WARNING INDICATOR TO ALERT AIRCRAFT PILOT TO PRESENCE AND BEARING OF OTHER AIRCRAFT

• US 3,792,472 A
• Filed: 08/14/1972
• Issued: 02/12/1974
• Est. Priority Date: 08/14/1972
• Status: Expired due to Term

• Current Assignee: Delmar V. Payne, Wilfried G. Jaeckle
• Original Assignee: Delmar V. Payne, Wilfried G. Jaeckle
• Inventors: Payne, Delmar V., Jaeckle, Wilfried G.
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US05/280,308
• Time in Patent Office: 547 Days
• Field of Search: 343/6.5R,6.5LC,112CA
• US Class Current: 342/32
• CPC Class Codes: G01S 3/02 using radio waves
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G08G 5/0008 with other aircraft
• CPC Class Codes: G08G 5/0052 for cruising combined instruments indicating more than one navigational value G01C23/00
• CPC Class Codes: G08G 5/0078 for monitoring traffic from the aircraft radar or analogous systems specially adapted for traffic control G01S13/91

Abstract

A pilot warning indicator which operates in cooperation with the ATCRBS to produce an indication of the presence and bearing of other aircraft at substantially the same altitude as the equipped craft. A spiral-phase field antenna array together with a digital phase comparator utilizes transponder reply signals from other aircraft to ground interrogations to provide bearing indications. Amplitude comparisons are made between transponder reply signals received by omni-directional antennas mounted on the top and bottom of the aircraft fuselage to eliminate warnings of aircraft flying at substantially different altitude than equipped craft.

Claims

1. A pilot warning indicator installed in a first aircraft for alerting the pilot thereof to the presence of other aircraft at substantially the altitude of said first aircraft and for indicating the relative bearing to such other aircraft, said other aircraft being equipped with transponders for replying to interrogation signals, comprising:

a receiver having first, second and third antenna means for receiving transponder reply signals from said other aircraft;

said third antenna means including an array of antennas and feed means therefor whereby signals from said third antenna means vary in phase according to the bearing of said other aircraft relative to said first aircraft;

means for combining signals from said first and second antenna means so as to accept and further process said reply signals from other aircraft located within a limited space above and below the pitch plane of said first aircraft and to reject said replay signals from other aircraft located outside said limited space;

means for comparing the phase of signals accepted by said combining means with corresponding signals received by said third antenna means to provide information of the bearing of said other aircraft within said limited space relative to said first aircraft; and

, means for displaying said bearing information to the pilot thereby directing his attention to a region in space containing said other aircraft.

2. An indicator as claimed in claim 1 wherein said first and second antenna means have substantially equal sensitivity to signals from said other aircraft located on the pitch plane of said first aircraft at any relative bearing thereto and with the sensitivity to signals from said other aircraft located above the pitch plane of said first aircraft being greater for said first antenna means than said second antenna means and being greater for said second antenna means than said first antenna means to signals from said other aircraft located below said pitch plane.

3. An indicator as claimed in claim 2 wherein said combining means includes means for obtaining the difference between logarithms of signals from said first antenna means and said second antenna means;

and means for rejecting said reply signals whenever said difference exceeds a predetermined limit.

4. An indicator as claimed in claim 1 wherein said phase comparing means includes means for delaying incrementally signals received by said first antenna means and said signals received by said third antenna means whereby the bearing of said other aircraft is determined by the relative amount of delay necessary to bring said delayed signals substantially into phase with one another.

5. An indicator as claimed in claim 4 wherein said incremental delay means comprises a delAy line tapped along its length with signals from said first antenna means applied to one end of said delay line and with signals from said third antenna means applied to the opposite end of said delay line.

6. An indicator as claimed in claim 5 including means for comparing the amplitude of signals appearing at adjacent taps of said delay line to provide an output in logic form indicative of the bearing of said other aircraft and further including logic means for controlling said display means in accordance with said logic output.

7. A pilot warning indicator installed in a first aircraft equipped with a transponder for replying to interrogation signals for alerting the pilot thereof to the presence of other aircraft likewise equipped with transponders and for inidcating the relative bearing to such other aircraft, comprising first and second antenna means for receiving transponder reply signals from other aircraft, said first and second antenna means being of substantially equal sensitivity to reply signals from other aircraft located near the pitch plane of said first aircraft and at any relative bearing thereto, said first antenna means being of greater sensitivity to reply signals from other aircraft located above the pitch plane of said first aircraft than to reply signals from other aircraft located below the pitch plane of said first aircraft, the sensitivty of said second antenna means being oppositely directed to provide greater sensitivity to reply signals from other aircraft located below the pitch plane of said first aircraft;

means for comparing reply signals simultaneously received by said first and second antenna means for rejecting reply signals from other aircraft located substantially above or below the pitch plane of said first aircraft and for accepting for further processing reply signals from other aircraft located near to or on the pitch plane of said first aircraft and at any bearing relative to said first aircraft;

third antenna means for receiving reply signals from other aircraft and providing information in the form of signal phase of the bearing relative to said first aircraft of other aircraft from which said reply signals are received;

means for comparing the phase of signals from said third antenna means with signals from said first antenna means to extract said bearing information therefrom;

means for displaying said bearing information only as to other aircraft from which reply signals are accepted by said comparing means; and

, means operative after reception of a fixed member of interrogation signals by the transponder on said first aircraft for preventing for a fixed period replies to valid interrogations by said transponder on said first aircraft whereby said indicator may receive and display reply signals from other aircraft during a time when said transponder on said first aircraft is being interrogated.

8. An indicator as claimed in claim 7 wherein said means for preventing replies for a fixed period includes means for counting interrogation signals received by the transponder on said first aircraft, said preventing means operating to prevent replies only after the accumulation of a fixed count by said counting means.

9. An indicator as claimed in claim 8, with additionally, means for introducing a fixed delay following accumulation of said fixed count before operation of said preventing means, the amount of said delay being of the order of one-half of the normal repetition period of interrogation signals.

10. An indicator as claimed in claim 9 wherein said third antenna means comprises a spiral-phase field array antenna.

11. An indicator as claimed in claim 10 wherein said array antenna comprises, an array of antenna elements;

feed means for said array; and

phase shifters in said feed means for introducing a phase shift to each element of said array which progressively increases by a fixed amount for each successive element of said array.

12. An indicator as claimed in claim 11 wherein said phase comparing means comprises a tapped delay line with signals from said array antenna applied to one end thereof and signals from said first antenna means applied to the opposite end thereof, said phase comparing means further including means for comparing the amplitude of signals simultaneously appearing at adjacent taps of said delay line to provide outputs in the form of unique logic sets identifying sectors of relative bearing containing the other aircraft from which reply signals are received by said array antenna and said first antenna means.

13. An indicator as claimed in claim 12, with additionally, counting means interposed between said phase comparing means and said display means to inhibit display of bearing information until after a fixed number of coincident bearing information signals has been accumulated.

14. An indicator as claimed in claim 13 wherein said means for comparing reply signals received by said first and second antenna means controls said counting means so as to prevent accumulation of a count for a bearing information signal corresponding a reply signal rejected by said first and second antenna comparing means.

15. A pilot warning indicator installed in a first aircraft for alerting the pilot thereof to the presence and relative bearing of other aircraft flying at nearly the same altitude as the first aircraft, said first aircraft and said other aircraft being equipped with transponders for replying to interrogation signals, comprising first and second antennas for receiving transponder reply signals from other aircraft, said first and second antennas having substantially equal omnidirectional gain patterns on the pitch plane of said first aircraft, the gain patterns of said first and second antennas being greater, respectively, above and below the pitch plane of said first aircraft;

an antenna array for receiving transponder reply signals from other aircraft said array having spiral-phase field characteristics whereby the signal produced at the output thereof varies in phase with reference to the free field signal producing such output substantially directly according to the azimuth bearing of the source of such free field signal from said array;

a local oscillator;

means for mixing coherently signals from said first, second and array antennas with output from said local oscillator to produce three separate intermediate frequency signals;

means for obtaining the logarithms of said intermediate frequency signals originating at said first and second antennas;

means for obtaining the difference between said logarithms;

means for comparing the absolute value of said difference with a reference to produce an enabling signal whenever said absolute value is less than said reference;

means for comparing the phase of said intermediate frequency signal originating with said antenna array with the phase of one of said other intermediate frequency signals, said phase comparing means producing an output in digital form related to the bearing of the source of signals received by said first, second and array antennas; and

means controlled by said enabling signal for visually displaying said digital output signals of said phase comparing means.

16. An indicator as claimed in claim 15 and wherein means are provided for preventing operation of said indicator whenever the transponder on said first aircraft replies to an interrogation signal and with additionally, means for counting the number of interrogation signals received by the transponder on said first aircraft;

and means enabling for a fixed period said indicator and preventing reply to interrogation signals after a fixed number of interrogation signals received by the transponder on said first aircraft has been counted.

17. An indicator as claimed in claim 16 with additionally means for inhibiting operation of said indicator enabling means for a second fixed period whereby said indicator is operative only a fRactional part of the time during which the transponder on said first aircraft may reply to interrogation signals.

18. An indicator as claimed in claim 16 wherein said phase comparing means comprises a tapped delay line having said intermediate frequency signal from said array applied to one end thereof and said other intermediate frequency signal applied to the other end thereof, voltage comparators for comparing the voltage between adjacent taps of said delay line and producing digital outputs indicative of the tap of said delay line having the greatest comparative output, and logic gates for assembling digital outputs from said comparators in order to produce a set of signals for actuating said visual display means.

19. An indicator as claimed in claim 18 wherein said visual display means comprises a plurality of signal lamps each disposed to indicate a particular bearing sector relative to said first aircraft, said lamps being actuable by signals from the set produced by said logic gates to become illuminated and identify the bearing sector containing the other aircraft from which reply signals are received.

20. An indicator as claimed in claim 19 with additionally means for counting each signal of said set of signals from said logic gates to prevent illumination of a signal lamp of said display until after a fixed number of signals for actuating that lamp have been counted.