Jammer reference target measurement system

• US 5,359,329 A
• Filed: 03/18/1981
• Issued: 10/25/1994
• Est. Priority Date: 03/18/1981
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Lewis, Bernard L., Kretschmer, Frank F. Jr.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US06/247,578
• Time in Patent Office: 4,969 Days
• Field of Search: 343/16 M, 343/55 W, 343/100 LE, 343/ 18 E, 342/149, 342/17, 342/379-384
• US Class Current: 342/17
• CPC Class Codes: G01S 13/44 Monopulse radar, i.e. simultaneous lobing
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: G01S 7/36 Means for anti-jamming , e.g. ECCM, i.e. electronic counter-counter measures

Abstract

A system for cancelling jammer signals entering the mainlobe of a monopulseadar and providing target locations with respect to the jammer position comprising for a sequential lobing embodiment: measuring the angular position of the jammer in the radar'"'"'s mainlobe via the use of monopulse sum and difference signals, pointing the radar antenna so that the jammer is positioned within the 3 dB points of the mainlobe of the monopulse antenna, converting the sum and difference echo signals received with the antenna in this position from the next radar transmission into a second set sum and difference signals, applying this second set of sum and second set of difference signals to the inputs of an adaptive canceller to cancel the jamming signal therein and storing these signals in time sequential order, changing the orientation of the radar antenna by a small arbitrary elevation angle, converting the sum and difference echo signals received with the antenna in this new position from a third radar transmission into a third set of sum and difference signals, applying this third set of sum signals and third set of difference signals in reverse order relative to the second set of signals to the inputs of an adaptive canceller to cancel the jamming signal therein, reading out the adaptively cancelled stored echo signals from the second radar transmission into one input of a divider in time coincidence with the application of the adaptively cancelled echo signals from the same targets from the third radar transmission to the other input of the divider to obtain ratio signals proportional to the elevation angle separating the individual targets from the jammer.

Claims

1. A system for cancelling signals from a jammer entering the mainlobe of the antenna of a monopulse radar and for providing target locations with respect to the location of the jammer comprising:

means for notching the antenna response at the jammer location with the antenna pointing so that the jammer is positioned within the 3 dB points of the mainlobe of the antenna;

means for shifting the effective orientation of said antenna by a small amount and notching the antenna response at the jammer location at the new effective orientation, said new orientation being such that the jammer is still located approximately within the 3 dB points of the new mainlobe orientation; and

means for determining the ratio between echo signals from the same targets in these two notched antenna responses, said ratio being proportional to the angle separating the target in the response from the jammer.

2. A method for cancelling signals from a jammer entering the mainlobe of the antenna of a monopulse radar and for providing target locations with respect to the location of the jammer comprising the steps of:

notching the antenna response at the jammer location with the antenna pointing so that the jammer is positioned within the 3 dB points of the mainlobe of the antenna;

shifting the effective orientation of the antenna and notching the antenna response of the jammer location at this new effective orientation, said new orientation being such that the jammer is still located approximately within the 3 dB points of the new mainlobe orientation; and

determining the ratio between any echo signals from the same targets in these two notched antenna responses;

said ratio being proportional to the angle separating the target in the response from the jammer.

3. A method for cancelling signals from a jammer entering the mainlobe of the antenna of a monopulse radar and for providing target locations with respect to the location of the jammer comprising the steps of:

receiving a first set of echo and jamming signals and determining the position of the jammer therefrom;

effectively orienting the boresight axis of said monopulse radar antenna to point so that the jammer is positioned within the 3 dB points of the antenna mainlobe;

receiving a second set of echo and jamming signals reflected from the next radar transmission after said orienting step;

adaptively cancelling the jammer signal from the second set of received echo and jamming signals;

storing this second set of adaptively cancelled echo signals in time sequential order;

effectively changing the orientation of the boresight axis of said monopulse radar antenna by a small arbitrary angle θ

such that the jammer is still located approximately within the 3 dB points of the new mainlobe orientation of the antenna;

receiving a third set of echo and jamming signals reflected from the next radar transmission after said orientation changing step;

adaptively cancelling the jamming signals from this third set of received echo and jamming signals;

reading-out said second set of stored adaptively cancelled echo signals in time coincidence with the occurrence of the adaptively cancelled echo signals in said third set reflected from the same targets; and

dividing the adaptively cancelled echo signals in one of the second or third sets, e.g., the second set, by the time coincident adaptively cancelled echo signals in the other of the second or third sets, e.g., the third set, to obtain a set of ratio signals which are proportional to the angles separating the individual targets from the jammer.

4. A method as defined in claim 3, further comprising the step of converting the ratio signal generated in said dividing step to an angle value.

5. A method as defined in claim 4, wherein said monopulse radar has two effective antenna apertures which provide signal pairs and wherein said first set receiving step includes the steps of

generating a first set of sum and difference signals from the signal pairs from said two effective apertures;

and

utilizing said first set of sum and difference signals to determine the location of said jammer;

and wherein said second set receiving step includes the steps of;

generating a second set of sum and difference signals from the second set of signal pairs from said two effective apertures; and

generating a third set of sum and difference signals from said second set of sum and difference signals; and

wherein said third set receiving step includes the steps of;

generating a fourth set of sum and difference signals from the third set of signal pairs from said two effective apertures; and

generating a fifth set of sum and difference signals from said fourth set of sum and difference signals.

6. A method as defined in claim 5, wherein the first adaptive cancelling step comprises the step of applying the third set of sum signals as the main signal and the third set of difference signals as the auxiliary signal in an adaptive cancellation process;

and

wherein the second adaptive cancelling step comprises the step of applying the fifth set of sum signals as the auxiliary signal and the fifth set of difference signals as the main signal in an adaptive cancellation process.

7. A method for cancelling jammer signals entering the mainlobe of a monopulse radar having two effective antenna apertures, and for providing target locations with respect to the location of the jammer comprising the steps of:

receiving a first set of echo signal pairs from a first radar transmission along with jamming signals from said two effective antenna apertures;

generating a first set of sum and difference signals from said first set of signal pairs;

determining the angular position of the jammer with respect to the boresight axis of the two effective antenna apertures utilizing said first set of sum and difference signals;

orienting the boresight axis of the two effective antenna apertures to point so that the jammer is positioned within the 3 dB points of the mainlobe of said two effective antenna apertures;

receiving a second set of echo signal pairs from a second radar transmission along with jamming signals from said two effective antenna apertures after said orienting step;

generating a second set of sum and difference signals from said second set of received echo signal pairs;

generating a third set of sum and difference signals from said second set of sum and difference signals;

adaptively cancelling the jamming signal by utilizing either the third set of sum or the third set of difference signals as the main signal, e.g., the third set of sum signals, and the other set, e.g., the third set of difference signals, as the auxiliary signal in an adaptive cancelling process;

storing this adaptively cancelled set of echo signals in time sequence;

changing the orientation of the boresight axis of the two effective antenna apertures by an arbitrary angle such that the jammer is still located approximately within the 3 dB points of the new mainlobe orientation of the antenna;

receiving a third set of echo signal pairs from a third radar transmission along with jamming signals from said two effective antenna apertures;

generating a fourth set of sum and difference signals from said third set of each signal pairs;

generating fifth set of sum and difference signals from said fourth set of sum and difference signals;

adaptively cancelling the jamming signal by utilizing the fifth set of sum and the fifth difference signals in an order reversed from that used in the first adaptive cancelling step process, e.g., with the fifth set of sum signals utilized as the auxiliary signal and the fifth set of difference signals utilized as the main signal in an adaptive cancelling process;

reading-out the adaptively cancelled stored echo signals from said second radar transmission in time coincidence with the occurrence of the adaptively cancelled echo signals reflected from the same targets from said third radar transmission;

dividing the sequentially read-out adaptively cancelled echo signals from said second radar transmission by the adaptively cancelled echo signals from said third radar transmission to obtain a ratio signal which is proportional to the elevation angle separating the target from the jammer; and

applying this ratio signal to a look-up table to determine the target location with respect to the jammer.

8. A system for cancelling jammer signals in the mainlobe of a monopulse radar and providing target locations with respect to the location of the jammer comprising:

a monopulse radar including an antenna with two effective apertures and a boresight axis for receiving echo signals from a radar transmission at each effective aperture along with jamming signals and generating signals A'"'"' and B'"'"' therefrom;

means for converting said received echo signals A'"'"' and B'"'"' into sum and difference signals;

means for determining the angular position of the jammer with respect to the boresight axis of said monopulse radar antenna by utilizing said sum and difference signals and then effectively orienting said boresight axis to point so that said jammer is positioned within the 3 dB points of the mainlobe of said two effective antenna apertures;

adaptive canceller means with main and auxiliary inputs;

a memory

means for amplifying the received echo signals A'"'"' and B'"'"' from said two effective antenna apertures prior to conversion to sum and difference signals and applying these amplified signals to the main and auxiliary inputs of said adaptive canceller means, e.g., the A'"'"' echo signal to the main input and the B'"'"' echo signal to the auxiliary input, such that the jamming signal is cancelled from the output of said adaptive canceller means;

wherein said adaptive canceller means cancels the jamming signal from a first set of echo signals received from the next radar transmission after said monopulse antenna axis has been effectively pointed so that the jammer is within the 3 dB points of the antenna mainlobe and applies this adaptively cancelled first set of echo signals in time sequence to said memory;

means for changing the effective orientation of the boresight axis of said monopulse radar antenna by an arbitrary angle, such that the jammer is still located approximately within the 3 dB points of the new mainlobe orientation of the antenna;

first switching means for reversing the application of the amplified echo signals A'"'"' and B'"'"' to said adaptive canceller means for the next radar transmission after the effective orientation of said monopulse antenna axis has been changed by said arbitrary angle, e.g., B'"'"' to said main input and A'"'"' to said auxiliary input;

wherein said adaptive canceller means then cancels the jamming signal from a second set of echo signals received from the next radar transmission after the effective orientation of said monopulse antenna axis has been changed by said arbitrary angle;

divider means with one input port connected to the output of said memory;

second switching means for switching the adaptive canceller means echo signal output from said memory to a second input port of said divider means such that said second set of echo signals are applied thereto;

wherein said first set of adaptively cancelled stored echo signals in said memory are read-out to said divider means in time coincidence with the occurrence of adaptively cancelled echos in said second set reflected from the same targets such that a ratio signal is obtained for each target which is proportional to the angle separating the target from the jammer position.

9. A system for cancelling jammer signals in the mainlobe of a monopulse radar and providing target locations with respect to the location of the jammer comprising:

a monopulse radar including an antenna with two effective apertures and a boresight axis for receiving echo signals from a radar transmission at each effective aperture along with jamming signals and generating signals A'"'"' and B'"'"' therefrom;

first means for converting said received echo signals A'"'"' and B'"'"' into a first set of sum and difference signals A'"'"'+B'"'"' and A'"'"'-B'"'"';

means for determining the angular position of the jammer-with respect to the boresight axis of said monopulse radar antenna by utilizing said first set of sum and difference signals and then effectively orienting said boresight axis to point so that the jammer is positioned within the 3 dB points of the mainlobe of said two effective antenna apertures;

adaptive canceller means with main and auxiliary inputs;

second means for converting said first set of sum and difference signals into a second set of sum and difference signals G₁ A'"'"' and G₂ B'"'"', where G₁ and G₂ are constants, and applying the signals G₁ A'"'"' and G₂ B'"'"', in either order, to the main and auxiliary inputs of said adaptive canceller means, e.g., the G₁ A'"'"' signal to the main input and the G₂ B'"'"' signal to the auxiliary input, such that the jamming signal is cancelled at the output of said adaptive canceller means;

wherein said adaptive canceller means cancels the jamming signal from a first set of echo signals received from the next radar transmission after said monopulse antenna boresight axis has been pointed so that the jammer is positioned within the 3 dB points of the antenna mainlobe and applies this adaptively cancelled first set of echo signals in time sequence to said memory;

means for changing the effective orientation of the boresight axis of said monopulse radar antenna by an arbitrary angle such that the jammer is still located approximately within the 3 dB points of the new mainlobe orientation of the antenna;

first switching means for reversing the application of the echo signals G₁ A'"'"' and G₂ B'"'"' to said adaptive canceller means for the next radar transmission after the effective orientation of said monopulse antenna axis has been changed by said arbitrary angle, e.g., G₂ B'"'"' to said main input and G₁ A'"'"' to said auxiliary input;

wherein said adaptive canceller means then cancels the jamming signal from a second set of echo signals received from the next radar transmission after the effective orientation of said monopulse antenna axis has been changed by said arbitrary angle;

divider means with one input port connected to the output of said memory;

second switching means for switching the adaptive canceller means echo signal output from said memory to a second input port of said divider means such that said second set of echo signals are applied thereto;

wherein said first set of adaptively cancelled stored echo signals in said memory are read-out to said divider means in time coincidence with the occurrence of adaptively canceled echos in said second set reflected from the same targets such that a ratio signal is obtained for each target which is proportional to the angle separating the target from the jammer position.

10. A system as defined in claim 9, further including means for converting said ratio signal to an angle value.

11. A system as defined in claim 10, wherein said first and second sum and difference converting means are hybrids.

12. A system for cancelling jammer signals in the mainlobe of a monopulse radar and providing target locations with respect to the location of the jammer comprising:

a monopulse radar including an antenna for receiving echo signals from a radar transmission along with jamming signals and generating a first set of sum and difference signals therefrom;

means for determining the angular position of the jammer generating said jamming signals with respect to the boresight axis of said monopulse radar antenna by utilizing said sum and difference signals and then effectively orienting said antenna boresight axis to point so that the jammer is positioned within the 3 dB points of the antenna mainlobe;

means for generating a second set of sum and difference signals from said first set of sum and difference signals;

first adaptive cancelling means with main and auxiliary inputs;

second adaptive cancelling means with main and auxiliary inputs;

means for shifting the phase of said second sum signal;

means for shifting the phase of said second difference signal;

first means for adding said second sum signal to said second difference signal and applying this sum to the main input of said first adaptive canceller means and to said auxiliary input of said second adaptive canceller means;

second means for adding said phase shifted second sum signal to said second difference signal to obtain a squinted signal and applying this sum to the auxiliary input of said first adaptive canceller means;

third means for adding said second sum signal to said phase shifted second difference signal to obtain a squinted signal and applying this sum to the main input of said second adaptive cancelling means; and

means for dividing the output signal from one of said adaptive canceller means by the output from the other of said adaptive canceller means in order to obtain a ratio signal which is proportional to the angle separating the target echo from the jammer position.

13. A system as defined in claim 12, further including means connected to the output said dividing means for converting said ratio signal therefrom to an angle value.

14. A system as defined in claim 13, wherein said means for generating a sum and difference signal and said first, second, and third adding means are hybrids.

15. A system as defined in claim 14, wherein said second sum phase shifting means and said second difference phase shifting means shift the phase of their respective input signals only slightly in order to insure that the jammer will be positioned approximately within the 3 dB points of the resulting squinted mainlobes of said monopulse antenna.

16. A system for cancelling jammer signals in the mainlobe of a monopulse radar and providing target locations with respect to the location of the jammer comprising:

a monopulse radar including an antenna with two effective apertures for receiving echo signals from a radar transmission along with jamming signals;

means for determining the location of said jammer;

means for effectively pointing the boresight axis of said monopulse antenna so that the jammer is positioned within the 3 dB points of the mainlobe of said two effective antenna apertures;

first means for squinting the echo signals received from the two effective apertures of said monopulse antenna for a first angle of arrival;

first means for adding the echo signals from each of said two effective antenna apertures;

second means for squinting said echo signals from said two effective apertures of said monopulse antenna for a second angle of arrival;

first adaptive cancelling means for cancelling the jamming signal from the received echo signals by utilizing the output signals from said first adding means and said first squinting means in an adaptive cancelling process;

second adaptive cancelling means for cancelling the jamming signal from the received echo signals by utilizing the outputs from said adding means and said second squinting means in an adaptive cancelling process; and

means for taking the ratio of the output signals from one of said adaptive cancelling means with respect to the output signals from the other adaptive cancelling means, said ratio signals being proportional to the angles separating the individual targets from the jammer.

17. A system as defined in claim 16, wherein said first and second squinting means squint the monopulse antenna mainlobe only slightly so that the jammer is still located approximately within the 3 dB points of the resulting squinted antenna mainlobes.

18. A system as defined in claim 17, further comprising means connected to said ratio taking means for converting said ratio signals therefrom to an angle value.

19. A system as defined in claim 18, wherein said monopulse radar includes:

first means for generating first sum and difference signals from the signals received from the two effective antenna apertures;

means for amplifying said sum and difference signals and applying said sum and difference signals to said location determining means; and

second means for generating second sum and difference signals from said first sum and difference signals.

20. A system as defined in claim 19, wherein said first squinting means comprises:

first means for phase shifting said second sum signal; and

second adding means for adding said phase shifted second sum signal to said second difference signal;

wherein said second squinting means comprises;

second means for phase shifting said second difference signal; and

third adding means for adding said phase shifted second difference signal to said second sum signal; and

wherein said first adding means adds said second sum and difference signals together.

21. A system as defined in claim 20, wherein said first and second sum and difference generating means and said first, second, and third adding means are hybrids.

22. A system as defined in claim 21, wherein said adaptive canceller means have main and auxiliary input ports and wherein the output signal from said first adding means is applied to the main input port and the output signal from said second adding means is applied to the auxiliary input port of said first adaptive cancelling means, and wherein the output signal from said first adding means is applied to the auxiliary input port and the output signal from said third adding means is applied to said main input port of said second adaptive cancelling means.

23. A method for cancelling jammer signals in the mainlobe of a monopulse radar which includes an antenna with two effective apertures and for providing target locations with respect to the location of the jammer comprising the steps of:

receiving a first set of echo signals from a radar transmission along with jamming signals;

determining the location of the jammer from said first set of echo and jamming signals;

effectively orienting the antenna of said monopulse radar to point so that the jammer is positioned within the 3 dB points of the mainlobe of said two effective antenna apertures;

squinting the echo signals received from the two effective apertures of said monopulse antenna for a first angle of arrival;

and simultaneously adding the echo signals received from the two effective apertures of said monopulse antenna;

and simultaneously squinting the said echo signals received from the two effective apertures of said monopulse antenna for a second angle of arrival;

adaptively cancelling the jamming signal from the received echo signals by utilizing the output signals from said first squinting step and from said adding step in an adaptive cancelling process;

simultaneously adaptively cancelling the jamming signal from the received echo signals by utilizing the output signals from said adding step and said second squinting step in an adaptive cancelling process; and

dividing the output signals from one adaptive cancelling step by the output signals from the other adaptive cancelling step to obtain ratio signals which are proportional to the angles separating the individual targets from the jammer.

24. A method as defined in claim 23, wherein said squinting steps squint the monopulse mainlobe only slightly so that the jammer is still located approximately within the 3 dB points of the resulting squinted antenna mainlobes.

25. A method as defined in claim 24, further comprising the step of converting said ratio signals to angle value.

26. A method as defined in claim 25, wherein said receiving step includes the steps of:

generating a first set of sum and difference signals from the signals received from said two effective antenna apertures;

amplifying said first sum and difference signals for utilization in said location determining step; and

also

generating a second set of sum and difference signals from the amplified first set of sum and difference signals.

27. A method as defined in claim 26, wherein said first angle squinting step includes the steps of:

shifting the phase of the second set of sum signals to obtain said first angle of arrival; and

adding said phase shifted second set of sum signals to said second set of difference signals to yield a fourth set of signals; and

wherein said first adding step comprises the step of adding said second set of sum signals to said second set of difference signals to yield a fifth set of signals; and

wherein said second angle squinting step comprises the steps of;

shifting the phase of the second set of difference signals to obtain said second angle of arrival; and

adding said phase shifted second set of difference signals to said second set of sum signals to yield a sixth set of signals.

28. A method as defined in claim 27, wherein said first adaptive cancelling step comprises the step of utilizing said fifth set of signals from said first adding step as a main input signal and utilizing said fourth set of signals from said first angle squinting step as the auxiliary input signal in an adaptive cancelling process;

and

wherein said second adaptive cancelling step comprises the step of utilizing said fifth set of signals from said first adding step as an auxiliary input signal and said sixth set of signals from said second angle squinting step as the main input signal in an adaptive cancelling process.