Multi-tone DGPS beacon transmitter and receiver
First Claim
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1. A method for obviating destructive interference between a groundwave and a skywave of a signal, comprising steps of:
- transmitting a first signal having a first carrier frequency propagating from a transmitter as a first signal groundwave and a first signal skywave;
transmitting a second signal having a second carrier frequency having a frequency offset from said first carrier frequency, said second carrier frequency propagating from said transmitter as a second signal groundwave and a second signal skywave; and
using an ionospheric height for calculating said frequency offset for staggering first distances where destructive interference of said first signal groundwave and said first signal skywave occur from second distances where destructive interference between said second signal groundwave and said second signal skywave occur.
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Abstract
An apparatus and a method for transmitting and receiving a signal having multiple tones for obviating destructive interference between a groundwave and a skywave of the signal. The multiple tones have a frequency offset that is calculated so that the destructive interference nulls for each of the tones occurs at different range distances from the transmitter thereby extending the distance over which at least one of the tones can be reliably received.
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Citations
36 Claims
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1. A method for obviating destructive interference between a groundwave and a skywave of a signal, comprising steps of:
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transmitting a first signal having a first carrier frequency propagating from a transmitter as a first signal groundwave and a first signal skywave; transmitting a second signal having a second carrier frequency having a frequency offset from said first carrier frequency, said second carrier frequency propagating from said transmitter as a second signal groundwave and a second signal skywave; and using an ionospheric height for calculating said frequency offset for staggering first distances where destructive interference of said first signal groundwave and said first signal skywave occur from second distances where destructive interference between said second signal groundwave and said second signal skywave occur. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A transmitter station for transmitting at least two signals for obviating destructive interference between a groundwave and a skywave of a signal for extending a selected range from the transmitter station, comprising:
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a transmitter for transmitting a first signal and a second signal, said first signal propagating as a first signal groundwave and a first signal skywave and said second signal propagating as a second signal groundwave and a second signal skywave; a first signal generator connected to the transmitter for providing said first signal having a first carrier frequency; and a second signal generator connected to the transmitter for providing said second signal having a second carrier frequency differing from said first signal carrier frequency by a frequency offset, said frequency offset calculated from an ionospheric height for staggering first distances where destructive interference of said first signal groundwave and said first signal skywave occurs from second distances where destructive interference between said second signal groundwave and said second signal skywave occurs. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method for obviating destructive interference by receiving a multi-tone signal, comprising steps of:
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receiving a first signal having information modulated onto a first carrier frequency, said first signal propagating from a transmitter as a first signal groundwave and a first signal skywave; receiving a second signal having said information modulated onto a second carrier frequency, said second signal propagating from said transmitter as a second signal groundwave and a second signal skywave, said second carrier frequency differing from said first carrier frequency by a frequency offset calculated from an ionospheric height for staggering first distances from said transmitter where destructive interference of said first signal groundwave and said first signal skywave occur from second distances where destructive interference between said second signal groundwave and said second signal skywave occur; and processing said first and said second signals for recovering said information from at least one of said first signal and said second signal. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A receiver for obviating destructive interference by receiving a multi-tone signal, comprising:
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a first tuner for tuning to a first signal having information modulated onto a first carrier frequency propagating from a transmitter as a first signal groundwave and a first signal skywave; a second tuner for tuning to a second signal having said information modulated onto a second carrier frequency propagating from said transmitter as a second signal groundwave and a second signal skywave, said second carrier frequency and said first carrier frequency having a frequency offset calculated from an ionospheric height for extending the range where destructive interference of said first signal groundwave and said first signal skywave and destructive interference between said second signal groundwave and said second signal skywave do not simultaneously occur; and selection means coupled to the first and second tuners for selecting at least one of said first and said second signals for recovering said information. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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Specification