Aircraft traffic alert and collision avoidance device
First Claim
1. In a proximity warning system for a host aircraft which includes a host transponder and a reply detector, said proximity warning system based on evaluation of replies from transponders of other aircraft to interrogations from a Secondary Surveillance Radar, an improved reply detector comprising:
- a) first means for suppressing said host transponder for a succession of suppression durations, wherein a delay between an end of one suppression duration and initiation of an adjacent suppression duration is no greater than about 8.5 ms., and wherein a ratio of the summation of time durations within a succession of suppression durations to a total time span encompassing said succession of suppression durations is in a range of about 13 to 20%,b) a reply receiver,c) data storage means responsive to said first means for storing data from said reply receiver only during a suppression duration, andd) threat evaluation means responsive to said data storage means for signaling presence of a collision threat.
1 Assignment
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Accused Products
Abstract
A passive aircraft Traffic alert and Collision Avoidance device (TCAD) is based on sensing and responding to transponder replies of other aircraft to SSR interrogations. In order to avoid masking other aircraft replies by the host transponder TCAD repeatedly and randomly suppresses the host transponder and simultaneously listens for other aircraft replies. Suppression on each occasion is effective for an equal and predetermined duration which is much longer than a typical reply, in a preferred embodiment the suppression/listen duration is 725 μs. In this embodiment the time between successive suppression/listen occasions is random between 725 μs. and 5.025 ms. with an average value of about 2.9 ms. Digital signal processing is used to detect and discard garbled or overlapping replies. Each valid reply, exhibiting a minimum pulse amplitude, is decoded and correlated with a calibrated range parameter and given a time tag. Successive replies which match to within predetermined criteria in time and calibrated range are merged to track the positional relation between the host and other aircraft. The positional relation between other aircraft and the host are evaluated via a priority table in terms of relative altitude and range to locate that craft which poses the highest threat to the host. Parameters of such a craft are displayed. In the event a craft penetrates a shield of programmable size an audible alert is sounded. TCAD provides for shields for each of a plurality of flight regimes, such as terminal, standard and enroute. Selection among shields is via a single pushbutton. TCAD allows the pilot to program each of the different shield sizes. Peripheral functions such as altitude deviation alert, density altitude and barometric pressure correction for altitude reporting are also provided.
111 Citations
65 Claims
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1. In a proximity warning system for a host aircraft which includes a host transponder and a reply detector, said proximity warning system based on evaluation of replies from transponders of other aircraft to interrogations from a Secondary Surveillance Radar, an improved reply detector comprising:
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a) first means for suppressing said host transponder for a succession of suppression durations, wherein a delay between an end of one suppression duration and initiation of an adjacent suppression duration is no greater than about 8.5 ms., and wherein a ratio of the summation of time durations within a succession of suppression durations to a total time span encompassing said succession of suppression durations is in a range of about 13 to 20%, b) a reply receiver, c) data storage means responsive to said first means for storing data from said reply receiver only during a suppression duration, and d) threat evaluation means responsive to said data storage means for signaling presence of a collision threat. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A proximity warning system for host aircraft based on evaluation of replies from transponder equipped other aircraft to interrogations from a Secondary Surveillance Radar, said system including a host transponder and a reply detector, said reply detector comprising:
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a) first means for repeatedly suppressing said host transponder for a sequence of suppression durations, each of a given, equal, duration whose initiation is selected within a given time window on a random basis, b) a reply receiver, c) data storage means responsive to said first means for storing data from said reply receiver only during a suppression duration, and d) threat evaluation means responsive to said data storage means for signaling presence of a collision threat. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. In a proximity warning system based on receipt, at an own aircraft, of replies by transponders of other aircraft to interrogations from Secondary Surveillance Radar, a method of reducing the masking effect of own aircraft transponder replies comprising the steps of:
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a) dividing time into a succession of time slices of different durations, each time slice including only one suppression duration, remaining time in any time slice available for reply transmissions, b) actively asserting a suppression signal to an own aircraft transponder for the duration of each of said suppression durations, c) disabling receipt of replies outside of a suppression duration, d) wherein each of said suppression durations are selected to last for equal durations, and e) initiating a suppression duration in a time slice at a time within said time slice selected at random. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. In a proximity warning system based on receipt, at an own aircraft, of replies by transponders of other aircraft, a method of threat detection for treating otherwise ambiguous Mode A and Mode C replies comprising the steps of:
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a) establishing a threat altitude region based on own aircraft altitude, b) selecting for treatment as a possible Mode C reply only received data equivalent to a defined Mode C reply, and c) selecting for treatment only a subset of those replies selected in step b), said subset comprising those replies representing an altitude within said threat altitude region. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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52. In a proximity warning system for host aircraft including a transponder and a reply detector and based on evaluation of replies from transponders of other aircraft, a reply detector and altitude alert comprising:
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a) buffer means responsive to altitude measurement for reporting own aircraft altitude, b) reply detecting means responsive to transponder replies from other aircraft for displaying proximate threats based on own aircraft altitude as determined from said buffer means, c) recording means responsive to engaging an altitude alerting function for recording existing own aircraft altitude when said altitude alerting function is engaged, d) comparing means enabled on engaging said altitude alerting function for comparing the own aircraft altitude recorded by said recording means with own aircraft altitude of said buffer means to generate an altitude difference, and e) alarm means responsive to said altitude difference from said comparing means for producing an alarm when said altitude difference is increased above a predetermined altitude difference threshold. - View Dependent Claims (53, 54, 55, 56, 57, 58)
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59. In a proximity warning system for host aircraft including a transponder and a reply detector and based on evaluation of replies from transponders of other aircraft, a reply detector and altimeter check comprising:
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a) buffer means responsive to pressure altitude measurement for reporting own aircraft altitude, b) reply detecting means responsive to transponder replies from other aircraft for displaying information on proximate threats based on own aircraft altitude as determined from said buffer means, c) recording means responsive to engaging a barometric correction function for recording local barometric pressure, and d) altitude display means responsive to said reporting means and to said recording means for compensating the own aircraft altitude from said buffer means in accordance with said local barometric pressure from said recording means to display, local barometric pressure corrected, own aircraft altitude. - View Dependent Claims (60)
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61. In a proximity warning system for host aircraft including a transponder and a reply detector and based on evaluation of replies from transponders of other aircraft, a reply detector and density altitude computer comprising:
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a) buffer means responsive to pressure altitude measurement for reporting own aircraft altitude, b) reply detecting means responsive to transponder replies from other aircraft for displaying information on proximate threats based on own aircraft altitude as determined from said buffer means, c) recording means responsive to engaging a density altitude function for recording local ambient temperature, and d) density altitude display means responsive to said buffer means and to said recording means for compensating the own aircraft altitude from said buffer means in accordance with said local ambient temperature from said recording means to display, local temperature corrected, own aircraft density altitude.
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62. A method of validating a transponder reply in a proximity warning system comprising the steps of:
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a) identifying F1 and F2 reply pulses; b) determining if said pulses differ in amplitude by more than a given amount;
rejecting said reply if they do, otherwise accepting said pulses;c) averaging amplitudes of said F1 and F2 pulses to determine a midpoint; d) identifying a pulse received between said F1 and F2 pulses in time and closest to a current midpoint;
terminating said validation if no pulse is identified;e) rejecting a pulse identified in step d) and terminating the validation if the identified pulse has an amplitude differing by more than a specified amount from said current midpoint, otherwise accepting said pulse; f) determining a new midpoint if the pulse identified in step d) has an amplitude which is greater or less than the amplitudes of the largest or smallest pulse which has been accepted; and g) repeating steps d), e), and f) until said validation is terminated. - View Dependent Claims (63, 64, 65)
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Specification