Method for detecting conflicts in the II/SI identification code of a mode S radar with nearby radars, and secondary radar implementing such a method

A method for detecting conflicts in the II/SI identification code of radars nearby a first radar, being a secondary mode-S radar, comprising:

• a first step wherein:
• a coverage of said first radar is extended to obtain synchronized replies in an extended radar coverage;
• said first radar detects unsolicited unsynchronized replies, named fruits, in a region of extended radar coverage;
• the fruits are associated with mode-S targets of said extended radar coverage, one or more positions of said fruits being determined by interpolation with synchronized detections of said targets, on the basis of a mode-S address of said targets;
• a second step wherein said first radar detects a conflict in II/SI code by analyzing geographic regions of radar coverage common to said first radar and to at least one nearby second radar, a conflict being detected if said first radar:
• detects, in sub-regions of an extended radar coverage region, a presence of a first set of fruits of same II/SI code as said first radar, having as source said nearby second radar;
• observes the absence of one or more of said first set of fruits caused by said nearby second radar in a non-overlapping region of radar coverage, being a region of coverage of said first radar which does not overlap with a region of radar coverage of said nearby second radar;
• an overlapping region of radar coverage, which is an overlap in a radar coverage of said first radar and a radar coverage of said nearby second radar forming a region of conflict in II/SI code;
• a third step wherein said first radar detects targets locked by said nearby second radar in said region of conflict on the basis of detection of one or more of a second set of fruits caused by said nearby second radar in said region of conflict, indicating the presence of a target in said region of conflict;
• targets being pre-located in an azimuthal region inside said region of conflict by exploiting an absolute value of a time difference between each of the second set of fruits of said targets due to said nearby second radar and each of the first set of fruits of other targets of said region of extended radar coverage that are caused by said nearby second radar, an azimuthal position of each of said other targets being known.