Direction finding and mobile location system for trunked mobile radio systems
First Claim
1. A mobile radio location system, comprising:
- a mobile radio having a unique identifier, and having a transmitter for sending a message on one or more selected frequency channels selected from a set of available frequency channels and for coordinating selection of the one or more selected frequency channels on a control channel;
a first base station having a first array of irregularly spaced antennas operable for receiving the message on the one or more selected frequency channels, operable for receiving control information on the control channel and capable of determining a first direction of origin of the message by phase differences measurements on the array of irregularly spaced antennas using interferometric direction finding;
a second base station having a second array of irregularly spaced antennas operable for receiving the message on the one or more selected frequency channels, operable for receiving control information on the control channel and capable of determining a second direction of origin of the message by phase differences measurements on the second array of irregularly spaced antennas using interferometric direction finding; and
a central station connected to the first base station and the second base station, and operable for;
1.) receiving the first direction of origin of the message from the first base station;
2.) receiving the second direction of origin of the message from the second base station;
3.) triangulating the first direction with the second direction to determine the location.
2 Assignments
0 Petitions
Accused Products
Abstract
A special mobile radio mobile, vehicle or personal location system is described where the system operates to locate any one of a the transmitters in an SMR system. The present invention operates by identifying the received signals, removing the modulation information to reconstruct a demodulated carrier and analyzing the carrier signals for multipath distortion. The multipath disruptions are removed to calculate the true incident angle of the transmitted signal at a base station. A plurality of base stations are used to simultaneously calculate the incident angle of the transmitted SMR signal and a central location calculates the most probable location of the transmitter based upon triangulation. The incident angle of the transmitted SMR signal at each base station is performed by calculating the phase differences of the incoming voice signal with phase ambiguity minimized by using a plurality of dipole antennas spaced at an irregular distance to eliminate phase ambiguity error.
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Citations
8 Claims
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1. A mobile radio location system, comprising:
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a mobile radio having a unique identifier, and having a transmitter for sending a message on one or more selected frequency channels selected from a set of available frequency channels and for coordinating selection of the one or more selected frequency channels on a control channel; a first base station having a first array of irregularly spaced antennas operable for receiving the message on the one or more selected frequency channels, operable for receiving control information on the control channel and capable of determining a first direction of origin of the message by phase differences measurements on the array of irregularly spaced antennas using interferometric direction finding; a second base station having a second array of irregularly spaced antennas operable for receiving the message on the one or more selected frequency channels, operable for receiving control information on the control channel and capable of determining a second direction of origin of the message by phase differences measurements on the second array of irregularly spaced antennas using interferometric direction finding; and a central station connected to the first base station and the second base station, and operable for; 1.) receiving the first direction of origin of the message from the first base station; 2.) receiving the second direction of origin of the message from the second base station; 3.) triangulating the first direction with the second direction to determine the location. - View Dependent Claims (2, 3, 7)
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4. A special mobile radio location system, comprising:
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a special mobile radio having a unique identifier, and having a transmitter for sending a message on one or more selected frequency channels selected from a set of available frequency channels and for coordinating selection of the one or more selected frequency channels on a control channel; a first base station having an array of irregularly spaced antennas operable for receiving the message on the one or more selected frequency channels, operable for receiving control information on the control channel and capable of determining a first direction of origin of the message; a second base station also having an array of irregularly spaced antennas operable for receiving the message on the one or more selected frequency channels, operable for receiving control information on the control channel and capable of determining a second direction of origin of the message; a central station connected to the first base station and the second base station, and operable for; 1.) receiving the first direction of origin of the message from the first base station; 2.) receiving the second direction of origin of the message from the second base station; - View Dependent Claims (6)
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5. ) triangulating the first direction with the second direction to determine the location;
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wherein the first base station and the second base station both operate to reduce the ambiguity of the direction of arrival of the incoming signal by calculating a multidimensional ambiguity space having lines indicating the only possible angles of the direction of arrival of the signal and determining the probable points of these lines which are closest to the observed value.
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8. A method of locating a trunked mobile transmitter, comprising the steps of:
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a.) receiving at a first base station a trunked radio frequency signal on a plurality of irregularly spaced antennas; b.) removing the modulation information to produce a demodulated radio frequency carrier signal; c.) calculating the observed angle of arrival of the demodulated radio frequency carrier signal by comparing the phase difference of the demodulated radio frequency carrier signal between pairs of the plurality of irregularly spaced antennas; d.) determining the most probable angle of arrival of the demodulated radio frequency carrier signal by comparing the observed angle of arrival to ambiguity lines in an n-dimensional space where the number of antennas is n+1; e.) repeating steps a.-d. for each of a plurality of base stations to produce a plurality of most probable angles of arrivals; f.) calculating an histogram of the plurality of most probable angles of arrivals and selecting the strongest most probable values; and g.) applying a spatial filter to the strongest most probable values from each base station and selecting the location based on the closest grouping of the strongest most probable values.
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Specification