Proximity indication with range and bearing measurements

Claim 3

The method according to claim 1 comprising the further steps of: h. producing at the own transponder station a reference signal having a predetermined time relation with respect to the interrogations received by the own transponder from said SSR, i. producing a range warning signal in response to the reception of a corresponding reply from another''s transponder within a predetermined time interval following said reference signal, and j. producing said raNge command signal only in response to the simultaneous occurrence of said common azimuth sector signal and said range warning signal whereby replies of transponders occurring outside said common azimuth sector and said predetermined time interval are ignored.

Claim 4

Apparatus for determining slant range Y between an own and another transponder station that are in different directions from a secondary surveillance radar (SSR) such that they are interrogated successively as the main beam of the radar sweeps by them in succession, comprising: a. receiver means for receiving the other''s transponder replies at the own transponder station, b. means for establishing from said replies the other''s dwell time as the SSR beam sweeps by the other station, c. means for establishing own''s dwell time from the interrogations received by the own transponder as the SSR beam sweeps by the position of the own station, d. means for producing at the own station a common azimuth sector signal in response to occurrence of both of said dwell times within an interval that corresponds to the width of a predetermined common azimuth sector from the SSR, e. means for producing at the own station a range command signal in response to said common azimuth sector signal, whereby replies of transponders occurring outside said common azimuth sector are ignored, f. means for transmitting said range common signal from the own station to the other transponder station, and g. means for measuring and producing at the own station a quantitative representation Y of the time interval between said range command transmission and the reply received from the other''s transponder in response thereto.

Claim 5

Apparatus for determining slant range Y between an own and another transponder station that are in different directions from a secondary surveillance radar (SSR) such that they are interrogated successively as the main beam of the radar sweeps by them in succession, comprising: a. receiver means for receiving the other''s transponder replies at the own transponder station, b. means for establishing from said replies the other''s dwell time as the SSR beam sweeps by the other station, c. means for establishing own''s dwell time from the interrogations received by the own transponder as the SSR beam sweeps by the position of the own station, d. means for producing at the own station a common azimuth sector signal in response to occurrence of both of said dwell times within an interval that corresponds to the width of a predetermined common azimuth sector from the SSR, e. means for producing at the own station a range command signal in response to said common azimuth sector signal, whereby replies of transponders occurring outside said common azimuth sector are ignored, f. means for transmitting said range common signal from the own station to the other transponder station, and g. means for measuring and producing at the own station a quantitative representation Y of the time interval between said range command transmission and the reply received from the other''s transponder in response thereto.

Claim 6

Apparatus according to claim 3 further comprising: h. means for producing at the own transponder station a reference signal having a predetermined time relation with respect to the interrogations received by the own transponder from said SSR, i. means for producing a range warning signal in response to the reception of a corresponding reply from another''s transponder within a predetermined time interval following said reference signal, and j. means for producing said range command signal only in response to the simultaneous occurrence of said common azimuth sector signal and said range warning signal whereby replies of transponders occurring outside said common azimuth sector and said predetermined time interval are ignored.

Claim 7

Apparatus for determining the slant range Y between an own transponder and another similarly equipped transponder comprising: a. means for encoding a transmitter at the own transponder to transmit a range command signal, b. means responsive to signals received by the own transponder from a selected secondary surveillance radar (SSR) to produce synthetic pulses representative of the pulse repetition characteristics of said SSR, each pulse having a predetermined time relation with respect to one of the own''s transponder reply pulses when the latter occur, c. means for receiving the other transponder''s transmissions, d. means for measuring the time interval between a said synthetic pulse and the reception of a corresponding reply from another''s transponder to produce a quantitative representation of Y + X thereof, e. algebraic subtractor means for producing a quantitative representation X of the difference between Y + X and Y, f. divider means for producing a quantitative representation of the quotient X/Y, and g. a function generator for producing a quantitative representation theta of the function cos 1 X/Y.

Claim 8

Apparatus for determining the slant range Y between an own transponder and another similarly equipped transponder comprising: a. means for encoding a transmitter at the own transponder to transmit a range command signal, b. means responsive to signals received by the own transponder from a selected secondary surveillance radar (SSR) to produce synthetic pulses representative of the pulse repetition characteristics of said SSR, each pulse having a predetermined time relation with respect to one of the own''s transponder reply pulses when the latter occur, c. means for receiving the other transponder''s transmissions, d. means for measuring the time interval between a said synthetic pulse and the reception of a corresponding reply from another''s transponder to produce a quantitative representation of Y + X thereof, e. algebraic subtractor means for producing a quantitative representation X of the difference between Y + X and Y, f. divider means for producing a quantitative representation of the quotient X/Y, and g. a function generator for producing a quantitative representation theta of the function cos 1 X/Y.

Claim 11

Apparatus for determining the slant range Y between an own transponder and another similary equipped station, comprising: a. means for receiving the transmission from another transponder, b. means for encoding the own transponder to transmit a proximity message signal superimposed on its normal reply message format in response to a received SSR interrogation when a reply messsage is received from another transponder which is within the own''s proximity detection region, c. means for triggering the own transponder to transmit a reply in response to a proximity message signal received from another transponder only while that other transponder is within the own''s proximity detection region, and d. means for measuring the time interval between an own transponder transmission of a proximity message signal and the reply of another transponder received in response thereto.

Claim 12

Apparatus for determining the slant range Y between an own transponder and another similary equipped station, comprising: a. means for receiving the transmission from another transponder, b. means for encoding the own transponder to transmit a proximity message signal superimposed on its normal reply message format in response to a received SSR interrogation when a reply messsage is received from another transponder which is within the own''s proximity detection region, c. means for triggering the own transponder to transmit a reply in response to a proximity message signal received from another transponder only while that other transponder is within the own''s proximity detection region, and d. means for measuring the time interval between an own transponder transmission of a proximity message signal and the reply of another transponder received in response thereto.