Auto-phasing synchronization for pulsed electronic article surveillance systems

• US 6,812,843 B2
• Filed: 03/11/2002
• Issued: 11/02/2004
• Est. Priority Date: 03/11/2002
• Status: Expired due to Term

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Bergman, Adam S., Soto, Manuel A.
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US10/095,546
• Publication Number:
  US 20030169168A1
• Time in Patent Office: 967 Days
• Field of Search: 340/572.4, 340/572.1, 340/310.01, 340/310.03, 340/310.04, 340/3.2, 340/825.57, 340/825.64, 375/259, 375/354, 375/362, 375/371
• US Class Current: 340/572.4
• 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 29/26 by updating and storing reference thresholds

Abstract

Automatic phase adjustment of a pulsed electronic article surveillance transmitter is provided. Amplitude sampling of a received signal is used to detect the leading edge of a interfering transmit pulse and a corresponding delay is calculated for synchronizing the instant transmitter to the interfering transmitter. Detection of EAS tags placed too close to the EAS transmitter interrogation zone is also provided. An alarm can be implemented to indicate detected EAS tags that are placed too close to the interrogation zone.

Claims

1. A method for automatic phase adjustment for synchronizing a pulsed electronic article surveillance system transmitter to an interfering transmitter, comprising:

a) detecting a signal in a preselected frequency range;

b) comparing said detected signal to a threshold value;

c) incrementing a counter value if said detected signal is greater than said threshold value;

d) comparing a timer value to a preselected sample period; and

,

e) if said timer value has reached said preselected sample period, comparing said counter value to a preset value and if said counter value is greater than said preset value said signal includes a valid pulse rate, wherein a portion of said detected signal is from at least one of the interfering transmitter, an electronic article surveillance tag response, or a combination thereof.

2. The method of claim 1, further comprising:

switching the pulsed electronic article surveillance system transmitter off;

repeating steps a) through e) and if said counter value is greater than said preset value said signal includes a valid pulse rate, wherein a portion of said signal is from an interfering transmitter, if said counter value is not greater than said preset value said signal does not include a valid pulse rate, wherein a portion of said signal is not from the interfering transmitter and resuming normal electronic article surveillance system operation.

3. The method of claim 2, further comprising:

switching the pulsed electronic article surveillance system transmitter off;

setting said threshold value just above a noise floor;

moving a line synchronization delay until said detected signal is below said threshold value;

moving said line synchronization delay until said detected signal is initially greater than said threshold value and wherein pulsed noise having a frequency higher than a preselected maximum transmitter pulse rate is ignored to detect a leading edge of the interfering transmitter pulse;

storing said line synchronization delay for said leading edge of the interfering transmitter pulse; and

,

synchronizing the pulsed electronic article surveillance system transmitter to said stored line synchronization delay and returning to normal operation.

4. The method of claim 2 further comprising generating a tags too close signal to indicate that said detected signal is due to an electronic article surveillance tag if said counter value is not greater than said preset value wherein said signal does not include a valid pulse rate, and wherein a portion of said signal is not from the interfering transmitter.

5. A system for automatic phase adjustment for synchronizing a pulsed electronic article surveillance system transmitter to an interfering transmitter, comprising:

means for detecting a signal in a preselected frequency range;

means for comparing said detected signal to a threshold value;

means for incrementing a counter value if said detected signal is greater than said threshold value;

means for comparing a timer value to a preselected sample period; and

,

means for comparing said counter value to a preset value, if said timer value has reached said preselected sample period, and if said counter value is greater than said preset value said detected signal includes a valid pulse rate, wherein a portion of said detected signal is from at least one of the interfering transmitter, an electronic article surveillance tag response, or a combination thereof.

6. The system of claim 5, further comprising:

means for switching the pulsed electronic article surveillance system transmitter off, and;

if said counter value is greater than said preset value said signal includes a valid pulse rate, wherein a portion of said signal is from the interfering transmitter, if said counter value is not greater than said preset value said signal does not include a valid pulse rate, wherein a portion of said signal is not from the interfering transmitter and normal electronic article surveillance system operation resumes.

7. The system of claim 6, further comprising:

means for setting said threshold value just above a noise floor, only after said pulsed electronic article surveillance system transmitter is switched off;

means for moving a line synchronization delay until said detected signal is below said threshold value;

means for moving said line synchronization delay until said detected signal is initially over said threshold value and wherein pulsed noise having a frequency higher than a preselected maximum transmitter pulse rate is ignored to detect a leading edge of the interfering transmitter pulse;

means for storing said line synchronization delay for said leading edge of the interfering transmitter pulse; and

,

means for synchronizing the pulsed electronic article surveillance system transmitter to said stored line synchronization delay and returning to normal operation.

8. The system of claim 6, further comprising means for generating a tags too close signal to indicate that said detected signal is due to an electronic article surveillance tag if said counter value is not greater than said preset value wherein said signal does not include a valid pulse rate, and wherein a portion of said signal is not from an interfering transmitter.

9. A method for determining if a signal detected by a pulsed electronic article surveillance system transmitter is due to an interfering transmitter or an electronic article surveillance tag, comprising:

a) detecting a signal in a preselected frequency range;

b) comparing said detected signal to a threshold value;

c) incrementing a counter value if said detected signal is greater than said threshold value;

d) comparing a timer value to a preselected sample period;

e) if said timer value has reached said preselected sample period, comparing said counter value to a preset value and if said counter value is greater than said preset value said signal includes a valid pulse rate, wherein a portion of said detected signal is from at least one of the interfering transmitter, an electronic article surveillance tag response, or a combination thereof;

f) switching the pulsed electronic article surveillance system transmitter off; and

,

g) repeating steps a) through e) and if said counter value is greater than said preset value said signal includes a valid pulse rate, wherein a portion of said signal is from an interfering transmitter, if said counter value is not greater than said preset value said signal does not include a valid pulse rate, wherein a portion of said signal is not from an interfering transmitter and then generating a tags too close signal to indicate that said detected signal is due to an electronic article surveillance tag, and resuming normal electronic article surveillance system operation.

10. A system for determining if a signal detected by a pulsed electronic article surveillance system transmitter is due to an interfering transmitter or an electronic article surveillance tag, comprising:

means for detecting a signal in a preselected frequency range;

means for comparing said detected signal to a threshold value;

means for incrementing a counter value if said detected signal is greater than said threshold value;

means for comparing a timer value to a preselected sample period;

means for comparing said counter value to a preset value, if said timer value has reached said preselected sample period, and if said counter value is greater than said preset value said detected signal includes a valid pulse rate, wherein a portion of said detected signal is from at least one of the interfering transmitter, an electronic article surveillance tag response, or a combination thereof; and

,

means for switching the pulsed electronic article surveillance system transmitter off; and

,

if said counter value is greater than said preset value said signal includes a valid pulse rate, wherein a portion of said signal is from the interfering transmitter, if said counter value is not greater than said preset value said signal does not include a valid pulse rate, wherein a portion of said signal is not from an interfering transmitter and further including means for generating a tags too close signal to indicate that said detected signal is due to an electronic article surveillance tag and returning to normal electronic article surveillance system operation.