LORAN-C navigation apparatus
First Claim
1. A navigation receiver-indicator providing navigation information by receiving and measuring differences in the time of arrival of coded radio signals received from a plurality of navigation transmitters, in groups of transmitters, comprising:
- means for selecting a group of transmitters to be used for said time difference of arrival measurements,first logic means processing said radio signals as they are received for determining when received signals are properly coded indicating they are from said navigation transmitters,and providing output indications of same,processor means storing and analyzing said output indications from said first logic means to determine when received radio signals are from transmitters of a group of transmitters selected using said selecting means, andsecond logic means enabled by and functioning with said processor means after said processor means has determined that received radio signals are from said selected group of transmitters to calculate the time of reception of subsequently received radio signals and then to analyze said last-mentioned radio signals to thereby locate a specific point of said last-mentioned radio signals used by said processor means to accurately measure the difference in time .Iadd.of .Iaddend.arrival of said radio signals from individual transmitters of said selected group of transmitters and provide a visual output of said measurements to provide navigation information.
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Accused Products
Abstract
LORAN-C navigation apparatus is disclosed wherein digital circuitry and a microprocessor .[.is.]. .Iadd.are .Iaddend.used to automatically identify LORAN transmitting stations and .[.makes.]. .Iadd.make .Iaddend.standard hyberbolic navigation measurements. The equipment operator manually enters the group repetition rate into the apparatus for a LORAN-C chain covering the area within which the navigation apparatus is being operated. Initially, the apparatus searches all incoming signals .Iadd.as they are received .Iaddend.until signals from a master station are received regularly at the stored group repetition rate. The apparatus then closely determines the time of arrival of signals from the secondary stations of the selected LORAN-C chain before changing to a fine search mode in which the exact time of arrival of the secondary station signals is determined; the phase code of the received signals is checked to determine if the received signal is a ground or sky wave, and a determination is made if there is a defective secondary station blink code. The time difference of arrival measurements are then output visually to be plotted in a well known manner on a LORAN-C chart to locate the position of the craft upon which the apparatus is located.
40 Citations
20 Claims
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1. A navigation receiver-indicator providing navigation information by receiving and measuring differences in the time of arrival of coded radio signals received from a plurality of navigation transmitters, in groups of transmitters, comprising:
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means for selecting a group of transmitters to be used for said time difference of arrival measurements, first logic means processing said radio signals as they are received for determining when received signals are properly coded indicating they are from said navigation transmitters, and providing output indications of same, processor means storing and analyzing said output indications from said first logic means to determine when received radio signals are from transmitters of a group of transmitters selected using said selecting means, and second logic means enabled by and functioning with said processor means after said processor means has determined that received radio signals are from said selected group of transmitters to calculate the time of reception of subsequently received radio signals and then to analyze said last-mentioned radio signals to thereby locate a specific point of said last-mentioned radio signals used by said processor means to accurately measure the difference in time .Iadd.of .Iaddend.arrival of said radio signals from individual transmitters of said selected group of transmitters and provide a visual output of said measurements to provide navigation information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for deriving position information for navigation purposes by making measurements of the time period between receipt of periodic signals in pulse trains from a selected first or master transmitting station and selected ones of a plurality of secondary transmitting stations associated with said master station in a navigation system comprising the steps of:
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analyzing the makeup of each pulse train as it is being received to determine if it is from a master or secondary station, storing an indication of the time of receipt of each pulse train along with an indication whether it is from a master or secondary station, said stored indications being used to identify said selected master station and its associated secondary stations, calculating the time of receipt of signals subsequently received from said selected master station and said secondary stations after determining which periodic signals are received therefrom, analyzing each signal received at the indicated times of arrival from said selected master station and said secondary stations to determine if the indicated time of arrival is correct and to modify said indicated times of arrival if necessary to locate a specific point in each of said periodic signals. measuring the difference in time of arrival between the specific point of each of the periodic signals received from said master station and each of the selected secondary stations, and providing an output reflecting said time difference of signal arrival measurement used for navigation purposes. - View Dependent Claims (14, 15, 16, 17)
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19. Iadd.30. The invention in accordance with claim 29 wherein said analyzing means further includes
means for converting each pulse of said pulse trains from said transmitters as they are received to corresponding binary digital signals, and wherein said shifting means continuously shifts said binary digital signals through said shift register means. .Iaddend. .Iadd.31. The invention in accordance with claim 30 wherein each pulse of said pulse trains comprises a plurality of cycles of a radio frequency carrier of fixed frequency, and wherein said shifting means shifts said binary digital signals through said shift register at a rate at least equal to said fixed carrier frequency. .Iaddend. .Iadd.32. The invention in accordance with claim 30 wherein said decoding means comprises logic gate means responsive to the time coincidence of binary digital signals at each of said outputs from shift register means for providing said output indication. .Iaddend. .Iadd.33. The invention in accordance with claim 30 wherein said shift register means includes a plurality of stages connected in series, each of said stages including a plurality of binary digit storage locations, and wherein said extracting means extracts an output from each of said stages. .Iaddend. .Iadd.34. The invention in accordance with claim 29 wherein the individual pulses of said pulse trains are phase coded with the pulse phase codes being different for different ones of said transmitters in said group, and wherein said analyzing means further includes means for inverting selected ones of said outputs from said shift register means prior to the application thereof to said decoding means. .Iaddend. .Iadd.35. A method of providing navigation information by receiving and measuring differences in the time of arrival of radio frequency pulse trains periodically transmitted by a plurality of navigation transmitters in a group, the individual pulses in each of said pulse trains having a known pulse repetition rate, said method comprising the steps of: -
analyzing pulse trains as they are received to determine when a given pulse train being received is from one of said transmitters, said analyzing step including the steps of continuously shifting the pulses of said pulse trains as they are received through shift register means of sufficient length to contain a window time sample of duration at least as long as that of one of said pulse trains from one of said transmitters, extracting a plurality of outputs from said shift register means at points spaced apart by the known pulse repetition rate, and decoding said outputs from said shift register means to provide an output indication whenever said pulse train contained in said shift register means corresponds to one from said transmitters; and processing said output indications to measure the difference in the time of arrival of said pulse trains from individual ones of said transmitters in - View Dependent Claims (18)
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20. said group. .Iaddend. .Iadd.36. The method in accordance with claim 35 wherein said analyzing step further includes the step of
converting each pulse of said pulse trains as they are received to corresponding binary digital signals, and wherein said shifting step comprises the step of continuously shifting said binary digital signals through said shift register means. .Iaddend. .Iadd.37. The method in accordance with claim 36 wherein each pulse of said pulse trains comprises a plurality of cycles of a radio frequency carrier of fixed frequency, and wherein said shifting step comprises the step of shifting said binary digital signals through said shift register means at a rate at least equal to said fixed carrier frequency. .Iaddend. .Iadd.38. The method in accordance with claim 36 wherein said decoding step comprises the step of providing said output indication in response to the time coincidence of binary digital signals at each of said outputs from said shift register means. .Iaddend. .Iadd.39. The method in accordance with claim 35 wherein the individual pulses of said pulse are phase coded with the pulse phase codes being different for different ones of said transmitters in said group, and wherein said analyzing step further includes the step of inverting selected ones of said outputs from said shift register means prior to the operation of said decoding step..Iaddend.
Specification