Noise riding threshold control with immunity to signals with high pulse repetition frequencies and high duty cycles

• US 6,433,730 B1
• Filed: 06/07/2001
• Issued: 08/13/2002
• Est. Priority Date: 06/07/2001
• 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: Borla, John D.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/867,700
• Time in Patent Office: 432 Days
• Field of Search: 342/13, 342/89, 342/91, 342/92, 342/93, 342/94, 342/99, 342/159, 342/162, 342/192, 342/195, 342/196, 342/197
• US Class Current: 342/91
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
• CPC Class Codes: G01S 7/2922 by using a controlled threshold

Abstract

A system and method is disclosed for a radar receiver, such as a wideband crystal video early warning receiver, to automatically detect the noise level of the radar receiver with immunity to high pulse repetition frequencies and high duty cycle signals. The noise riding threshold circuit utilizes high frequency components of the noise and, to the attenuated extent present, high frequency components of the video signal to produce the noise riding threshold voltage. An amplifier gain control permits adjusting the noise-riding threshold to a fixed relative level. In a preferred embodiment, the noise riding threshold control of the present invention utilizes current feedback amplifiers for wide bandwidth, high gain video amplifiers.

Claims

1. A radar receiver, comprising:

a detector for receiving a radar signal and removing a carrier frequency signal to produce a video signal with noise;

one or more amplifiers for amplifying said video signal with said noise to produce an amplified signal;

a noise riding threshold control for receiving said amplified signal, said noise riding threshold control being operable for producing a dc threshold signal; and

a comparator for receiving said amplified signal and said dc threshold signal.

2. The radar receiver of claim 1, wherein said noise riding threshold control further comprises one or more current feedback video amplifiers.

3. The radar receiver of claim 1, wherein said noise riding threshold control further comprises a first video amplifier with a gain control.

4. The radar receiver of claim 3, wherein said noise riding threshold control further comprises a second video amplifier with one or more rectifiers for producing a rectified signal.

5. The radar receiver of claim 4, wherein said noise riding threshold control further comprises a high pass filter with a low frequency cutoff greater than 500 KHz disposed between said first video amplifier and said second video amplifier.

6. The radar receiver of claim 5, wherein said noise riding threshold control further comprises a low pass filter with a high frequency cutoff less than 10 Hz for integrating said rectified signal.

7. The radar receiver of claim 1, wherein said noise riding threshold control further comprises:

a first current feedback amplifier for receiving said amplified signal; and

a potentiometer being associated with said first current feedback amplifier for adjusting a gain thereof.

8. A method for detecting a radar signal, comprising:

envelope detecting said radar signal to remove a carrier signal and produce a combination signal having a video signal with a noise signal, said video signal having high frequency video signal components above 500 KHz and low frequency video signal components below 500 KHz, said noise signal having high frequency noise components above 500 KHz and low frequency noise components below 500 KHz;

filtering said combination signal to obtain said high frequency video signal components above 500 KHz and said high frequency noise components above 500 KHz;

rectifying said high frequency video signal components above 500 KHz and said high frequency noise components above 500 KHz to produce a rectified signal;

integrating said rectified signal to produce a noise riding threshold signal; and

comparing said combination signal and said noise riding threshold signal.

9. The method of claim 8, further comprising applying said combination signal to a first path and a second path, said first path being used for connecting said combination signal to a comparator, said second path being used-for connecting said combination signal to a noise riding threshold control.

10. The method of claim 9, further comprising adjustably amplifying said combination signal in said second path.

11. The method of claim 9, further comprising amplifying said combination signal in said second path with one or more amplifiers employing current feedback.

12. The method of claim 8, wherein said step of detecting further comprises applying said radar signal to a Schottkey detector.

13. The method of claim 8, further comprising adjusting said noise riding threshold signal to a predetermined level with respect to said high frequency noise components above 500 KHz.

14. A radar receiver, further comprising:

a detector for receiving a radar signal and removing a carrier frequency signal to produce a video signal with noise;

a first current feedback amplifier for amplifying said video signal with said noise;

a high pass filter connected to an output of said first current feedback amplifier to produce a filtered signal;

a second current feedback amplifier with one or more rectifiers for amplifying and rectifying said filtered signal to produce a rectified signal;

a low pass filter for integrating said rectified signal to produce a threshold signal; and

a comparator for receiving said threshold signal and said video signal with noise.

15. The radar receiver of claim 14, wherein said high pass filter has a low frequency cutoff greater than 500 KHz.

16. The radar receiver of claim 14, wherein said low pass filter has a high frequency cutoff less than 10 Hz.

17. The radar receiver of claim 14, wherein said detector comprises a Schottkey detector.

18. The radar receiver of claim 14, further comprising an adjustable resistor for controlling a gain of said first current feedback amplifier.