METHOD AND MEANS FOR OPERATING AN AIRBORNE SWITCHED ARRAY RADAR SYSTEM

• US 3,858,206 A
• Filed: 02/05/1973
• Issued: 12/31/1974
• Est. Priority Date: 02/05/1973
• Status: Expired due to Term

• Current Assignee: Donald L. King, Gerald M. Goldberg, Richard A. Gebhardt, Richard Sidlo, Stuart P. Scheidler
• Original Assignee: Donald L. King, Gerald M. Goldberg, Richard A. Gebhardt, Richard Sidlo, Stuart P. Scheidler
• Inventors: Scheidler, Stuart P., Goldberg, Gerald M., Sidlo, Richard, King, Donald L., Gebhardt, Richard A.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/329,765
• Time in Patent Office: 694 Days
• Field of Search: 343/5DP,7A
• US Class Current: 342/83
• CPC Class Codes: G01S 13/106 using transmission of pulses having some particular characteristics G01S13/12, G01S13/22, G01S13/24, G01S13/26, G01S13/28 and G01S13/30 take precedence
• CPC Class Codes: G01S 13/12 wherein the pulse-recurrence frequency is varied to provide a desired time relationship between the transmission of a pulse and the receipt of the echo of a preceding pulse
• CPC Class Codes: G01S 13/524 based upon the phase or frequency shift resulting from movement of objects, with reference to the transmitted signals, e.g. coherent MTi
• CPC Class Codes: G01S 13/528 with elimination of blind speeds
• CPC Class Codes: G01S 13/66 Radar-tracking systems; Analogous systems
• CPC Class Codes: G01S 13/70 for range tracking only
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/872 Combinations of primary radar and secondary radar
• CPC Class Codes: H01Q 1/28 Adaptation for use in or on aircraft, missiles, satellites, or balloons
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00

Abstract

An airborne radar system is disclosed utilizing multiple fixed antenna arrays mounted within the periphery of the aircraft to avoid aerodynamic modifications and optimumly placed to achieve 360* surveillance coverage. The arrays preferably include a fore mounted array, an aft mounted array, a port mounted array and a starboard mounted array for respectively firing beams in different azimuth sectors relative to the aircraft. Each array is comprised of dipole elements having phase shifters coupled thereto for steering a beam within the corresponding sector. The primary radar antennas time share an exciter, transmitter, receiver and signal processor through switching devices. Time allocation between antennas and between operational modes such as '"'"''"'"''"'"''"'"'search'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'track'"'"''"'"''"'"''"'"' is based on various factors such as mission objectives, current target characteristics and radar purpose. Time allocation is preferably determined by an '"'"''"'"''"'"''"'"'on line'"'"''"'"''"'"''"'"' stored program digital computer which generates a radar control command to define the parameters for each beam to be fired. This procedure involves calculating the priority value of each track and search beam to be fired in accordance with predetermined criteria contained in the stored program. The priority value of each track beam to be fired involves determining the update rate for that target which is calculated based on the characteristics of the target. Priority values are then determined based on a comparison between the elapsed time since the last update and the calculated update rate.

Claims

1. In an airborne radar system including a plurality of fixed beam steered antenna structures mounted in an aircraft, each directed at different sectors within a 360* azimuth volume, control means carried by said aircraft for energizing said antenna structures, said control means comprising:

digital logic means for producing digital signals constituting a radar control command comprised of various information fields respectively specifying (1) an azimuth position within said azimuth volume and (2) either a track or search beam mode, said digital logic means producing successive radar control commands each specifying said search beam mode and successive azimuth positions within said azimuth volume, and said digital logic means further producing radar control commands each specifying said track beam mode and an azimuth position within said azimuth volume;

said digital logic means further including priority means for determining the priorities of the radar control commands to be next produced by said search command means and said track command means;

means for enabling either said search command means or said track command means dependent on the relative value of said priorities to issue an active radar control command; and

transmitter means responsive to said active radar control command for supplying signal energy characteristic of the specified mode to the antenna structure corresponding to the specified azimuth sector.

2. The system of claim 1 including:

receiver means connected to said antenna structures for accepting signal energy reflected from targets;

signal processing means responsive to said accepted signal energy for determining the existence and characteristics of said targets; and

wherein said digital logic means includes means responsive to said determined target characteristics for computing a track update rate Delta T with respect to each target.

3. The system of claim 2 wherein said means for computing said track update rate Delta T includes means for computing the result of the equation:

Delta T 1.1 (R theta /m)1/2 where R defines the target range, theta defines the azimuth angle of the target, and m defines the tangential acceleration of the target.

4. The system of claim 2 including memory means for storing said track update rates computed for each of said targets;

and wherein said priority means includes means for determining the track priority PT for each of said targets where PT TC - TLU/ Delta T where TC represents the current real time, TLU represents the time of last update of the target data and Delta T represents the target track update rate.

5. The system of claim 4 wherein said priority means includes means for determining the search priority PS where PS TC -TLS/ Delta TS where TC represents the current real time, TLS represents thE time of issuance of the last search radar control command and Delta TS represents the intended time between issuance of successive search radar control commands.

6. The system of claim 5 including means for determining the value of said term Delta TS where Delta TS K.N + Delta TSN where K is a constant, N equals the number of track update rates stored in said memory means and Delta TSN is a constant representing a nominal search rate.

7. The system of claim 6 wherein said priority means further includes:

means for determining whether the largest of said track priorities PT is greater or less than 1; and

being responsive to said largest track priority being less than 1 for enabling said search command means to issue a search radar control command;

means responsive to said largest track priority exceeding 1 for comparing the relative manitudes of said search priority and said largest track priority for enabling said search command means if said search priority is larger and said track command means if said largest track priority is larger.

8. The system of claim 2 wherein said priority means includes means for determining the search priority PS where PS TC -TLS/ Delta TS where TC represents the current real time, TLS represents the time of issuance of the last research radar control command and Delta TS represents the intended time between issuance of successive search radar control commands.

9. The system of claim 2 wherein said digital logic means further includes verify command means for producing a radar control command specifying a verify beam mode and an azimuth position within said azimuth volume;

and means responsive to the determination of a target existing subsequent to signal energy characteristic of said search mode being supplied to said antenna structure for enabling said verify command means.

10. The system of claim 1 wherein said digital logic means comprises a stored program digital computer.

11. A method of controlling an airborne radar system including a plurality of fixed beam steered antenna structures mounted in an aircraft, each directed at different sectors within a 360* surveillance volume;

said method comprising the steps of;

firing successive search beams, each having a particular search mode format from said antenna structure at successively different azimuth angles within said surveillance volume;

monitoring the signal energy reflected to said antenna structures to determine the characteristics of reflecting targets;

storing information items, each describing the characteristics of a particular reflecting target in a certain class of reflecting targets;

determining the rate at which each of said stored information items should be updated;

periodically firing a track beam, having a particular track mode format, from said antenna structures corresponding to each of said stored information items; and

determining the priority between each of said track beams to be fired and the next successive search beam to be fired.

12. The method of claim 11 wherein said step of monitoring to determine the characteristics of reflecting targets includes the steps of tentatively determining the location of a target and firing a verify beam, having a particular verify mode format, from said antenna structures toward said tentatively located target.