Robust low-frequency spread-spectrum navigation system
First Claim
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1. A radiolocation receiver, comprising:
- a first decoder configured to receive an input comprising radiolocation data from a plurality of different transmitters, where the first decoder is configured to demodulate the input and extract radiolocation data transmitted from at least one transmitter of the plurality of transmitters;
a remodulator coupled to an output of the first decoder and configured to remodulate an output signal received from the first decoder;
a summer coupled to an output of the remodulator and configured to subtract an output signal of the remodulator from the input received at the first decoder; and
a second decoder coupled to an output of the summer and configured to demodulate an output signal of the summer and extract radiolocation data transmitted from at least one other transmitter.
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Abstract
Methods and apparatus are described for a navigation system. A process includes providing a plurality of transmitters distributed throughout a desired coverage area; locking the plurality of transmitters to a common timing reference; transmitting a signal from each of the plurality of transmitters. An apparatus includes a plurality of transmitters distributed throughout a desired coverage area; wherein each of the plurality of transmitters comprises a packet generator; and wherein the plurality of transmitters are locked to a common timing reference.
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Citations
15 Claims
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1. A radiolocation receiver, comprising:
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a first decoder configured to receive an input comprising radiolocation data from a plurality of different transmitters, where the first decoder is configured to demodulate the input and extract radiolocation data transmitted from at least one transmitter of the plurality of transmitters; a remodulator coupled to an output of the first decoder and configured to remodulate an output signal received from the first decoder; a summer coupled to an output of the remodulator and configured to subtract an output signal of the remodulator from the input received at the first decoder; and a second decoder coupled to an output of the summer and configured to demodulate an output signal of the summer and extract radiolocation data transmitted from at least one other transmitter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15)
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11. A radiolocation receiver, comprising:
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an antenna; an RF amplifier coupled to the antenna; a bandpass filter coupled to the RF amplifier; an analog-to-digital converter coupled to the bandpass filter; a numerically controlled oscillator coupled to the analog-to-digital converter; a first and a second mixer/multiplier coupled to the numerically controlled oscillator; a first programmable delay register and downsampling component coupled to the first mixer/multiplier; a second programmable delay register and downsampling component coupled to the second mixer/multiplier; a first correlator coupled to the first programmable delay register and downsampling component; a second correlator coupled to the second programmable delay register and downsampling component; a delay lock loop coupled to the first correlator and the second correlator; a rectangular to polar converter coupled to the first correlator and the second correlator; a detector coupled to the rectangular to polar converter; and a data decoder coupled to the rectangular to polar converter, where the data decoder comprises an extended Costas loop demodulator.
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12. A multiple-channel radiolocation receiver, comprising:
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a first spread-spectrum correlator configured to apply a first spreading code to a first radiolocation signal and obtain a ground-wave radiolocation signal; a second spread-spectrum correlator associated with the first spread-spectrum correlator and configured to apply the spreading code to a second radiolocation signal and obtain a sky-wave radiolocation signal; and a processor configured to receive outputs from the first spread-spectrum correlator and the second spread-spectrum correlator, the processor programmed to compute a composite three-dimensional location and time solution for the receiver, and where the processor is programmed to compute a height of the receiver from a differential delay figure between the sky-wave radiolocation signal and the ground-wave radiolocation signal. - View Dependent Claims (13, 14)
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Specification