Secondary radar/iff anti-target splitting azimuth determiner

Claim 1

A device for use in conjunction with an IFF system which on the basis of replies to interrogations determines and indicates the IFF target leading edge and trailing edge, said IFF system having receiving means for receiving replies to interrogations and for indicating when a reply is correct, said device comprising: counting means connected to said IFF system for counting the number of interrogations made by the IFF system; means, connected to said receiving means and to said counting means, for producing a leading-edge signal when a predetermined number T L of correct replies are received in any consecutive sequence of W L responses; means, connected to said receiving means and to said counting means, for producing a trailing-edge signal upon the occurrence of a number T Z of non-correct replies in a group of W 2 replies and either at least a number B of successive interrogations have been transmitted after a leading-edge signal has been produced, or a number T u of correct replies is found to exist in a group of W u received replies followed by reduction of said number T u to a smaller number T t .

Claim 2

A device for use in conjunction with an IFF system which on the basis of replies to interrogations determines and indicates the IFF target leading edge and trailing edge, said IFF system having receiving means for receiving replies to interrogations and for indicating when a reply is correct, said device comprising: counting means connected to said IFF system for counting the number of interrogations made by the IFF system; means, connected to said receiving means and to said counting means, for producing a leading-edge signal when a predetermined number T L of correct replies are received in any consecutive sequence of W L responses; means, connected to said receiving means and to said counting means, for producing a trailing-edge signal upon the occurrence of a number T Z of non-correct replies in a group of W 2 replies and either at least a number B of successive interrogations have been transmitted after a leading-edge signal has been produced, or a number T u of correct replies is found to exist in a group of W u received replies followed by reduction of said number T u to a smaller number T t .

Claim 3

A method based upon received replies to IFF interrogations, for determining and indicating occurrence of a IFF target leading edge and trailing edge comprising the steps of: counting the number of interrogations; counting the number of correct replies in a sequence W of last responses; counting the number of incorrect replies in a sequence W of last responses; subtracting the number of incorrect replies from the number of correct replies to produce a difference quantity T; indicating that the targets leading edge has occurred if the difference quantity T becomes equal to or greater than a predetermined threshold T L before a predetermined number N of interrogations are counted; indicating that the responding signals constitute a trailing edge when said number of incorrect replies received in a group of W z responses exceeds a predetermined number T z and either a number B of interrogations have occurred after occurrence of said target leading edge indication, or a number T t of correct replies is received after receiving a larger number of T u correct replies in a previous group of replies.

Claim 4

A method based upon received replies to IFF interrogations, for determining and indicating occurrence of a IFF target leading edge and trailing edge comprising the steps of: counting the number of interrogations; counting the number of correct replies in a sequence W of last responses; counting the number of incorrect replies in a sequence W of last responses; subtracting the number of incorrect replies from the number of correct replies to produce a difference quantity T; indicating that the targets leading edge has occurred if the difference quantity T becomes equal to or greater than a predetermined threshold T L before a predetermined number N of interrogations are counted; indicating that the responding signals constitute a trailing edge when said number of incorrect replies received in a group of W z responses exceeds a predetermined number T z and either a number B of interrogations have occurred after occurrence of said target leading edge indication, or a number T t of correct replies is received after receiving a larger number of T u correct replies in a previous group of replies.

Claim 5

A device for use with an IFF system which provides an output (H) for each correct reply reserved in response to its interrogations and an output (I) for each interrogation it sends, the I signal occurring only after all possibility of receiving an H signal is past, said device unambiguously determining and declaring the leading and trailing edges of an IFF target and comprising: leading-edge means, connected to receive said H signal, for determining and declaring the leading edge of an IFF target after a preselected number T L of correct replies in response to a preselected number W L of successive interrogations is received; and trailing-edge means, connected to receive said H and I signals, for determining and declaring the trailing edge of an IFF target when a preselected number T Z of non-correct (incorrect replies and non-replies) replies are received in response to a preselected number W Z of successive interrogations and when either a preselected number T t of correct replies are received in response to a preselected number of successive interrogations after a higher number T u of correct replies in response to the same number of successive interrogations has been received, or when a count of B successive interrogations is reached after a leading edge has been declared.

Claim 6

A device for use with an IFF system which provides an output (H) for each correct reply reserved in response to its interrogations and an output (I) for each interrogation it sends, the I signal occurring only after all possibility of receiving an H signal is past, said device unambiguously determining and declaring the leading and trailing edges of an IFF target and comprising: leading-edge means, connected to receive said H signal, for determining and declaring the leading edge of an IFF target after a preselected number T L of correct replies in response to a preselected number W L of successive interrogations is received; and trailing-edge means, connected to receive said H and I signals, for determining and declaring the trailing edge of an IFF target when a preselected number T Z of non-correct (incorrect replies and non-replies) replies are received in response to a preselected number W Z of successive interrogations and when either a preselected number T t of correct replies are received in response to a preselected number of successive interrogations after a higher number T u of correct replies in response to the same number of successive interrogations has been received, or when a count of B successive interrogations is reached after a leading edge has been declared.