulation periods and demodulating the carrier wave at the receiver, a transmitter which comprises: a pulse generator for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier wave frequency; timing signal generating means responsive to the data to be transmitted for generating timing signals corresponding to a selected number of increments of the carrier wave period at the selected frequency for each modulation period; an integrator having an input and an output; gating means connected between the pulse generating means and the integrator input and being responsive to the timing signal generating means for coupling a selected number of pulses to the integrator input during each of the time increments so that the average amplitude of the pulses coupled to the integrator vary in a stair step wave between the first and second voltage levels to digitally simulate a sine or cosine wave at the selected frequency for each modulation period.
Claim 24
Dependent Claim
197 words
In a frequency shift keying data transmitter-receiver system for transmitting information over a communication link by shifting the frequency of a carrier wave beetween one of two values during successive modulation periods and demodulating the carrier wave at the receiver, a transmitter which comprises: a pulse generator for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier wave frequency; timing signal generating means responsive to the data to be transmitted for generating timing signals corresponding to a selected number of increments of the carrier wave period at the selected frequency for each modulation period; an integrator having an input and an output; gating means connected between the pulse generating means and the integrator input and being responsive to the timing signal generating means for coupling a selected number of pulses to the integrator input during each of the time increments so that the average amplitude of the pulses coupled to the integrator vary in a stair step wave between the first and second voltage levels to digitally simulate a sine or cosine wave at the selected frequency for each modulation period.
Claim 25
Dependent Claim
68 words
The combination as defined in claim 21 wherein the gating means and the pulse generator are arranged to selectively couple at least first, second and third additive pulse trains to the integrator input with the first pulse train having an average amplitude of one-half the second voltage lvel, the second and third pulse trains having an average amplitude of one-half and one-fourth, respectively, of the first pulse train.
Claim 26
Dependent Claim
43 words
The combination as defined in claim 22 wherein the gating means and the pulse generator are further arranged to selectively couple a fourth pulse train to the integrator having an average amplitude of one-eighth of the average amplitude of the first pulse train.
Claim 27
Dependent Claim
28 words
The combination as defined in claim 23 wherein the gating means is further arranged to selectively couple a d.c. signal of the second level to the integrating input.
Claim 28
Dependent Claim
26 words
The combination as defined in claim 23 wherein the timing signal generator generates timing signals corresponding to at least six increments of the carrier wave period.
Claim 29
Dependent Claim
18 words
The combination as defined in claim 25 wherein the number of increments of the carrier wave is twelve.
Claim 30
Dependent Claim
121 words
The combination as defined in claim 21 including a receiver which comprises: a pulse generator means for generating a series of pulses which vary between first and second voltage levels at a pulse repetition rate which is high compared to the carrier frequency; a counter for counting the time interval of each one-half cycle of the received carrier wave; and gating means having an input coupled to the pulse generator and an output, the gating means being under the control of the counter for coupling a selected number of pulses to the output thereof during each one-half cycle of the received carrier wave to provide an output signal having an average amplitude representative of the carrier frequency during each modulation period.
Claim 31
Dependent Claim
76 words
The combination as defined in claim 27 including an integrator connected to the gating means output and a voltage level detector connected to the integrator, the level detector being arranged to produce a binary signal of one value when the amplitude of the output signal from the integrator is above a predetermined level and to produce a binary signal of a second value when the amplitude of the integrator output signal is below said predetermined value.
Claim 32
Dependent Claim
68 words
The combination as defined in claim 28 wherein the gating means and tHe pulse generator are arranged to selectively couple at least first, second and third additive pulse trains to the integrator input with the first pulse train having an average amplitude of one-half the second voltage leve, the second and third pulse trains having an average amplitude of one-half and one-fourth, respectively, of the first pulse train.
Claim 33
Dependent Claim
177 words
In a digitally controlled function generator for generating a digitally simulated geometric function, the combination which comprises: a high frequency oscillator; pulse generating means coupled to the oscillator for producing an individual pulse train of substantially constant maximum and minimum amplitude in each of a plurality of output circuits so that the pulse trains in two or more output circuits may be added and integrated to provide a d.c. signal of greater amplitude than the integrated signal from one of said output circuits; integrating means having an input and an output circuit; timing signal generating means for generating timing signals representing selected sampling intervals of the geometric function; and gating means coupled between the input circuit of the integrating means and the output circuits of the pulse generating means, the gating means being responsive to the timing signals for connecting selected output circuits of the pulse generating means to the integrating means during successive sampling time intervals to provide successive d.c. level signals in the output circuit of the integrating means to digitally simulate the geometric function.
Claim 34
Dependent Claim
177 words
In a digitally controlled function generator for generating a digitally simulated geometric function, the combination which comprises: a high frequency oscillator; pulse generating means coupled to the oscillator for producing an individual pulse train of substantially constant maximum and minimum amplitude in each of a plurality of output circuits so that the pulse trains in two or more output circuits may be added and integrated to provide a d.c. signal of greater amplitude than the integrated signal from one of said output circuits; integrating means having an input and an output circuit; timing signal generating means for generating timing signals representing selected sampling intervals of the geometric function; and gating means coupled between the input circuit of the integrating means and the output circuits of the pulse generating means, the gating means being responsive to the timing signals for connecting selected output circuits of the pulse generating means to the integrating means during successive sampling time intervals to provide successive d.c. level signals in the output circuit of the integrating means to digitally simulate the geometric function.
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) | 1977-04-01 | 1977-10-01 | 1978-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-01 | 1981-10-01 | 1982-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-01 | 1985-10-01 | 1986-04-02 | $7700.00 | Window Closed / Lapsed |