SYSTEM AND METHOD FOR REDUCING INTERFERENCE IN MICROWAVE MOTION SENSORS

• US 20090160697A1
• Filed: 12/20/2007
• Published: 06/25/2009
• Est. Priority Date: 12/20/2007
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Wu, Xiaodong
• Granted Patent: US 7,872,604 B2
• Time in Patent Office: Days
• US Class Current: 342/28
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves

Abstract

A microwave sensor comprises an oscillator configured to generate a microwave signal at a pre-determined frequency, and an antenna configured to transmit the microwave signal and/or to receive reflected signals. The antenna is linear polarized at 45 degrees and the transmitted microwave signal has an electric field at 45 degrees to the plane of the horizontal. The microwave sensor further includes a signal processor coupled to the antenna and configured to process the reflected signals to determine a presence of a moving object.

Claims

1. A microwave sensor comprising:

an oscillator configured to generate a microwave signal at a pre-determined frequency;

an antenna configured to transmit the microwave signal and to receive reflected signals, wherein the antenna is linear polarized at 45 degrees, and wherein the transmitted microwave signal has an electric field at 45 degrees to the plane of the horizontal; and

a signal processor coupled to the antenna and configured to process the reflected signals to determine a presence of a moving object.

2. The microwave sensor of claim 1, further comprising a mixer coupled to the antenna and the oscillator and configured to mix the reflected signal with a portion of the transmitted microwave signal to generate a corresponding intermediate frequency signal.

3. The microwave sensor of claim 1, wherein the antenna comprises one of a single patch antenna, patch array, a single slot antenna, a slot array, a horn antenna, and a combination thereof.

4. The microwave sensor of claim 1, wherein the antenna comprises of sensors in one of a 1×

2 array, 2×

2 array or N×

M array.

5. The microwave sensor of claim 1, wherein the processor is further configured to generate an alarm based on the presence of a moving object.

6. The microwave sensor of claim 1, wherein the antenna further comprises a separate transmitting antenna and a separate receiving antenna.

7. The microwave sensor of claim 6, wherein the transmitting antenna and the receiving antenna are both linear polarized at 45 degrees.

8. The microwave sensor of claim 6, further comprising a pulse generator configured to synchronize the transmitter and the sample/hold circuit in a signal conditioning circuitry by providing a gating signal to the signal conditioning circuitry.

9. The microwave sensor of claim 2, further comprising a signal conditioning circuitry coupled to the mixer and the signal processor and configured to condition the reflected signals, by sampling and holding, filtering and amplifying the signals.

10. A method for detecting a presence of a moving object, the method comprising:

generating a plurality of microwave signals at a corresponding pre-determined frequency, wherein the plurality of microwave signals are linear polarized having an electric field at 45 degrees;

transmitting the plurality of microwave signals;

receiving a plurality of reflected signals; and

processing the reflected signals to determine a presence of a moving object.

11. The method of claim 10, further comprising mixing the reflected signals with a portion of the transmitted microwave signal to generate a corresponding intermediate frequency mixed signal.

12. The method of claim 11, further comprising conditioning the mixed signal prior to the processing step.

13. The method of claim 10, further comprising generating an alarm based on the presence of the moving object.

14. A security system comprising:

at least two microwave sensors located in the detection area facing each other, each microwave sensor comprising;

an oscillator configured to generate a microwave signal at a pre-determined frequency;

at least an antenna configured to transmit the microwave signal and/or to receive reflected signals, wherein the antenna is linear polarized at 45 degrees; and

a signal processor coupled to the antenna and configured to process the reflected signals to determine a presence of a moving object.

15. The security system of claim 14, wherein the microwave sensor further comprises a mixer coupled to the antenna and the oscillator and configured to mix the reflected signals with a portion of the transmitted microwave signal to generate a corresponding intermediate frequency mixed signal, and a signal conditioning circuitry configured to condition the mixed signal prior to being processed.

16. The security system of claim 14, wherein the antenna comprises one of a patch array, a slot array, a single patch, a single slot, a horn antenna, and a combination thereof.

17. The security system of claim 14, wherein for each of the at least two microwave sensors, the microwave signal has an electric field at 45 degrees to the horizontal and parallel to the plane of the corresponding microwave sensor.

18. The security system of claim 14, further comprising an alarm coupled to each microwave sensor, wherein the microwave sensor is configured to trigger the alarm based on the presence of a moving object.

19. The security system of claim 14, wherein electric fields of the at least two microwave sensors are perpendicular to each other.

20. The security system of claim 14, wherein the at least two microwave sensors achieve a cross polarized operation.

21. A microwave sensor comprising:

an oscillator configured to generate a microwave signal at a pre-determined frequency;

an antenna configured to transmit the microwave signal and to receive reflected signals, wherein the antenna exhibits a selected amount of linear polarization, and wherein the transmitted microwave signal has an electric field oriented at a selected angle relative to the plane of the horizontal; and

a signal processor coupled to the antenna and configured to process the reflected signals to determine a presence of a moving object and generate an alarm based on the presence of a moving object.

22. The microwave sensor of claim 21, further comprising a mixer coupled to the antenna and the oscillator and configured to mix the reflected signal with a portion of the transmitted microwave signal to generate a corresponding intermediate frequency signal, and including signal conditioning circuitry coupled to the mixer and the signal processor and configured to condition the reflected signals, by sampling and holding, filtering and amplifying the signals.

23. The microwave sensor of claim 21, wherein the antenna comprises one of a single patch antenna, patch array, a single slot antenna, a slot array, a horn antenna, and a combination thereof.

24. The microwave sensor of claim 21, wherein the antenna comprises one of a 1×

2 array, 2×

2 array or N×

M array.

25. The microwave sensor of claim 21, wherein the antenna further comprises a separate transmitting antenna and a separate receiving antenna and where the transmitting antenna and the receiving antenna are both linearly polarized at 45 degrees.

26. The microwave sensor of claim 25, further comprising a pulse generator configured to synchronize the transmitter and the sample/hold circuit in signal conditioning circuitry by providing a gating signal to the signal conditioning circuitry.

27. A method for detecting a presence of a moving object, the method comprising:

generating a plurality of microwave signals at a corresponding pre-determined frequency, wherein members of the plurality of microwave signals are linearly polarized having an electric field oriented at a selected angle;

transmitting the plurality of microwave signals;

receiving a plurality of reflected signals;

processing the reflected signals to determine a presence of a moving object; and

generating an indicium indicative of the presence of the moving object.

28. The method of claim 27, further comprising mixing the reflected signals with a portion of the transmitted microwave signal to generate a corresponding intermediate frequency mixed signal.

29. A security system comprising:

at least two microwave sensors located in the detection area facing each other, each microwave sensor comprising;

an oscillator configured to generate a microwave signal at a pre-determined frequency;

at least an antenna configured to transmit the microwave signal and/or to receive reflected signals, wherein the antenna is linearly polarized; and

a signal processor coupled to the antenna and configured to process the reflected signals to determine a presence of a moving object.

30. The security system of claim 29, wherein the microwave sensor further comprises a mixer coupled to the antenna and the oscillator and configured to mix the reflected signals with a portion of the transmitted microwave signal to generate a corresponding intermediate frequency mixed signal, and a signal conditioning circuitry configured to condition the mixed signal prior to being processed.

31. The security system of claim 30, wherein for each of the at least two microwave sensors, the microwave signal has an electric field at 45 degrees to the horizontal and parallel to the plane of the corresponding microwave sensor.

32. The security system of claim 29, wherein electric fields of the at least two microwave sensors are perpendicular to each other.

33. The security system of claim 29, wherein the at least two microwave sensors achieve a cross polarized operation.