Improvements in code validation algorithms for secondary surveillance radar

Provides optimization criteria for the algorithms used in secondary surveillance radars (SSR) in order to detect and validate the correct code of the aircraft replying to MARK XII interrogations (code validation algorithms). Code validation algorithms are used to minimize probability of incorrect plot code extraction. A wide variety of techniques have been developed all based on the use of the code and confidence information. All these algorithms are different in the number of consecutive replies to be taken in account for code validation (i.e. single, double and triple confidence). Algorithms based on higher order of confidence (double or more) decrease the number of wrong validated codes, and affect, at the same time, the probability of correct code validation. This consideration makes useful to have a variable threshold for code validation that can be tuned in the different environmental conditions and radar characteristics