Short-range point defense radar

1. A method for simultaneous detection of multiple short-range targets using radar, comprising:

(a) illuminating a wide field of regard with frequency-modulated continuous wave radar signals comprising a sequence of linear frequency-modulated sweeps using a transmit antenna;

(b) for each linear frequency-modulated sweep of said sequence, receiving radar signals reflected from the field of regard within a short range using a receive antenna array having a multiplicity of antenna elements;

(c) converting the reflected radar signals into a respective multiplicity of pencil beams for each linear frequency-modulated sweep of said sequence using two-dimensional beamforming; and

(d) for each linear frequency-modulated sweep of said sequence, detecting any pencil beams of said multiplicity of pencil beams having a characteristic indicative that radar signals were reflected from a target in the field of regard,

wherein said two-dimensional beamforming and said target detection are performed by a computer system.

2. The method as recited in claim 1 , wherein step (c) comprises:

converting the received radar signals into respective digital in-phase and quadrature samples for each antenna element;

forming a respective multiplicity of simultaneous azimuth beams from said digital in-phase and quadrature samples for each linear frequency-modulated sweep of said sequence, said azimuth beams of each multiplicity being aimed at respective azimuth angles; and

forming the respective multiplicity of pencil beams from said azimuth beams for each linear frequency-modulated sweep of said sequence using elevation beamforming.

3. The method as recited in claim 1 , wherein step (d) comprises:

forming a multiplicity of range bins for each pencil beam;

Doppler processing said range bins across multiple linear frequency-modulated sweeps; and

computing a range of the target based on results of said Doppler processing.

4. The method as recited in claim 1 , further comprising starting a track on the target when an M of N target detection threshold is reached, where M and N are positive integers and M<N.

5. The method as recited in claim 4 , further comprising continuously updating the track on the target.

6. The method as recited in claim 5 , wherein the track is continuously updated every coherent integration time.

7. The method as recited in claim 1 , further comprising computing azimuth and elevation angles of the target using angle discrimination.

8. The method as recited in claim 1 , wherein the transmit antenna and the receive antenna array are at different locations.

9. A radar system capable of simultaneous detection of multiple short-range targets, comprising:

an exciter capable of generating frequency-modulated continuous wave radio frequency signals comprising a sequence of linear frequency-modulated sweeps;

a receiver comprising a multiplicity of mixers for mixing radio frequency signals with replicas of said frequency-modulated continuous wave radio frequency signals and outputting analog signals;

one or more antennas for converting frequency-modulated continuous wave radio frequency signals generated by said exciter into electromagnetic waves and converting returned electromagnetic waves into radio frequency signals which are sent to said receiver;

means for converting analog signals from said receiver into digital samples;

a digital azimuth beamformer that forms a multiplicity of narrow azimuth beams from digital samples produced for each linear frequency-modulated sweep;

a digital elevation beamformer that forms a multiplicity of pencil beams from the multiplicity of narrow azimuth beams produced for each linear frequency-modulated sweep; and

a digital signal processor programmed to detect any pencil beams of said multiplicity of pencil beams having a characteristic indicative that radar signals were reflected from a target in the field of regard for each linear frequency-modulated sweep.

10. The radar system as recited in claim 9 , wherein said digital signal processor is programmed to perform the following operations:

forming a multiplicity of range bins for each pencil beam;

Doppler processing said range bins across multiple linear frequency-modulated sweeps; and

computing a range of the target based on results of said Doppler processing.

11. The radar system as recited in claim 9 , further comprising a track processor programmed to start a track on the target when an M of N target detection threshold is reached, where M and N are positive integers and M<N.

12. The radar system as recited in claim 11 , wherein said track processor is further programmed to continuously update the track on the target.

13. A method for simultaneous detection of multiple short-range targets using radar, comprising:

(a) illuminating a wide field of regard with frequency-modulated continuous wave radar signals comprising a sequence of linear frequency-modulated sweeps using a transmit antenna;

(b) for each linear frequency-modulated sweep of said sequence, receiving radar signals reflected from the field of regard within a short range using a receive antenna array having a multiplicity of antenna elements;

(c) converting the reflected radar signals into a respective multiplicity of fan beams for each linear frequency-modulated sweep of said sequence using two-dimensional beamforming;

(d) for each linear frequency-modulated sweep of said sequence, detecting any fan beams of said multiplicity of fan beams having a characteristic indicative that radar signals were reflected from a target in the field of regard; and

(e) forming a multiplicity of pencil beams for any fan beam for which a target was detected,

wherein said two-dimensional beamforming and steps (d) and (e) are performed by a computer system.

14. The method as recited in claim 13 , wherein step (d) comprises:

forming a multiplicity of range bins for each pencil beam;

Doppler processing said range bins across multiple linear frequency-modulated sweeps; and

computing a range of the target based on results of said Doppler processing.

15. The method as recited in claim 13 , further comprising starting a track on the target when an M of N target detection threshold is reached, where M and N are positive integers and M<N.

16. The method as recited in claim 15 , further comprising continuously updating the track on the target.

17. The method as recited in claim 16 , wherein the track is continuously updated every coherent integration time.

18. The method as recited in claim 13 , further comprising computing azimuth and elevation angles of the target using angle discrimination for any pencil beams of said multiplicity of pencil beams having a characteristic indicative that radar signals were reflected from a target in the field of regard.

19. A radar system capable of simultaneous detection of multiple short-range targets, comprising:

an exciter capable of generating frequency-modulated continuous wave radio frequency signals comprising a sequence of linear frequency-modulated sweeps;

a receiver comprising a multiplicity of mixers for mixing radio frequency signals with replicas of said frequency-modulated continuous wave radio frequency signals and outputting analog signals;

one or more antennas for converting frequency-modulated continuous wave radio frequency signals generated by said exciter into electromagnetic waves and converting returned electromagnetic waves into radio frequency signals which are sent to said receiver;

means for converting analog signals from said receiver into digital samples;

a digital azimuth beamformer that forms a multiplicity of narrow azimuth beams from digital samples produced for each linear frequency-modulated sweep;

a first digital elevation beamformer that forms a multiplicity of fan beams from the multiplicity of narrow azimuth beams produced for each linear frequency-modulated sweep;

a digital signal processor programmed to detect any fan beams of said multiplicity of pencil beams having a characteristic indicative that radar signals were reflected from a target in the field of regard for each linear frequency-modulated sweep; and

a second digital elevation beamformer that forms a multiplicity of pencil beams for any fan beam for which a target was detected.

20. The radar system as recited in claim 19 , further comprising digital angle discrimination means for computing azimuth and elevation angles of the target for any pencil beams of said multiplicity of pencil beams having a characteristic indicative that radar signals were reflected from a target in the field of regard.