Proximity indication with range and bearing measurements

Claim 3

The method according to claim 1 comprising the further step of: h. limiting the production of the second representation to the occurrence of reply signals from transponder stations within a common azimuthal sector with said own transponder station.

Claim 4

The method according to claim 1 wherein step (d) comprises measuring the time interval between successive receptions of said selected reference signals to produce the quantitative first representation.

Claim 5

Apparatus for determining at an own transponder station the bearing angle phi '' of another transponder station from a selected one of a plurality of secondary surveillance radars (SSR) that transmit directional interrogation signals of the same frequency and that omniazimuthally transmit reference signals as the main radar beams thereof sweep through a standardized reference direction, such as magnetic North, said apparatus comprising: a. means for receiving said reference signals from said radars, b. means for selecting the reference signals received from one of said secondary surveillance radars, c. means for receiving reply signals transmitted by said other transponder station in response to interrogation signals from said selected radar as the main beam thereof sweeps by said other transponder station, d. means for measuring the rotational period of the main beam of the selected radar and producing a quantitative first representation of the main beam rotation period, e. means for measuring and producing a quantitative second representation of the time interval between reception of one of said selected reference signals and said reply signal and the next subsequently received other one of said signals, f. divider means for dividing the value of the second representation by that of the first representation to produce the quotient of said values, and g. means for producing a quantitative representation phi '' of said quotient.

Claim 6

Apparatus for determining at an own transponder station the bearing angle phi '' of another transponder station from a selected one of a plurality of secondary surveillance radars (SSR) that transmit directional interrogation signals of the same frequency and that omniazimuthally transmit reference signals as the main radar beams thereof sweep through a standardized reference direction, such as magnetic North, said apparatus comprising: a. means for receiving said reference signals from said radars, b. means for selecting the reference signals received from one of said secondary surveillance radars, c. means for receiving reply signals transmitted by said other transponder station in response to interrogation signals from said selected radar as the main beam thereof sweeps by said other transponder station, d. means for measuring the rotational period of the main beam of the selected radar and producing a quantitative first representation of the main beam rotation period, e. means for measuring and producing a quantitative second representation of the time interval between reception of one of said selected reference signals and said reply signal and the next subsequently received other one of said signals, f. divider means for dividing the value of the second representation by that of the first representation to produce the quotient of said values, and g. means for producing a quantitative representation phi '' of said quotient.

Claim 7

Apparatus according to claim 4 further comprising: h. means for limiting the production of the second representation to the occurrence of reply signals from transponder stations within a common azimuthal sector with said own transponder station.

Claim 8

Apparatus according to claim 4 wherein the first interval timer measures the interval between successive receptions of said selected reference signals and produces a quantitative representation N of the main radar beam rotational period.