EAS system antenna configuration for providing improved interrogation field distribution

• US 6,020,856 A
• Filed: 08/11/1997
• Issued: 02/01/2000
• Est. Priority Date: 05/30/1995
• Status: Expired due to Term

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Alicot, Jorge
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US08/909,036
• Time in Patent Office: 904 Days
• Field of Search: 343/742, 343/867, 340/551, 340/572
• US Class Current: 343/742
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: G08B 13/2477 Antenna or antenna activator circuit
• CPC Class Codes: H01Q 7/04 Screened antennas H01Q7/02, H01Q7/06 take precedence

Abstract

In an electronic article surveillance system, quadrature transmitting and receiving antennas are used to improve field distribution. A transmitting antenna arrangement includes first and second adjacent co-planar antenna loops and excitation circuitry for generating respective alternating currents in the first and second loops such that the respective alternating currents are 90° out of phase. In a receiving arrangement, respective signals received from two adjacent co-planar antenna loops are respectively phase-shifted by +45° and -45°, and the resulting phase-shifted signals are summed. A far-field cancelling transmitting antenna arrangement includes four loops operated at phases of 0°, 90°, 180° and 270° respectively. All four loops may be co-planar, with any bucking vertical segments being horizontally displaced from each other. Alternatively, the 0° and 180° loops may also be arranged in a common plane that is close to and parallel with another plane in which the 90° and 270° loops are arranged.

Claims

1. An antenna configuration for use with an EAS system comprising:

a first planar antenna arranged in a first plane, said first planar antenna including at least a first loop and a second loop arranged in said first plane, said first and second loops being substantially equal to each other in area;

a second planar antenna including at least two loops arranged in a second plane that is different from the first plane and is substantially parallel to the first plane, said first and second antennas substantially entirely overlapping in a direction normal to said planes, said second antenna including a third loop and a fourth loop, said third and fourth loops being substantially equal to each other in area and having a total area that is substantially equal to a total area of said first and second loops;

first excitation means for generating an alternating current in said first antenna, said first excitation means including means for generating respective alternating currents in said loops of said first antenna such that the respective alternating currents in said loops of said first antenna are about 180°

out of phase with each other; and

second excitation means for generating respective alternating currents in said loops of said second antenna, said respective alternating currents in said loops of said second antenna being about 180°

out of phase with each other and about 90°

out of phase with the alternating current in said first antenna.

2. An antenna configuration according to claim 1, wherein:

said first, second, third and fourth loops are all rectangular;

said first loop includes a first horizontal segment, a second segment extending downwardly vertically from a right end of said first segment, a third segment extending leftwardly and horizontally from a lower end of said second segment, and a fourth segment extending vertically to interconnect respective left ends of said first and third segments;

said second loop includes a fifth segment that extends horizontally in parallel and in proximity to said third segment of said first loop, a sixth segment extending downwardly vertically from a right end of said fifth segment, a seventh segment extending leftwardly and horizontally from a lower end of said sixth segment, and an eighth segment extending vertically to interconnect respective left ends of said fifth and seventh segments;

said third loop includes a ninth segment that extends horizontally, a tenth segment extending downwardly vertically from a right end of said ninth segment, an eleventh segment extending leftwardly and horizontally from a lower end of said tenth segment, and a twelfth segment extending vertically to interconnect respective left ends of said ninth and eleventh segments;

said fourth loop includes a thirteenth segment that extends vertically in parallel and in proximity to said twelfth segment of said third loop, a fourteenth segment extending leftwardly and horizontally from a lower end of said thirteenth segment, a fifteenth segment extending vertically upwardly from a left end of said fourteenth segment, and a sixteenth segment extending horizontally to interconnect respective upper ends of said thirteenth and fifteenth segments;

said first, third, fifth and seventh segments are all substantially equal in length;

said ninth, eleventh, fourteenth and sixteenth segments are all substantially equal in length to each other and have a length that is substantially one-half a length of said first, third, fifth and seventh segments;

said tenth, twelfth, thirteenth and fifteenth segments are all substantially equal in length to each other;

said second, fourth, sixth and eighth segments are all substantially equal in length to each other and have a length that is substantially one-half of a length of said tenth, twelfth, thirteenth and fifteenth segments;

said sixth segment is substantially vertically aligned with said second segment;

said eighth segment is substantially vertically aligned with said fourth segment;

said sixteenth segment is substantially horizontally aligned with said ninth segment; and

said fourteenth segment is substantially horizontally aligned with said eleventh segment.

3. An antenna configuration for use with an EAS system, comprising:

a first planar antenna arranged in a first plane, said first planar antenna including at least a first loop, a second and a third loop arranged in said first plane, said first and third loops having a total area substantially equal to an area of said second loop;

a second planar antenna including at least two loops arranged in a second plane that is different from the first plane and is substantially parallel to the first plane, said first and second antennas substantially entirely overlapping in a direction normal to said planes. said second antenna including a fourth loop and a fifth loop, said fourth and fifth loops being substantially equal to each other in area and having a total area that is substantially equal to a total area of said first, second and third loops;

first excitation means for generating an alternating current in said first antenna, said first excitation means generating respective alternating currents in said first, second and third loops such that the respective alternating currents in said first and third loops are in phase with each other, and the respective alternating current in said second loop is about 180°

out of phase with the respective alternating currents in said first and third loops; and

second excitation means for generating respective alternating currents in said loops of said second antenna, said respective alternating currents in said loops of said second antenna being about 180°

out of phase with each other and about 90°

out of phase with the alternating current in said first antenna.

4. An antenna configuration according to claim 3, wherein:

said first, second and third loops are all rectangular;

said fourth and fifth loops are both triangular;

said first loop includes a first horizontal segment, a second segment extending downwardly vertically from a right end of said first segment, a third segment extending leftwardly and horizontally from a lower end of said second segment, and a fourth segment extending vertically to interconnect respective left ends of said first and third segments;

said second loop includes a fifth segment that extends horizontally in parallel and in proximity to said third segment of said first loop, a sixth segment extending downwardly vertically from a right end of said fifth segment, a seventh segment extending leftwardly and horizontally from a lower end of said sixth segment, and an eighth segment extending vertically to interconnect respective left ends of said fifth and seventh segments;

said third loop includes a ninth segment that extends horizontally in parallel and in proximity to said seventh segment of said second loop, a tenth segment extending downwardly vertically from a right end of said ninth segment, an eleventh segment extending leftwardly and horizontally from a lower end of said tenth segment, and a twelfth segment extending vertically to interconnect respective left ends of said ninth and eleventh segments;

said fourth loop includes a thirteenth segment that extends vertically, a fourteenth segment that extends horizontally leftwardly from a lower end of said thirteenth segment, and a fifteenth segment that extends obliquely to interconnect a left end of said fourteenth segment and an upper end of said thirteenth segment;

said fifth loop includes a sixteenth segment extending obliquely and in parallel and in proximity to said fifteenth segment, a seventeenth segment extending vertically upwardly from a lower end of said sixteenth segment, and an eighteenth segment extending horizontally to interconnect respective upper ends of said sixteenth and seventeenth segments;

said first, third, fifth, seventh, ninth and eleventh segments are all substantially equal in length;

said second, fourth, tenth and twelfth segments are all substantially equal in length to each other;

said sixth and eighth segments are substantially equal in length to each other, each having a length that is twice a length of said second segment;

said thirteenth and seventeenth segments are substantially equal in length to each other, each having a length that is twice the length of said sixth segment;

said second, sixth and tenth segments are all substantially in vertical alignment with each other; and

said fourth, eighth and twelfth segments are all substantially in vertical alignment with each other.

5. An antenna for use in an EAS system, comprising:

first, second, third and fourth loops, all co-planar; and

excitation means for generating respective alternating currents in said first, second, third and fourth loops, such that the alternating current in said second loop is about 90°

out of phase with the alternating current in said first loop, and the alternating current in said fourth loop is about 180°

out of phase with the alternating current in said second loop;

said four loops collectively including a plurality of vertical segments and no two vertical segments in said antenna being vertically aligned with each other;

said first, second, third and fourth loops all being triangular;

said first loop including a first horizontal segment, a second segment extending obliquely downwardly and leftwardly from a right end of said first segment and having a lower end at a point displaced vertically downwardly from a mid-point of said first segment, and a third segment extending obliquely to interconnect said lower end of said second segment and a left end of said first segment;

said second loop including a fourth segment extending obliquely in parallel and in proximity to said second segment, a fifth segment extending vertically downwardly from an upper end of said fourth segment, and a sixth segment substantially aligned with said third segment and extending obliquely to interconnect respective lower ends of said fourth and fifth segments;

said third loop including a seventh segment extending obliquely in parallel and in proximity to said sixth segment, an eighth segment extending horizontally leftwardly from a lower end of said seventh segment, and a ninth segment substantially aligned with said fourth segment and extending obliquely to interconnect respective left ends of said seventh and eighth segments;

said fourth loop including a tenth segment substantially aligned with said second segment and extending obliquely in parallel and in proximity to said ninth segment, an eleventh segment extending vertically upwardly from a lower end of said tenth segment, and a twelfth segment substantially aligned with said seventh segment and extending obliquely in parallel and in proximity to said third segment to interconnect respective upper ends of said tenth and eleventh segments;

said first and eighth segments being substantially equal in length;

said fifth and eleventh segments being substantially equal in length to each other; and

said second, third, fourth, sixth, seventh, ninth, tenth and twelfth segments all being substantially equal in length to each other.

6. An antenna for use in an EAS system, comprising:

first, second, third and fourth loops, all co-planar; and

excitation means for generating respective alternating currents in said first, second, third and fourth loops, such that the alternating current in said second loop is about, 90°

out of phase with the alternating current in said first loop, and the alternating current in said fourth loop is about 180°

out of phase with the alternating current in said second loop;

said four loops collectively including a plurality of vertical segments and no two vertical segments in said antenna being vertically aligned with each other;

said first, second, third and fourth loops all being triangular;

said first loop including a first horizontal segment, a second segment extending obliquely downwardly and leftwardly from a right end of said first segment and having a lower end at a point displaced vertically downwardly from a mid-point of said first segment, and a third segment extending obliquely to interconnect said lower end of said second segment and a left end of said first segment;

said second loop including a fourth segment extending obliquely in parallel and in proximity to said second segment, a fifth segment extending vertically downwardly from an upper end of said fourth segment, and a sixth segment substantially aligned with said third segment and extending obliquely to interconnect respective lower ends of said fourth and fifth segments;

said fourth loop including a seventh segment extending obliquely in parallel and in proximity to said sixth segment, an eighth segment extending horizontally leftwardly from a lower end of said seventh segment, and a ninth segment substantially aligned with said fourth segment and extending obliquely to interconnect respective left ends of said seventh and eighth segments;

said third loop including a tenth segment substantially aligned with said second segment and extending obliquely in parallel and in proximity to said ninth segment, an eleventh segment extending vertically upwardly from a lower end of said tenth segment, and a twelfth segment substantially aligned with said seventh segment and expending obliquely in parallel and in proximity to said third segment to interconnect respective upper ends of said tenth and eleventh segments;

said first and eighth segments being substantially equal in length;

said fifth and eleventh segments being substantially equal in length to each other; and

said second, third, fourth, sixth, seventh, ninth, tenth and twelfth segments all being substantially equal in length to each other.

7. An antenna for use in an EAS system, comprising:

first, second, third and fourth loops, all co-planar; and

excitation means for generating respective alternating currents in said first, second, third and fourth loops, such that the alternating current in said second loop is about 90°

out of phase with the alternating current in said first loop, the alternating current in said third loop is about 180°

out of phase with the alternating current in said first loop, and the alternating current in said fourth loop is about 180°

out of phase with the alternating current in second loop;

said four loops collectively including at least one pair of vertical segments that are vertically aligned with each other; and

in each said pair of vertical segments respective alternating currents in the two vertical segments making up the pair of vertical segments are in a phase relationship substantially different from about 180°

out of phase.

8. An antenna according to claim 7, wherein said first, second, third and fourth loops are all triangular.

9. An antenna according to claim 8, wherein:

said first loop includes a first horizontal segment, a second segment extending downwardly vertically from a right end of said first segment, and a third segment extending obliquely to interconnect a lower end of said second segment and a left end of said first segment;

said second loop includes a fourth segment extending obliquely in parallel and in proximity to said third segment, a fifth segment extending vertically downwardly from an upper end of said fourth segment, and a sixth segment extending horizontally to interconnect respective lower ends of said fourth and fifth segments;

said third loop includes a seventh segment extending horizontally in parallel and in proximity to said sixth segment, an eighth segment vertically aligned with said fifth segment and extending downwardly vertically from a left end of said seventh segment, and a ninth segment extending obliquely to interconnect a lower end of said eighth segment and a right end of said seventh segment;

said fourth loop includes a tenth segment obliquely extending in parallel and in proximity to said ninth segment, an eleventh segment extending horizontally rightwardly from a lower end of said tenth segment, and a twelfth segment vertically aligned with said second segment and extending vertically to interconnect respective right ends of said ninth and tenth segments;

said first, sixth, seventh and eleventh segments are all substantially equal in length;

said second, fifth, eighth and twelfth segments are all substantially equal in length to each other; and

said third, fourth, ninth and tenth segments are all substantially equal in length to each other.

10. An antenna according to claim 7, wherein said first, second, third and fourth loops are all rectangular.

11. An antenna according to claim 10, wherein:

said first loop includes a first horizontal segment, a second segment extending downwardly vertically from a right end of said first segment, a third segment extending leftwardly and horizontally from a lower end of said second segment, and a fourth segment extending vertically to interconnect respective left ends of said first and third segments;

said second loop includes a fifth segment that extends horizontally in parallel and in proximity to said third segment of said first loop, a sixth segment vertically aligned with said second segment and extending downwardly vertically from a right end of said fifth segment, a seventh segment extending leftwardly and horizontally from a lower end of said sixth segment, and an eighth segment vertically aligned with said fourth segment and extending vertically to interconnect respective left ends of said fifth and seventh segments;

said third loop includes a ninth segment that extends vertically in parallel and in proximity to said sixth segment, a tenth segment that extends horizontally rightwardly from a lower end of said ninth segment, an eleventh segment that extends vertically upwardly from a right end of said tenth segment, and a twelfth segment that extends horizontally to interconnect respective upper ends of said ninth and eleventh segments,

said fourth loop includes a thirteenth segment that extends horizontally in parallel and in proximity to said twelfth segment, a fourteenth segment vertically aligned with said eleventh segment and extending vertically upwardly from a right end of said thirteenth segment, a fifteenth segment extending horizontally leftwardly from an upper end of said fourteenth segment, and a sixteenth segment vertically aligned with said ninth segment and extending vertically to interconnect respective left ends of said thirteenth and fifteenth segments;

said first, third, fifth, seventh, tenth, twelfth, thirteenth and fifteenth segments are all substantially equal in length; and

said second, fourth, sixth, eighth, ninth, eleventh, fourteenth and sixteenth segments are all substantially equal in length to each other.