Methods and apparatus for reducing intelligible crosstalk in single sideband radio systems
AssigneeBell Telephone Laboratories, Incorporated
InventorRichard Barry Swerdlow
Life of this patent
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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.
Claims46
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.
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:
- 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.
In a method of transmitting information from a first to a second location of the type that includes the steps of:
- 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.
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:
- 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 then
- phase-modulating said local carrier wave with said local coding signal thereby to ensure proper demodulation of said coded, amplitude-modulated signal.
Dependencies are inferred from the claim text.