Abstract A process for frequency modulation of binary messages in which the variables 0 and 1 are represented by signals of respective frequencies f0 and f1 differing by frequency Delta f. The process is characterized in that, to prevent undesirable phase modulation during the switching from one frequency to the other, frequency f1 is related to frequency f0 by deriving the signal of frequency f1 from a carrier wave form at the frequency f0 through modulation of such frequency f0 to obtain a single sideband by means of a signal of frequency Delta f which determines the rate of the switching intervals of the binary message. The apparatus comprises a first generator providing a carrier wave form of frequency fo, a first phase shifting circuit providing two first signals of frequency f0 shifted by 90*, a second generator providing a signal of frequency Delta f, a second phase shifting circuit providing two second signals phased 90* from each other, two modulators for amplitude modulating the two first signals by the two second signals respectively, an adding circuit for adding the outputs of said two modulators and having means for suppressing one of the sidebands and the carrier waveform so as to generate a signal of frequency f1, an electronic switching means operated at the frequency Delta f or a submultiple thereof for switching the signals of frequencies f0 and f1 in accordance with the message to be transmitted.
Inventors
👤 Jean-Marie De Rubinat
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-01 14:24
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/12
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
79 words
Process for transmission of binary messages by frequency shift keying synchronized with the transitions of the messages, whereby the two frequencies used are tied together by using single sideband modulation of a carrier wave in order to avoid undesirable phase modulation, comprising the step of selecting respectively, for the two frequencies, the carrier wave and one of the two sidebands of said carrier wave modulated by a signal having a frequency equal to the difference of said two frequencies.
Claim 2
Dependent Claim
79 words
Process for transmission of binary messages by frequency shift keying synchronized with the transitions of the messages, whereby the two frequencies used are tied together by using single sideband modulation of a carrier wave in order to avoid undesirable phase modulation, comprising the step of selecting respectively, for the two frequencies, the carrier wave and one of the two sidebands of said carrier wave modulated by a signal having a frequency equal to the difference of said two frequencies.
Claim 3
Dependent Claim
101 words
In an apparatus for transmission of binary messages by frequency shift keying synchronized with the transitions of the messages, including a carrier wave generator, a low frequency signal generator for modulating said carrier wave, and means responsive to said carrier wave generator and to said low frequency signal generator for generating one single sideband signal, the improvement comprising means for switching, at the output terminals of such apparatus, said carrier wave and said single sideband signals according to the data of the message to be transmitted, and means for operating said switching means at the rate of said low frequency signal.
Claim 4
Dependent Claim
101 words
In an apparatus for transmission of binary messages by frequency shift keying synchronized with the transitions of the messages, including a carrier wave generator, a low frequency signal generator for modulating said carrier wave, and means responsive to said carrier wave generator and to said low frequency signal generator for generating one single sideband signal, the improvement comprising means for switching, at the output terminals of such apparatus, said carrier wave and said single sideband signals according to the data of the message to be transmitted, and means for operating said switching means at the rate of said low frequency signal.