Synchronizing techniques for an aircraft collision avoidance system

• US 3,882,497 A
• Filed: 07/02/1973
• Issued: 05/06/1975
• Est. Priority Date: 07/02/1973
• Status: Expired due to Term

• Current Assignee: Charles P. Harman Jr, Philip J. Klass
• Original Assignee: Charles P. Harman Jr, Philip J. Klass
• Inventors: Klass, Philip J., Harman, Charles P. Jr.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/375,631
• Time in Patent Office: 673 Days
• Field of Search: 343/6R,6.5R,6.5LC,112CA
• US Class Current: 342/32
• CPC Class Codes: G01S 13/781 Secondary Surveillance Radar [SSR] in general
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft

Abstract

A system for avoiding collision between a group of aircraft within range of a ground-controlled radar beam that is cyclically moved so that the beam sequentially strikes the aircraft. Identical radio transmitting and receiving equipment is carried on each aircraft. The equipment is arranged so that an aircraft transmits an interrogating signal only upon receipt of the leading edge of the radar beam, but responds to an interrogating signal at any time. By synchronizing the transmission of interrogating signals with the radar beam, the collision avoidance information transmitted between the airplanes within range of the radar beam is sequenced in an orderly fashion to avoid confusion between the signals.

Claims

1. Apparatus for avoiding collision between a first aircraft and a second aircraft located within the range of a ground controlled radar beam that is cyclically moved through a predetermined arc so that the beam periodically strikes the first and second aircraft comprising:

a secondary radar transponder located on the first aircraft for generating a first start signal in response to the receipt of the radar beam;

means located on the first aircraft for transmitting a first interrogating signal to the second aircraft in response to the first start signal, for receiving a first response signal from the second aircraft and for transmitting a second response signal in response to a second interrogating signal received from the second aircraft, said means comprising a pulse generator for generating pulses, a modulator for modulating the pulses, a transmitter for transmitting the modulated pulses at radio frequency, and electronic logic means for interconnecting the pulse generator to the modulator in response to the start signal, said electronic logic means including means for enabling the transmitting of the first interrogating signal for a first predetermined time period and for thereafter preventing the transmitting of the first interrogating signal for a second predetermined time period;

means located on the second aircraft for transmitting the first response signal in response to the first interrogating signal received from the first aircraft, for generating a second start signal in response to the receipt of the radar beam, for transmitting the second interrogating signal to the first aircraft in response to the second start signal and for receiving the second response signal;

means located on the first aircraft for processing information derived from the first interrogating signal and the first response signal to determine the relative location of the first and second aircraft; and

means located on the second aircraft for processing information derived from the second interrogating signal and the second response signal to determine the relative location of the first and second aircraft, whereby the transmission of interrogating signals by the first and second aircraft is sequenced and synchronized by the movement of the radar beam.

2. In a system for avoiding collision between a group of aircraft within range of a ground-controlled beam of electromagnetic radiation that is cyclically moved through a predetermined arc so that the beam periodically strikes the aircraft, improved apparatus carried on one of the aircraft in the group and adapted to cooperate with like apparatus carried on other aircraft in the group comprising in combination:

a secondary radar transponder for generating a start signal in response to the receipt of the beam;

means for transmitting an interrogating signal to the oTher aircraft in response to the start signal, for receiving response signals transmitted by the other aircraft in response to the interrogating signal and for transmitting a response signal in response to the receipt of each interrogating signal transmitted by the other aircraft, said means comprising a pulse generator for generating pulses, a modulator for modulating the pulses, a transmitter for transmitting the modulated pulses at radio frequency, and electronic logic means for interconnecting the pulse generator to the modulator in response to the start signal, said electronic logic means including means for enabling the transmitting of the interrogating signal from the one aircraft for a first predetermined time period and for thereafter preventing the transmitting of the interrogating signal from the one aircraft for a second predetermined time period; and

means for processing information derived from the interrogating signal and the response signals to determine the relative positions of the one aircraft and the other aircraft.

3. A method for avoiding collision between a first aircraft and a second aircraft located within the range of a ground controlled radar beam that is cyclically moved through a predetermined arc so that the beam periodically strikes the first and second aircraft, said method comprising the steps of:

generating a first start signal aboard the first aircraft in response to the receipt of the radar beam;

transmitting a first interrogating signal from the first aircraft to the second aircraft in response to the first start signal;

preventing the transmitting of an interrogating signal aboard the first aircraft for a predetermined time period following the termination of the first interrogating signal;

receiving the first interrogating signal aboard the second aircraft;

transmitting a first response signal from the second aircraft to the first aircraft in response to the first interrogating signal;

receiving the first response signal aboard the first aircraft;

processing information derived from the first interrogating signal and the first response signal aboard the first aircraft to determine the relative position of the first and second aircraft;

generating a second start signal aboard the second aircraft in response to the receipt of the radar beam;

transmitting a second interrogating signal from the second aircraft to the first aircraft in response to the second start signal;

preventing the transmitting of an interrogating signal aboard the second aircraft for a predetermined time period following the termination of the second interrogating signal;

receiving the second interrogating signal aboard the first aircraft;

transmitting a second response signal from the first aircraft to the second aircraft in response to the second interrogating signal;

receiving the second response signal aboard the second aircraft; and

processing information derived from the second interrogating signal and the second response signal aboard the second aircraft to determine the relative position of the first and second aircraft, whereby the transmission of the interrogating signals by the first and second aircraft is sequenced and synchronized by the movement of the radar beam.

4. Apparatus for avoiding collision between a first aircraft and a second aircraft located within the range of a ground controlled radar beam that is cyclically moved through a predetermined arc so that the beam periodically strikes the first and second aircraft comprising:

means located on the first aircraft for generating a first start signal in response to the receipt of the radar beam;

means located on the first aircraft for transmitting a first interrogating signal to the second aircraft in response to the first start signal, for receiving a first response signal from the second aircraft and for transmitting a second response signal in response to a second interrogating signal received from the second aircraft;

first delay means for delaying the transmitting of the first interrogating signal from the first aircraft to the second aircraft for a first predetermined time period;

means located on the second aircraft for transmitting the first response signal in response to the first interrogating signal received from the first aircraft, for generating a second start signal in response to the receipt of the radar beam, for transmitting the second interrogating signal to the first aircraft in response to the second start signal and for receiving the second response signal;

second delay means for delaying the transmitting of the second interrogating signal from the second aircraft to the first aircraft for a second predetermined time period different from the first predetermined time period;

means located on the first aircraft for processing information derived from the first interrogating signal and the first response signal to determine the relative location of the first and second aircraft; and

means located on the second aircraft for processing information derived from the second interrogating signal and the second response signal to determine the relative location of the first and second aircraft, whereby the transmission of interrogating signals by the first and second aircraft is sequenced and synchronized by the movement of the radar beam.

5. In a system for avoiding collision between a group of aircraft within range of a ground-controlled beam of electromagnetic radiation that is cyclically moved through a predetermined arc so that the beam periodically strikes the aircraft, improved apparatus carried on one of the aircraft in the group and adapted to cooperate with like apparatus carried on other aircraft in the group comprising in combination:

means for generating a start signal in response to the receipt of the beam;

means for transmitting an interrogating signal to the other aircraft in response to the start signal, for receiving response signals transmitted by the other aircraft in response to the interrogating signal and for transmitting a response signal in response to the receipt of each interrogating signal transmitted by the other aircraft;

delay means for delaying the transmitting of the interrogating signal to the other aircraft for an adjustable time period; and

means for processing information derived from the interrogating signal and the response signals received from the other aircraft to determine the relative positions of the one aircraft and the other aircraft.

6. A method for avoiding collision between a first aircraft and a second aircraft located within the range of a ground controlled radar beam that is cyclically moved through a predetermined arc so that the beam periodically strikes the first and second aircraft, said method comprising the steps of:

generating a first start signal aboard the first aircraft in response to the receipt of the radar beam;

transmitting a first interrogating signal from the first aircraft to the second aircraft in response to the first start signal after waiting for a first predetermined time period;

receiving the first interrogating signal aboard the second aircraft;

transmitting a first response signal from the second aircraft to the first aircraft in response to the first interrogating signal;

receiving the first response signal aboard the first aircraft;

processing information derived from the first interrogating signal and the first response signal aboard the first aircraft to determine the relative position of the first and second aircraft;

generating a second start signal aboard the second aircraft in response to the receipt of the radar beam;

transmitting a second interrogating signal from the second aircraft to the first aircraft in response to the second start signal after waiting for a second predetermined time period different from the first predetermined time period;

receiving the second interrogAting signal aboard the first aircraft;

transmitting a second response signal from the first aircraft to the second aircraft in response to the second interrogating signal;

receiving the second response signal aboard the second aircraft; and

processing information derived from the second interrogating signal and the second response signal aboard the second aircraft to determine the relative position of the first and second aircraft, whereby the transmission of the interrogating signals by the first and second aircraft is sequenced and synchronized by the movement of the radar beam.