Methods and apparatus for reducing intelligible crosstalk in single sideband radio systems
First Claim
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1. In a transmission system of the type wherein information is transmitted from a first to a second location, said system including, at said first location:
- means for generating a carrier wave; and
means for modulating the amplitude of said carrier wave with said information, the improvement which comprises;
means for generating a coding signal; and
means, positioned intermediate said carrier wave generating means and said amplitude modulating means, for phase-modulating said carrier wave with said coding signal thereby to encode the amplitude-modulated output of said modulating means whereby any interfering signal which enters the transmission system and which is not similarly encoded is spread, in the frequency domain, and thus rendered unintelligible.
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Abstract
Intelligible crosstalk in microwave radio systems employing single-sideband modulation is substantially eliminated by phase-modulating the AM carrier-wave prior to its modulation by the baseband signal. The phase-modulation may comprise a periodic signal, such as a single sinusoidal tone or pseudo-random noise, or it may comprise an aperiodic signal such as a truly random noise. In this latter event, the coding signal is transmitted to the receiving location to ensure proper demodulation of the encoded signal.
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Citations
46 Claims
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1. In a transmission system of the type wherein information is transmitted from a first to a second location, said system including, at said first location:
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means for generating a carrier wave; and means for modulating the amplitude of said carrier wave with said information, the improvement which comprises; means for generating a coding signal; and means, positioned intermediate said carrier wave generating means and said amplitude modulating means, for phase-modulating said carrier wave with said coding signal thereby to encode the amplitude-modulated output of said modulating means whereby any interfering signal which enters the transmission system and which is not similarly encoded is spread, in the frequency domain, and thus rendered unintelligible. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In a transmission system of the type wherein a coded, amplitude-modulated signal is transmitted from a first to a second location, said system including, at said second location:
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means for generating a local carrier wave; and means, connected to said local carrier wave generating means, for demodulating said amplitude-modulated signal, the improvement which comprises; means for generating a local coding signal which corresponds to the signal priorly employed at said first location to encode said amplitude-modulated signal; and means for phase-modulating said local carrier wave with said local coding signal, thereby to cause said demodulating means to decode said coded amplitude-modulated signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. In a method of transmitting information from a first to a second location of the type that includes the steps of:
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generating a carrier wave; and modulating the amplitude of said carrier wave with the information to be transmitted, the improvement which comprises the steps of; generating a coding signal; and
then,phase-modulating said carrier wave with said coding signal prior to modulating the amplitude thereof with the information signal. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. In a method of transmitting information in the form of a coded, amplitude-modulated signal from a first to a second location of the type that includes the steps of, at said second location:
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generating a local carrier wave; and demodulating said amplitude-modulated signal by use of said local carrier wave, the improvement which comprises the steps of; generating a local coding signal which corresponds to the signal priorly employed at said first location to encode said amplitude-modulated signal; and
thenphase-modulating said local carrier wave with said local coding signal thereby to ensure proper demodulation of said coded, amplitude-modulated signal. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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Specification