US3699447A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Wideband frequency modulation communications system
Assignee: International Business Machines Corp
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Filing: 1971-01-05
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Granted: 1972-10-17
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Expires: 1991-01-05
Abstract
Abstract A duobinary data input having a first signal spectrum in a relatively low frequency range is fed to a mixer and bandpass filter. The mixer and bandpass filter frequency translates the first signal spectrum to obtain a second signal spectrum separated upwardly in frequency range from the first spectrum. The signal of the second spectrum frequency modulates a carrier wave having a frequency that is near to the upper frequency limit of the second spectrum, so that only a single pair of sidebands is produced by each modulating frequency component. The frequency modulated signal is then passed through a limiter, a divider, and a low pass vestigial sideband filter, respectively, so that the frequency modulated carrier is frequency translated to a third signal spectrum which occupies a bandwidth approximating the bandwidth of the first band of frequencies. This frequency translated FM carrier wave contains a constant carrier wave component and lower frequency sidebands, arranged compactly in a relatively narrow bandwidth. The output of the low pass vestigial sideband filter may be recorded on a recording medium or transmitted in a band limited channel, so that a carrier usable for clocking the duobinary encoded data is continuously present.
Inventors
- 👤 William Thomas Frost
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 02:45
CPC Classifications
H; H04; H04L; H04L27/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
166 words
A method for transmitting clocked duobinary encoded information by frequency modulation of a carrier wave, said method comprising: frequency translating and filtering a first frequency spectrum containing said clocked duobinary encoded information, to provide a second frequency spectrum separated from said first frequency spectrum; frequency modulating the carrier wave with said second frequency spectrum; the frequency of said carrier wave being spectrally near to the upper frequency limit of said second frequency spectrum and frequency modulated so that the modulation index is always less than 0.4 and only a single pair of sidebands are produced by each modulating frequency component; frequency translating and filtering the frequency modulated carrier wave so that it has a bandwidth approximating the bandwidth of said first frequency spectrum, said frequency translated and filtered frequency modulated carrier wave containing a constant carrier wave component and lower frequency sidebands, with the carrier component providing a continuously present clocking signal; and transmitting said frequency translated and filtered FM carrier wave to an output channel.
Claim 2
Independent Claim
166 words
A method for transmitting clocked duobinary encoded information by frequency modulation of a carrier wave, said method comprising: frequency translating and filtering a first frequency spectrum containing said clocked duobinary encoded information, to provide a second frequency spectrum separated from said first frequency spectrum; frequency modulating the carrier wave with said second frequency spectrum; the frequency of said carrier wave being spectrally near to the upper frequency limit of said second frequency spectrum and frequency modulated so that the modulation index is always less than 0.4 and only a single pair of sidebands are produced by each modulating frequency component; frequency translating and filtering the frequency modulated carrier wave so that it has a bandwidth approximating the bandwidth of said first frequency spectrum, said frequency translated and filtered frequency modulated carrier wave containing a constant carrier wave component and lower frequency sidebands, with the carrier component providing a continuously present clocking signal; and transmitting said frequency translated and filtered FM carrier wave to an output channel.
Claim 3
Dependent Claim
23 words
The method for transmitting clocked information set forth in claim 1, wherein the information represented by the first frequency spectrum is video information.
Claim 4
Dependent Claim
53 words
The method for transmitting clocked information set forth in claim 1, wherein the second frequency spectrum is at a higher frequency level than the first frequency spectrum, being separated therefrom by at least 3 mHz; and the carrier wave has a frequency higher than the upper frequency limit of the second frequency spectrum.
Claim 5
Independent Claim
231 words
A method for communicating clocked information by modulation and demodulation of a carrier wave, said method comprising: at the transmitter: frequency translating and filtering a first frequency spectrum containing said clocked information, to provide a second frequency spectrum separated from said first frequency spectrum; frequency modulating the carrier wave with said second frequency spectrum; the frequency of said carrier wave being spectrally near to the upper frequency limit of said second frequency spectrum and frequency modulated so that the modulation index is always less than 0.4 and only a single pair of sidebands is produced by each modulating frequency component, together with a carrier; frequency translating and filtering the frequency modulated carrier wave so that it has a bandwidth, approxiMating the bandwidth of said first frequency spectrum; said frequency translated and filtered frequency modulated carrier wave containing a constant carrier wave component and lower frequency sidebands, with the carrier component providing a continuously present clocking signal; transmitting said frequency translated and filtered FM carrier wave to an output channel; and at the receiver: amplifying said frequency translated FM carrier wave received from said transmission channel; symmetrically limiting the FM carrier wave; demodulating and bandpass filtering the symmetrically limited FM carrier wave to obtain a signal at the receiver representative of the second frequency spectrum of the transmitter; and frequency translating the demodulated second frequency spectrum to obtain said first frequency spectrum.
Claim 6
Independent Claim
231 words
A method for communicating clocked information by modulation and demodulation of a carrier wave, said method comprising: at the transmitter: frequency translating and filtering a first frequency spectrum containing said clocked information, to provide a second frequency spectrum separated from said first frequency spectrum; frequency modulating the carrier wave with said second frequency spectrum; the frequency of said carrier wave being spectrally near to the upper frequency limit of said second frequency spectrum and frequency modulated so that the modulation index is always less than 0.4 and only a single pair of sidebands is produced by each modulating frequency component, together with a carrier; frequency translating and filtering the frequency modulated carrier wave so that it has a bandwidth, approxiMating the bandwidth of said first frequency spectrum; said frequency translated and filtered frequency modulated carrier wave containing a constant carrier wave component and lower frequency sidebands, with the carrier component providing a continuously present clocking signal; transmitting said frequency translated and filtered FM carrier wave to an output channel; and at the receiver: amplifying said frequency translated FM carrier wave received from said transmission channel; symmetrically limiting the FM carrier wave; demodulating and bandpass filtering the symmetrically limited FM carrier wave to obtain a signal at the receiver representative of the second frequency spectrum of the transmitter; and frequency translating the demodulated second frequency spectrum to obtain said first frequency spectrum.
Claim 7
Independent Claim
332 words
A system for transmitting clocked duobinary coded information by frequency modulation, said system comprising: a binary data input; an AND gate for receiving said binary data input; means for providing a stream of clocking pulses to said AND gate; a flip flop having its input connected to the output of said AND gate, and providing a predetermined first signal spectrum at its output; a low bandpass filter coupled to the output of said flip flop to provide a predetermined second signal spectrum approximately one half of and in the lower range of said first signal spectrum; the output of said low bandpass filter being representative of said duobinary coded information; a mixer having a first input thereof connected to the output of said low bandpass filter and a second input connected to a first predetermined transmission reference frequency; said first predetermined frequency applied to said mixer being of such a magnitude that the second signal spectrum at the input of said mixer is translated to a higher frequency level; means for filtering the higher frequency level signal of the mixer to provide a predetermined third signal spectrum separated from and higher than said second signal spectrum; a frequency modulator having one of its inputs connected to the output of said last mentioned filtering means and the other of its inputs connected to a carrier wave of second predetermined transmission reference frequency; said second frequency of said carrier being near to the upper frequency limit of said third signal spectrum so that the third signal spectrum frequency modulates said carrier wave, with a modulation index of less than 0.4; a divider having its input connected to the output of said frequency modulator, for triggering on predetermined edges of the frequency modulated carrier signal; and a vestigial sideband filter having its input connected to said divider for providing only lower sideband at its output; said output signal also including a persistent carrier component of one half said second predetermined frequency, which provides clocking signals.
Claim 8
Independent Claim
332 words
A system for transmitting clocked duobinary coded information by frequency modulation, said system comprising: a binary data input; an AND gate for receiving said binary data input; means for providing a stream of clocking pulses to said AND gate; a flip flop having its input connected to the output of said AND gate, and providing a predetermined first signal spectrum at its output; a low bandpass filter coupled to the output of said flip flop to provide a predetermined second signal spectrum approximately one half of and in the lower range of said first signal spectrum; the output of said low bandpass filter being representative of said duobinary coded information; a mixer having a first input thereof connected to the output of said low bandpass filter and a second input connected to a first predetermined transmission reference frequency; said first predetermined frequency applied to said mixer being of such a magnitude that the second signal spectrum at the input of said mixer is translated to a higher frequency level; means for filtering the higher frequency level signal of the mixer to provide a predetermined third signal spectrum separated from and higher than said second signal spectrum; a frequency modulator having one of its inputs connected to the output of said last mentioned filtering means and the other of its inputs connected to a carrier wave of second predetermined transmission reference frequency; said second frequency of said carrier being near to the upper frequency limit of said third signal spectrum so that the third signal spectrum frequency modulates said carrier wave, with a modulation index of less than 0.4; a divider having its input connected to the output of said frequency modulator, for triggering on predetermined edges of the frequency modulated carrier signal; and a vestigial sideband filter having its input connected to said divider for providing only lower sideband at its output; said output signal also including a persistent carrier component of one half said second predetermined frequency, which provides clocking signals.
Claim 9
Dependent Claim
12 words
The system of claim 5 wherein the gate is an OR gate.
Claim 10
Dependent Claim
254 words
In combination with the system for transmitting clocked duobinary coded information as set forth in claim 6, a system for receiving the recordable transmitted output signal representing said information, the receiving system comprising: an amplifier for increasing the magnitude of said transmitted output signal; an asymmetrical limiter and a tuned circuit connected to the output of said amplifier to obtain a first receiver reference signal representing the second predetermined transmission reference frequency in the transmitted signal; a symmetrical limiter connected to the output of said amplifier for removing amplitude variations from the frequency modulated signal; a demodulator and a bandpass filter connected respectively in series with the output of the symmetrical limiter for frequency translating the signal into a waveform representing the third frequency spectrum of the transmitter, a mixer havinG a first input thereof connected to the output of the last-mentioned bandpass filter and a second input connected to a second receiver reference frequency, to translate the signal downwardly in frequency range into the second frequency spectrum, which represents the transmitted duobinary coded information; the second receiver reference frequency being referenced to said first receiver reference frequency, thereby to assure that the reference frequency for the receiver mixer is the same as the reference frequency for the transmitter mixer; and a detector and amplifier regenerator connected respectively to the output of the mixer to reproduce the binary data input of the receiver; the amplifier/regenerator having a clocking pulse fed thereto from a third receiver reference frequency referenced to said first receiver reference frequency.
Claim 11
Dependent Claim
12 words
The system of claim 7 wherein the gate is an OR gate.
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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) | 1975-10-17 | 1976-04-17 | 1976-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-17 | 1980-04-17 | 1980-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-17 | 1984-04-17 | 1984-10-17 | $7700.00 | Window Closed / Lapsed |