Collision avoidance/proximity warning system using secondary radar
First Claim
Patent Images
1. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said apparatus comprising in combination:
- a. direction-finding antenna means for receiving transponder replies transmitted by said other transponder station;
b. direction-finding means, connected to said antenna means, for indicating the angle of incidence of said transponder replies on said antenna means;
c. receiver means for detecting interrogations transmitted by a ground station when said beam is directed thereto; and
d. timing means, connected to said receiver means, for enabling said direction-finding means to indicate said angle of incidence of a transponder reply to an interrogation after a predetermined period following the time that said interrogation would be received if said beam were directed at said receiver means;
whereby the bearing to said other transponder station is indicated only if replies from such transponder station are received after said predetermined period.
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Abstract
Proximity indication and evaluation of mobile vehicles, using the signals emitted by the hundreds of existing secondary radar ground stations and the nearly 100,000 cooperating transponders on the vehicles, to detect intrusion in a monitored proximity volume and to determine slant range and/or relative bearing to the intruder.
109 Citations
51 Claims
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1. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said apparatus comprising in combination:
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a. direction-finding antenna means for receiving transponder replies transmitted by said other transponder station; b. direction-finding means, connected to said antenna means, for indicating the angle of incidence of said transponder replies on said antenna means; c. receiver means for detecting interrogations transmitted by a ground station when said beam is directed thereto; and d. timing means, connected to said receiver means, for enabling said direction-finding means to indicate said angle of incidence of a transponder reply to an interrogation after a predetermined period following the time that said interrogation would be received if said beam were directed at said receiver means;
whereby the bearing to said other transponder station is indicated only if replies from such transponder station are received after said predetermined period.
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2. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said apparatus comprising, in combination:
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a. direction-finding antenna means for receiving transponder replies transmitted by said other transponder station; b. direction-finding means, connected to said antenna means, for indicating the angle of incidence of said transponder replies on said antenna means; c. receiver means for detecting interrogations transmitted by a ground station when said beam is directed thereto; and d. timing means, connected to said receiver means, for disabling said direction-finding means from indicating said angle of incidence of a transponder reply to an interrogation after a predetermined period following the time that said interrogation would be received if said beam were directed at said receiver means; whereby the bearing to said other transponder station is indicated only if replies from such transponder station are received before said predetermined period.
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3. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said apparatus comprising, in combination:
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(a) direction-finding antenna means for receiving transponder replies transmitted by said other transponder station; (b) direction-finding means, connected to said antenna means, for indicating the angle of incidence of said transponder replies on said antenna means; (c) receiver means for detecting interrogations transmitted by a ground station when said beam is directed thereto; and (d) timing means, connected to said receiver means, for enabling said direction-finding means to indicate said angle of incidence of a transponder reply to an interrogation during a predetermined period following the time that said interrogation would be received if said beam were directed at said receiver means; whereby the bearing to said other transponder station is indicated only if such transponder station is located within a selected region of space. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said apparatus comprising, in combination:
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(a) direction-finding antenna means for receiving transponder replies transmitted by said other transponder station; (b) direction-finding means, connected to said antenna means, for determining the angle of incidence of said transponder replies on said antenna means; (c) first receiver means for detecting interrogations transmitted by the ground stations when the beams thereof sweep by said own station; (d) means, connected to said first receiver means, for determining the angle of incidence on said own station of interrogations received from one of said ground stations; (e) second receiver means for detecting transponder replies transmitted by said other transponder station; (f) timer means, connected to said first and said second receiver means, for determining the difference (TD) between the time that an interrogation would be received if the beam of said one ground station were directed at said first receiver means, and the time of receipt of a transponder reply to that interrogation; (g) logic means, connected to said angle determining means and to said timer means, for determining the slant range from said own station to said other transponder station without transmission from said own station; and (h) means, connected to said direction-finding means, said second receiver means and to said logic means, for indicating said angle of incidence of a transponder reply of, and said slant range to, said other transponder station if said transponder reply is received during a predetermined period following the time that the interrogation which elicited such reply would be received if its beam were directed at said own station. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said ground stations omni-directionally transmitting a reference signal as the respective beams thereof sweep through a standardized reference direction, such as magnetic North, said apparatus comprising, in combination:
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(a) direction-finding antenna means for receiving transponder replies transmitted by said other transponder station; (b) direction-finding means, connected to said antenna means, for determining the angle of incidence of said transponder replies on said antenna means; (c) first receiver means for receiving said reference signals and said interrogations transmitted by said ground stations and producing an output responsive only to the reference signal and interrogations of a selected one of said ground stations; and (d) first timer means, connected to said first receiver means, for determining the elapsed time between the receipt of said reference signal and said interrogations for a given beam rotation of said selected ground station; whereby said time is proportional to the azimuth of said beam of said selected ground station when it is directed at said first receiver means. - View Dependent Claims (28, 29)
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30. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said ground stations omni-directionally transmitting a reference signal as the respective beams thereof sweep through a standardized reference direction, such as magnetic North, said apparatus comprising, in combination:
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(a) direction-finding antenna means for receiving transponder replies transmitted by said other transponder station; (b) direction-finding means, connected to said antenna means, for determining the angle of incidence of said transponder replies on said antenna means; (c) first receiver means for receiving said reference signals and said interrogations transmitted by said ground stations and producing an output responsive only to the reference signal and interrogations of a selected one of said ground stations; (d) first timer means, connected to said first receiver means, for determining the elapsed time between the receipt of said reference signal and said interrogations for a given beam rotation of said selected ground station; (e) second receiver means for detecting transponder replies transmitted by said other transponder station;
(f) second timer means, connected to said first and second receiver means, for determining the difference (TD) between the time that a interrogation would be received if said beam were directed at said first receiver means, and the time of receipt of a transponder reply to said interrogation;(g) logic means, connected to said direction-finding means and to said second timer means, for determining the slant range from said own station to said other transponder station without transmission from said own station. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A process for detecting at an "own" station the proximity of mobile, transponder-carrying vehicles in an azimuthally scanning secondary surveillance radar (SSR) system wherein vehicle transponders in the proximity of said own station reply to interrogations transmitted in a narrow, rotating beam of at least one ground station remote from said own station and said vehicle transponders, said process comprising the steps of:
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(a) receiving transponder replies to an interrogation at said own station during a predetermined period following the time that said interrogation would be received if said beam were directed toward said own station; and (b) determining the angle of incidence of said transponder replies received during said predetermined period. - View Dependent Claims (41, 42, 43, 44, 45)
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46. A process for detecting at an "own" station the proximity of mobile, transponder-carrying vehicles in an azimuthally scanning secondary surveillance radar (SSR) system wherein vehicle transponders in the proximity of said own station reply to interrogations transmitted in a narrow, rotating beam of at least one ground station remote from said own station and said vehicle transponders, said ground stations omni-directionally transmitting a reference signal as the respective beams thereof sweep through a standardized reference direction, such as magnetic North, said process comprising the steps of:
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(a) receiving said reference signals transmitted by said ground stations; (b) receiving said interrogations transmitted by said ground stations; (c) selecting the reference signal and interrogations received from one of said ground stations; (d) determining the elapsed time between the receipt of said selected reference signal and said selected interrogations for a given beam rotation of said one ground station; (e) determining the angle of incidence of transponder replies, thereby to obtain the bearing of a nearby vehicle transponder and the azimuth of said beam of said one ground station when it is directed at the place of said own station where said interrogatories are received. - View Dependent Claims (47)
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48. Proximity indicating apparatus situated at an "own" station for use in an azimuthally scanning secondary surveillance radar (SSR) system in which at least one transponder situated at an "other" station in the proximity of said own station is interrogated by the narrow rotating beam of at least one ground station remote from said own and said other station, said apparatus comprising, in combination:
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(a) direction-finding antenna means, for receiving transponder replies transmitted by said other transponder station; (b) direction-finding means, connected to said antenna means, for determining the angle of incidence of said transponder replies on said antenna means; (c) first receiver means for detecting interrogations transmitted by a ground station when said beam is directed thereto; (d) means, connected to said first receiver means, for determining the angle of incidence on said own station of interrogations received from one of said ground stations; (e) second receiver means for detecting transponder replies transmitted by said other transponder station; f. timer means connected to said first and said second receiver means, for determining the difference (TD) between the time that an interrogation would be received if the beam of said one ground station were directed at said first receiver means, and the time of receipt of a transponder reply to that interrogation; (g) first logic means, connected to said angle determining means, for determining the angle (D) between the directions of incidence of an interrogation and a transponder reply; (h) second logic means, connected to said first logic means, for determining the value (1 - cos D) of one minus the cosine of said angle (D) between said directions of incidence; and (i) third logic means, connected to said timer means and to said second logic means, for determining the value TD /(1 - cos D) of the quotient of said time difference (TD) divided by said value of one minus the cosine of said angle (D) between said directions of incidence; whereby said quotient is proportional to the slant range from said own station to said other transponder station. - View Dependent Claims (49, 50)
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51. A process for detecting at an "own" station the proximity of mobile, transponder-carrying vehicles in an azimuthally scanning secondary surveillance radar (SSR) system wherein vehicle transponders in the proximity of said own station reply to interrogations transmitted in a narrow, rotating beam of at least one ground station remote from said own station and said vehicle transponders, said process comprising the steps of:
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(a) receiving transponder replies to an interrogation at said own station during a predetermined period following the time that said interrogation would be received if said beam were directed toward said own station; (b) determining the angle of incidence of said transponder replies received during said predetermined period; (c) determining the angle of incidence of interrogations transmitted by a ground station; (d) determining the difference (TD) between the time that an interrogation would be received if the beam of said ground station were directed toward the place of receipt at said own station of said transponder replies and the time of receipt of a transponder reply to that interrogation; and (e) determining the slant range from said own station to said vehicle transponder, without transmission from said own station.
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Specification