EAS system employing pseudorandom coding system and method

• US 6,750,768 B2
• Filed: 09/04/2002
• Issued: 06/15/2004
• Est. Priority Date: 04/15/2002
• Status: Active Grant

• Current Assignee: Eas Sensor Sense, W G Security Products Incorporated
• Original Assignee: Eas Sensor Sense, W G Security Products Incorporated
• Inventors: Yang, Xiaohui, Fuss, Arthur
• Primary Examiner(s): Pham, Toan N.
• Application Number:
  US10/235,167
• Publication Number:
  US 20030231113A1
• Time in Patent Office: 650 Days
• Field of Search: 340/571, 340/568.1, 340/572.1, 340/572.4, 340/572.5, 340/572.7, 235/382, 235/439, 235/449, 235/494
• US Class Current: 340/571
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2488 Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence

Abstract

According to the invention, a system and method of reducing noise interference in a way that employs pseudorandom coding. A transmitter and receiver are provided to send and receive a string of non-periodic pulses. The string of non-periodic pulses can be a sequence of pseudorandom codes. The random transmission of pulses in a non-periodic manner promotes a significant immunity to periodic interferences of constant noise operating in a surveillance area. The string of non-periodic pulses can be mutually spaced and binary, in the form of 0 or 1, and can include several bits per cycle to measure the mean and standard deviation of the string of non-periodic pulses received. A circuit is coupled to the transmitter and receiver for comparing the portion of the string of non-periodic pulses received with the string of non-periodic pulses transmitted; and whereby an alarm in triggered if the portion of the string of non-periodic pulses is above a threshold value.

Claims

1. A method of reducing noise interference, the method comprising the steps of:

a) transmitting a string of non-periodic pulses;

b) receiving a portion of the string of non-periodic pulses;

c) calculating a mean and standard deviation of the portion of the string of non-periodic pulses received;

d) comparing the portion of the string of non-periodic pulses received with the string of non-periodic pulses transmitted; and

e) triggering an alarm if the portion of the string of non-periodic pulses received is above a threshold value.

2. The method of claim 1 wherein the string of non-periodic pulses is a sequence of pseudorandom codes.

3. The method of claim 1 wherein the string of non-periodic pulses is binary.

4. The method of claim 3 wherein the string of non-periodic pulses is more than 6 bits per cycle and less than 12 bits per cycle.

5. The method of claim 1 wherein the string of non-periodic pulses is mutually spaced.

6. The method of claim 1 further including the step of recording the portion of the string of non-periodic pulses.

7. The method of claim 1 wherein the threshold value is a predetermined number.

8. The method of claim 7 wherein the predetermined number is binary.

9. A security system, comprising:

a) means for transmitting a string of non-periodic pulses;

b) means for receiving a portion of the string of non-periodic pulses;

c) means for calculating a mean and standard deviation of the portion of the string of non-periodic pulses received;

d) means for comparing the portion of the string of non-periodic pulses received with the string of non-periodic pulses transmitted; and

e) means for triggering an alarm if the portion of the string of non-periodic pulses is above a threshold value.

10. The system in accordance with claim 9, wherein the string of non-periodic pulses is a sequence of pseudorandom codes.

11. The system in accordance with claim 9, wherein the string of non-periodic pulses is binary.

12. The system in accordance with claim 11, wherein the string of non-periodic pulses is more than 6 bits per cycle and less than 12 bits per cycle.

13. The system in accordance with claim 9, wherein the string of non-periodic pulses is mutually spaced.

14. The system in accordance with claim 9, further including means for recording the portion of the string of non-periodic pulses.

15. The system in accordance with claim 9, wherein the threshold value is a predetermined number.

16. The system in accordance with claim 15, wherein the predetermined number is binary.

17. A security system, comprising:

a) a transmitter for transmitting a string of non-periodic pulses;

b) a receiver for receiving a portion of the string of non-periodic pulses; and

c) a circuit coupled to the transmitter and the receiver for calculating a mean and standard deviation of the portion of the string of non-periodic pulses received and comparing the portion of the string of non-periodic pulses with the string of non-periodic pulses transmitted; and

whereby an alarm is triggered if the portion of the string of non-periodic pulses is above a threshold value.

18. The system in accordance with claim 17, wherein the string of non-periodic pulses is a sequence of pseudorandom codes.

19. The system in accordance with claim 17, wherein the string of non-periodic pulses is binary.

20. The system in accordance with claim 19, wherein the string of non-periodic pulses is more than 6 bits per cycle and less than 12 bits per cycle.

21. The system in accordance with claim 17, wherein the string of non-periodic pulses is mutually spaced.

22. The system in accordance with claim 17, wherein the threshold value is a predetermined number.

23. The system in accordance with claim 22, wherein the predetermined number is binary.