Aircraft location and collision avoidance system

An aircraft location system which utilizes conventional position determining equipment providing output signals having azimuth and range information with respect to a fixed reference location, said conventional position determining equipment also providing a periodic azimuth synchronization signal, comprising:

• first means for generating a synthetic azimuth function, which function is a time-expanded version of a conventional periodic azimuth function, said generating means including means for generating a periodic synthetic azimuth synchronization signal from the periodic azimuth synchronization signal, said synthetic azimuth function describing an aircraft's azimuth as a time delay with respect to the occurrence of the periodic synthetic azimuth synchronization signal, said first generating means providing an output signal representative of the synthetic azimuth function;
• second means for generating a synthetic range function which describes an aircraft's range as a time delay with respect to the occurrence of one of the conventional periodic azimuth reference signals, said second generating means providing an output signal representative of the synthetic range function;
• means for encoding an aircraft's position in terms of the synthetic azimuth function and in terms of the synthetic range function, said encoding means providing an output signal at a time, measured from the periodic synthetic azimuth synchronization signal, corresponding to the aircraft's position;
• comparator means for comparing the synthetic azimuth function signal to the encoded aircraft azimuth output signal and for comparing the synthetic range function signal to the encoded aircraft range output signal, said comparator providing and output signal indicative of the coincidence of the respective signals being compared so that the location of an aircraft in terms of the synthetic azimuth function and the synthetic range function is obtained.

A location system for an aircraft, comprising:

• a transmitter at a fixed location providing a periodically pulsed synthetic azimuth reference synchronizing signal and also providing a periodically pulsed synthetic range reference synchronizing signal having a period which is a sub-multiple of the period of the synthetic azimuth reference synchronizing signal, said synthetic range reference synchronizing signals providing equal synthetic azimuth degree increments;
• means for providing the azimuth and range information of the aircraft with respect to the transmitter location;
• means for encoding the azimuth of the aircraft with respect to the transmitter location as a synthetic azimuth pulse having a time delay with respect to the synthetic azimuth reference synchronizing signal, which time delay is proportional to the azimuth of the aircraft with respect to the transmitter location;
• means for encoding the range of the aircraft as a synthetic range pulse having a time delay with respect to the synthetic range reference synchronizing signal, which time delay is proportional to the range of the aircraft from the transmitter location;
• means for transmitting an aircraft location signal at a time corresponding to the simultaneous occurrence of the synthetic azimuth pulse and the synthetic range pulse;
• means for receiving said aircraft location signal and for decoding the azimuth information and the range information to obtain the position of the aircraft with respect to the transmitter at the fixed location;
• and
• means for displaying the position of the aircraft relative to the transmitter location.

A method for providing information about the location of an aircraft, comprising the steps of:

• generating a first synthetic function which is a transformed version of a first conventional function and which describes one coordinate of the aircraft's position;
• synchronizing the first synthetic function with a first synchronizing pulse derived from signals from the first conventional function;
• generating a second synthetic function which describes another coordinate of the aircraft's position;
• synchronously starting and stopping the second synthetic function within the time required for a predetermined degree change in the first synthetic function by synchronizing the second synthetic function with pulses which are derived from signals from the first conventional function;
• and
• transmitting a pulse at a time when the value of the first synthetic function and the second synthetic function corresponds to the coordinates of the aircraft's position.

A method of air collision avoidance, comprising the steps of:

• time encoding azimuth information by generating a synthetic azimuth function which expands the time period for a conventional azimuth function from 1/30th of a second to a greater number of seconds, azimuth information being encoded as a time delay with respect to a synthetic reference azimuth synchronizing pulse which occurs once for every 360 conventional azimuth synchronizing pulses;
• encoding range information by generating a synthetic range function which makes range information proportionate to a time delay with respect to the most recently occurring azimuth synchronizing pulse;
• and
• transmitting a signal from an aircraft, the time of which signal, measured from the occurrence of the synchronizing pulses of the synthetic azimuth and range functions, respectively, is indicative of the aircraft's position in terms of the synthetic azimuth and range functions.

A method for enabling a parent aircraft to determine the location of a target aircraft, comprising the steps of:

• generating a synthetic azimuth function, which function is a time-expanded version of a periodic azimuth function describing an aircraft's azimuth as a time-delay with respect to the occurrence of an azimuth synchronizing signal;
• generating a synthetic range function, which function describes an aircraft's range as a time-delay with respect to the occurrence of a range synchronizing signal;
• providing the target aircraft with a signal representative of its azimuth with respect to a reference location and providing the target aircraft with a signal representative of its range with respect to the reference location;
• transmitting an output signal at a time when the target aircraft's representative azimuth and range signals correspond to the synthetic azimuth and synthetic range functions, respectively;
• and
• comparing the transmitted output signal to the synthetic azimuth function and to the synthetic range function to provide an output signal indicative of the location of the target aircraft.

A method for providing the location of an aircraft, comprising the steps of:

• providing a transmitter at a fixed location which transmits a periodically pulsed synthetic azimuth reference synchronizing signal;
• providing a periodically pulsed synthetic range reference synchronizing signal having a period which is an integer submultiple of the period of the synthetic azimuth reference synchronizing signal to provide equal synthetic azimuth degree increments;
• providing azimuth and range information of the aircraft with respect to the transmitter location;
• encoding the azimuth of the aircraft with respect to the transmitter location as a synthetic azimuth pulse having a time delay with respect to the synthetic azimuth reference synchronizing signal so that the time delay is proportional to the azimuth of the aircraft;
• encoding the range of the aircraft as a synthetic range pulse having a time delay with respect to one of the synchronizing range reference synchronizing signals so that the time delay is proportional to the range of the aircraft from the transmitter location;
• transmitting an aircraft location signal at a time corresponding to the simultaneous occurrence of the synthetic azimuth pulse and the synthetic range pulse;
• receiving the aircraft location signal and decoding the azimuth information and the range information to obtain the position of the aircraft with respect to the transmitter at the fixed location;
• and
• displaying the position of the aircraft.