LORAN-C navigation apparatus
First Claim
1. Navigation receiver-indicator providing navigation information by receiving and measuring differences in the time of arrival of signals transmitted by a plurality of pairs of transmitters and the difference measurements are plotted on a navigation chart to determine position, comprisingmeans for determining the signal transmission from the first station to transmit of one of said pairs of transmitters and generating a first signal in response thereto,first means manually operable to indicate the approximate time period between the arrival of signals from said first station and the arrival of signals from the second station to transmit of said one of said pairs of transmitters, andfirst means operable in response to said first signal and to said approximate time period indicated by said first indicating means to measure the difference in time of arrival at said receiver-indicator between signals received from said first station and signals received from said second station within a first time period starting at the end of said approximate time period and to provide an output indicating said difference in time of arrival measurement.
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Accused Products
Abstract
LORAN-C navigation equipment is disclosed wherein digital circuitry is used to automatically distinguish a master LORAN-C transmitting station from a secondary station. The equipment operator manually enters approximate time difference of signal arrival information for a particular secondary station into the equipment after consulting a LORAN-C chart. The operator then manually determines the exact time difference of arrival using thumbwheel switches and a LED lamp display. This procedure is repeated to determine exact time difference of arrival information for the master and each selected secondary station, and the information is plotted in a well-known manner on the LORAN-C chart to locate the position of the craft upon which the equipment is located. Manual acqisition of secondary stations simplifies the equipment and eliminates interference problems caused by skywaves and other transmissions. The set oscillator is easily and quickly calibrated by the operator who manually enters the LORAN-C chain group repetition interval information found on the LORAN-C chart on the thumbwheel switches of the receiver and then adjusts the oscillator for a match as indicated on the LED display.
10 Citations
26 Claims
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1. Navigation receiver-indicator providing navigation information by receiving and measuring differences in the time of arrival of signals transmitted by a plurality of pairs of transmitters and the difference measurements are plotted on a navigation chart to determine position, comprising
means for determining the signal transmission from the first station to transmit of one of said pairs of transmitters and generating a first signal in response thereto, first means manually operable to indicate the approximate time period between the arrival of signals from said first station and the arrival of signals from the second station to transmit of said one of said pairs of transmitters, and first means operable in response to said first signal and to said approximate time period indicated by said first indicating means to measure the difference in time of arrival at said receiver-indicator between signals received from said first station and signals received from said second station within a first time period starting at the end of said approximate time period and to provide an output indicating said difference in time of arrival measurement.
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8. A LORAN navigation receiver-indicator for receiving repetitive pulse train signals from a master and a plurality of secondary LORAN transmitting stations and measuring the time between the arrival of the signals received from the master station and the signals received from at least two secondary stations to determine the position of the receiver-indicator comprising
first logic circuitry for determining that the received pulse train signals are from a master or a secondary station and generating a first signal in response thereto, second logic circuitry for determining that the received pulse train signals are from said master station and generating a second signal in response thereto, a clock generating a pulse train, a counter driven by said clock, having a plurality of counter stages, and counter normally being disabled from counting but being enabled to count responsive to said first signal, said counter being disabled from counting and being reset to zero upon counting to a first count without said second signal being generated, and counter being enabled to continue counting responsive to said second signal being generated prior to said counter counting to said first count, said counter being disabled from counting and being reset to zero after having been enabled to continue counting upon a manually determined second count being in said counter, a plurality of manually operable multi-position switches each providing a numerical output signal indicating the setting of the switch, one of said switches being associated with each of said plurality of counter stages, a first plurality of two input comparators each comparing the contents of higher order ones of said pluraity of counter stages applied to a first input with the numerical output signal of the associated one of said switches applied to a second input and providing a third signal output only upon the signals at the two inputs being numerically equal, a second plurality of two input comparators each comparing the contents of lower order ones of said plurality of counter stages applied to a first input with the numerical output signal of the associated one of said switches being applied to a second input count and providing fourth output signals indicating which of the two input count signals is numerically greater or they are equal, said second plurality of comparators being enabled only in response to said third signal from said first plurality of comparators, said fourth output signals providing an indication of changes to be made in the settings of said switches associated with said second plurality of comparators so that said fourth output signals indicate that the inputs to said second plurality of comparators are equal, and the settings of said switches indicate the time period between the arrival of the pulse trains from said master station and a selected secondary station.
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22. A method of deriving position information for navigation purposes by making measurements of the time period between receipt of signals from a first or master transmitting station and selected ones of a plurality of secondary transmitting stations in a navigation system comprising steps of,
checking signals received from said master and said secondary stations to determine which of the received signals is from said master station and which of the received signals is from one of said secondary stations, manually selecting a first time period only in which the received signals from a selected one of said plurality of secondary stations will be recognized after consulting a navigation chart having time period information thereon for the approximate geographical location of equipment performing this method, and measuring the time period between receipt of the signals from said master station and the signals from said selected one of said secondary stations received in said manually selected first time period to derive said navigation position information.
Specification