Acquisition signal transmitter
First Claim
1. A transmitter including:
- means for generating a radio frequency carrier;
means for generating an encoded information bearing signal, said means including the amplitude modulation of said carrier;
means for generating an acquisition signal, said means including the amplitude modulation of said carrier by a constant frequency waveform, said acquisition signal providing enhanced signal acquisition and interference rejection capability favoring said information bearing signal in an environment where there may be multiple signals in the same frequency band as said information bearing signal and having substantially all of its transmitted spectral power, in terms of frequency, very close to, but displaced from, the transmitted spectral power of said radio frequency carrier; and
means to sequentially transmit both said acquisition signal and said information bearing signal.
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Accused Products
Abstract
An encoded information transmitter which transmits a radio frequency carrier that is amplitude modulated by a constant frequency waveform and thereafter amplitude modulated by a predetermined encoded waveform, the constant frequency waveform modulated carrier constituting an acquisition signal and the encoded waveform modulated carrier constituting an information bearing signal, the acquisition signal providing enhanced signal acquisition and interference rejection favoring the information bearing signal. One specific application for this transmitter is as a distress transmitter where a conventional, legislated audio tone modulated signal is transmitted followed first by the acquisition signal and then the information bearing signal, the information bearing signal being encoded with, among other things, vehicle identification data. The acquistion signal enables a receiver to acquire the information bearing signal where the received signal is low and/or where the received signal has a low signal-to-noise ratio in an environment where there are multiple signals in the same frequency band as the information bearing signal.
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Citations
14 Claims
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1. A transmitter including:
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means for generating a radio frequency carrier; means for generating an encoded information bearing signal, said means including the amplitude modulation of said carrier; means for generating an acquisition signal, said means including the amplitude modulation of said carrier by a constant frequency waveform, said acquisition signal providing enhanced signal acquisition and interference rejection capability favoring said information bearing signal in an environment where there may be multiple signals in the same frequency band as said information bearing signal and having substantially all of its transmitted spectral power, in terms of frequency, very close to, but displaced from, the transmitted spectral power of said radio frequency carrier; and means to sequentially transmit both said acquisition signal and said information bearing signal. - View Dependent Claims (2, 3, 4, 5)
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6. A vehicle borne distress transmitter including:
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means for generating a radio frequency carrier; means for generating a distress signal, said means including the amplitude modulation of said carrier; means for generating an information bearing signal, said means including the amplitude modulation of said carrier; means for generating an acquisition signal, said means including the amplitude modulation of said carrier and said modulation being provided by a constant frequency waveform, said acquisition signal providing enhanced signal acquisition and interference rejection favoring said information bearing signal in an environment where there are multiple signals in the same frequency band as the information bearing signal; and means to sequentially transmit said distress signal, said information bearing signal and said acquisition signal, said acquisition signal immediately preceding, in terms of the time or order of transmission, said information bearing signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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Specification