Signal detection in high noise environments

• US 5,909,178 A
• Filed: 11/28/1997
• Issued: 06/01/1999
• Est. Priority Date: 11/28/1997
• Status: Expired due to Term

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Allen, John A., Balch, Brent F.
• Primary Examiner(s): TONG, NINA C
• Application Number:
  US08/980,484
• Time in Patent Office: 550 Days
• Field of Search: 340/572.4, 340/572.1, 340/551, 340/552
• US Class Current: 340/572.4
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 29/24 Self-calibration, e.g. compensating for environmental drift or ageing of components

Abstract

A method for adjusting a validation threshold for detecting a marker in an interrogation zone of an electronic surveillance system, comprising the steps of: (a.) tracking individual moving averages of background noise in a plurality of operational phase windows; (b.) tracking a moving variance for each of the moving averages of the background noise in each of the plurality of windows; and, (c.) continuously adjusting a validation threshold for detecting the marker in the interrogation zone responsive to the moving averages and responsive to the moving variances.

Claims

1. A method for adjusting a validation threshold for detecting a marker in an interrogation zone of an electronic surveillance system, comprising the steps of:

(a.) tracking individual moving averages of background noise in a plurality of operational phase windows;

(b.) tracking a moving variance for each of said moving averages of said background noise in each of said plurality of windows; and

,

(c.) continuously adjusting a validation threshold for detecting said marker in said interrogation zone responsive to said moving averages and responsive to said moving variances.

2. The method of claim 1, further comprising the steps of:

continuously calculating a weighted moving average based on said moving averages in said step (a.); and

,

tracking said moving variance in said step (b.) for each of said weighted moving averages.

3. The method of claim 2, further comprising the steps of:

calculating a standard deviation of said moving variances; and

,

continuously adjusting said validation threshold for detecting said marker in said interrogation zone in said step (c.) responsive to said moving averages and responsive to said standard deviation.

4. The method of claim 2, further comprising the step of adjusting the size of said weighted moving average by a programmable factor to control a response time of said method.

5. The method of claim 2, further comprising the steps of:

comparing said validation threshold to a programmed minimum signal-to-noise ratio; and

,

preventing said validation threshold from falling below said programmed minimum signal-to-noise ratio.

6. The method of claim 1, further comprising the steps of:

continuously calculating an exponential moving average based on said moving averages in said step (a.); and

,

tracking said moving variance in said step (b.) for each of said exponential moving averages.

7. The method of claim 6, further comprising the steps of:

calculating a standard deviation of said moving variances; and

,

continuously adjusting said validation threshold for detecting said marker in said interrogation zone in said step (c.) responsive to said moving averages and responsive to said standard deviation.

8. The method of claim 6, further comprising the step of adjusting the size of said exponential moving average by a programmable factor to control a response time of said method.

9. The method of claim 6, further comprising the steps of:

comparing said validation threshold to a programmed minimum signal-to-noise ratio; and

,

preventing said validation threshold from falling below said programmed minimum signal-to-noise ratio.

10. The method of claim 1, further comprising the steps of:

calculating a standard deviation of said moving variances; and

,

continuously adjusting said validation threshold for detecting said marker in said interrogation zone in said step (c.) responsive to said moving averages and responsive to said standard deviation.

11. The method of claim 10, further comprising the steps of:

comparing said validation threshold to a programmed minimum signal-to-noise ratio; and

,

preventing said validation threshold from falling below said programmed minimum signal-to-noise ratio.

12. The method of claim 1, further comprising the steps of:

comparing said validation threshold to a programmed minimum signal-to-noise ratio; and

,

preventing said validation threshold from falling below said programmed minimum signal-to-noise ratio.

13. A method for adjusting a validation threshold for detecting a marker with a receiver in an interrogation zone of an electronic surveillance system, comprising the steps of:

(a.) tracking at least one statistical characteristic of a signal received by said receiver in a plurality of operational phase windows;

(b.) tracking a statistical variance for said at least one statistical characteristic of said signal received by said receiver in each of said plurality of windows; and

,

(c.) continuously adjusting a validation threshold for detecting said marker in said interrogation zone responsive to said statistical variance.

14. The method of claim 13, further comprising the step of also continuously adjusting said validation threshold responsive to said at least one statistical characteristic.

15. The method of claim 14, further comprising the steps of:

comparing said validation threshold to a programmed minimum signal-to-noise ratio; and

,

preventing said validation threshold from falling below said programmed minimum signal-to-noise ratio.

16. The method of claim 13, comprising the step of tracking background noise as said signal received by said receiver.

17. The method of claim 13, further comprising the steps of:

comparing said validation threshold to a programmed minimum signal-to-noise ratio; and

,

preventing said validation threshold from falling below said programmed minimum signal-to-noise ratio.