CN106716506B

CN106716506B - System and method for adaptively controlling transmitter field

Info

Publication number: CN106716506B
Application number: CN201580052293.0A
Authority: CN
Inventors: A·S·伯格曼; M·A·索图
Original assignee: Tyco Fire And Safety Co ltd
Current assignee: Tyco Fire And Safety Co ltd
Priority date: 2014-08-05
Filing date: 2015-07-27
Publication date: 2021-09-03
Anticipated expiration: 2035-07-27
Also published as: CN106716506A; CA2961875C; EP3809383A1; EP3178075B1; AU2015298607B2; WO2016022313A1; AU2015298607A1; CA2961875A1; EP3809383B1; KR102531482B1; KR20170053622A; EP3178075A1

Abstract

A system (100) and method (600-800) for adaptively controlling a transmitter field in an electronic article surveillance ("EAS") detection system. The method comprises the following steps: detecting, by at least one first proximity sensor (108a, 108b), a presence of a first person located proximate to a pedestal (102a, 102b) of an EAS detection system; determining a first distance from a first proximity sensor to a first person; and using the first distance to adaptively control a transmitter field of the EAS detection system.

Description

System and method for adaptively controlling transmitter field

Technical Field

The present invention relates generally to electronic article surveillance ("EAS") detection systems. More particularly, the present invention relates to a system and method for adaptively controlling a transmitter of an EAS detection system.

Background

EAS detection systems generally comprise: an interrogation antenna for transmitting electromagnetic signals into an interrogation zone; a tag that responds to an interrogation signal in some known electromagnetic manner; an antenna for detecting a response of the marker; a signal analyzer for evaluating the signal generated by the detection antenna; and an alarm indicating the presence of a marker in the interrogation zone. The alarm may then be the basis for initiating one or more appropriate responses depending on the nature of the facility. Typically, the interrogation zone is near an exit of a facility (such as a retail store) and the tag may be attached to a commodity, such as a sales item or an inventory item.

One type of EAS detection system utilizes acousto-magnetic ("AM") markers. The overall operation of an AM EAS detection system is described in U.S. patent nos. 4510489 and 4510490, the disclosures of which are incorporated herein by reference. Detection of markers in AM EAS detection systems by pedestals disposed at the exit has been of particular interest for detecting only markers within the pedestal spacing. However, the interrogation field generated by the pedestal may extend beyond the intended detection region. For example, the first pedestal will generally include a main antenna field directed toward a detection area located between the first pedestal and the second pedestal. When an exciter signal is applied at the first pedestal, the first pedestal will generate an electromagnetic field of sufficient strength to excite the labels within the detection region. Similarly, the second pedestal will generally include an antenna having a main antenna field directed toward the detection area (and toward the first pedestal). The exciter signal applied at the second pedestal will also generate an electromagnetic field of sufficient strength to excite the markers within the detection zone. When the tag is excited in the detection area, the tag will generate an electromagnetic signal, which can be detected, typically by receiving the signal at antennas associated with the first and second bases.

Disclosure of Invention

The present invention relates to a system and method for implementing a transmitter field for use in an adaptive control EAS detection system. The method comprises the following steps: detecting, by at least one first proximity sensor, a presence of a first person located proximate to a pedestal of an EAS detection system; determining a first distance from a first proximity sensor to a first person; and using the first distance to adaptively control a transmitter field of the EAS detection system. The transmitter field is controlled by adjusting the transmit power of the first pedestal. When the first person moves out of the antenna field pattern, the transmit power of the first pedestal returns to its previous level.

In some cases, distance information related to a person located within the back field of the radiation pattern of the base's antenna should not be used to control the transmit power. As such, the method may also involve determining whether the first person is located within a back field of the radiation pattern of the antenna of the first pedestal. The first distance may be used for the adaptive control only if it is determined that the first person is not located within the back field of the radiation pattern of the antenna of the first pedestal. Alternatively, the first distance may only be used for said adaptive control if it is determined that the first person is located within the back field of the radiation pattern of the antenna of the first pedestal and if distance information associated with the person located in the back field should be used to control the transmit power of the pedestal.

In other cases, the range information from two or more sensors of an EAS detection system may be conflicting. As such, the method may further involve: determining a second distance from the second proximity sensor to the first person; and determining whether the first distance and the second distance are the same. If it is determined that the first distance and the second distance are the same, the first distance or the second distance is selected for controlling the transmission power. Alternatively, if it is determined that the first distance and the second distance are not the same, a minimum distance is selected from the first distance and the second distance. In this case, the minimum distance is used to control the transmit power.

In other cases, there may be two or more people located near the base. As such, the method may further involve: detecting a presence of a second person positioned proximate to a pedestal of the EAS detection system while the first person is positioned proximate to the pedestal; determining a second distance from the base to the second person; and determining whether the first distance and the second distance are the same. If it is determined that the first distance and the second distance are the same, the first distance or the second distance is selected for controlling the transmission power. Alternatively, if it is determined that the first distance and the second distance are not the same, a minimum distance is selected from the first distance and the second distance. (A) The minimum distance is used to control the transmission power if it is determined that the person associated with the minimum distance is not located within the back field of the radiation pattern of the antenna of the first pedestal, or (B) if it is determined that the person associated with the minimum distance is located within the back field of the radiation pattern of the antenna of the first pedestal and if the distance information associated with the person located in the back field should be used to control the transmission power of the pedestal.

Drawings

Embodiments will be described with reference to the following drawings, wherein like reference numerals represent like items throughout the several views, and wherein:

FIG. 1 is a side view of an EAS detection system.

Fig. 2 is a top view of the EAS detection system of fig. 1, which may be used to understand the EAS detection zone of the EAS detection system.

Fig. 3 and 4 are diagrams of a main field and a back field that may be used to understand an antenna used in the EAS detection system of fig. 1.

Fig. 5 is a diagram that may be used to understand the detection zones in the EAS detection system of fig. 1.

Fig. 6-8 each provide a flow chart of an exemplary method for adaptively controlling a transmitter field in an EAS detection system.

Fig. 9 is a block diagram of an arrangement of an EAS controller that may be used to understand the EAS detection system of fig. 1.

Detailed Description

It will be readily understood that the components of the embodiments as generally described herein, and illustrated in the figures, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the various embodiments, as represented in the figures, is not intended to limit the scope of the disclosure, as claimed, but is merely representative of various embodiments. While various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.

Reference in the specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. As used in this document, the term "including" means "including, but not limited to".

The present invention generally provides a system and method for adjusting EAS detection system power based on proximity information. In this regard, a sensor (e.g., an ultrasonic transducer) is mounted on a pedestal of the EAS detection system. These sensors may facilitate detection of a person positioned proximate to the base. Based on the detection, the transmitter power of the EAS detection system is attenuated such that the level is optimized for system performance. Indeed, the EAS detection system may experience power savings, reduced back field detection, and improved detection consistency as compared to conventional EAS detection systems.

Referring now to fig. 1 and 2, an exemplary architecture of an EAS detection system 100 is provided. Note that the present invention is described herein in terms of an AM EAS detection system. However, the method of the present invention may also be used with other types of EAS detection systems, including systems that use radio frequency ("RF") type tags and radio frequency identification ("RFID") EAS detection systems.

The EAS detection system 100 will be located adjacent to an entrance/exit 104 of a security facility (e.g., a retail store). The EAS detection system 100 uses specially designed EAS marker tags ("security tags") that are applied to store merchandise or other items stored within a security facility. The security tag may be deactivated or removed by authorized personnel at the security facility. For example, in a retail environment, the security tag may be removed by store personnel. When the EAS detection system 100 detects an active security tag 112 in an idealized representation of the EAS detection zone 108 near the entrance/exit, the EAS detection system will detect the presence of this security tag and will sound an alarm or generate some other suitable EAS response. Accordingly, EAS detection system 100 is arranged to detect and prevent unauthorized removal of merchandise or products from a controlled area.

The EAS detection system 100 includes a pair of

pedestals

102a, 102b, the

pedestals

102a, 102b being located a known distance apart (e.g., on opposite sides of the entrance/exit 104). Typically, the

pedestals

102a, 102b are stabilized and supported by the

base

106a, 106 b. Generally, each

pedestal

102a, 102b will include one or more antennas suitable for aiding in the detection of a particular EAS security tag, as described herein. For example, the base 102a may include at least one antenna 302, the antenna 302 being adapted to transmit or generate an electromagnetic exciter signal field and receive a response signal generated by a security tag in the detection region 108. In some embodiments, the same antenna may be used for both receive and transmit functions. Similarly, the base 102b may include at least one antenna 402, the antenna 402 being adapted to transmit or generate an electromagnetic exciter signal field and receive a response signal generated by a security tag in the detection region 108. The antennas provided in the

pedestals

102a, 102b may be of conventional conductive coil or wire loop design, as is commonly used in AM-type EAS pedestals. These antennas will sometimes be referred to herein as exciter coils. In some embodiments, a single antenna may be used in each pedestal. A single antenna is selectively coupled to the EAS receiver. The EAS transmitter operates in a time division multiplexed manner. However, as shown in fig. 1, it may be beneficial to include two antennas (or exciter coils) in each pedestal, with the upper antenna located above the lower antenna.

The antennas located in the

pedestals

102a, 102b are electrically coupled to the system controller 110. System controller 110 controls the operation of EAS detection system 100 to perform EAS functions as described herein. The system controller 110 may be located within the

base

106a, 106b of one of the

pedestals

102a, 102b, or may be located within a separate chassis at a location proximate to the pedestals. For example, the system controller 110 may be located in a ceiling directly above the

bases

102a, 102b or adjacent to the

bases

102a, 102 b.

As described above, the EAS detection system includes an AM-type EAS detection system. As such, each antenna is used to generate an electromagnetic ("EM") field that serves as a security tag exciter signal. The security tag exciter signal causes mechanical oscillation of a strip (e.g., a strip formed of a magnetostrictive or ferromagnetic amorphous metal) contained in the security tag within the detection region 108. Due to the stimulus signal, the security tag will resonate and mechanically vibrate due to the effects of magnetostriction. The vibration will last for a short time after the stimulation signal is terminated. The vibration of the strip causes its magnetic field to change, which may induce an AC signal in the receiver antenna. The sensed signal is used to indicate the presence of a strip within the detection zone 108. As described above, the same antenna contained in the

pedestals

102a, 102b can be used as both a transmitting antenna and a receiving antenna. Thus, the antenna in each of the

pedestals

102a, 102b can be used in several different modes to detect the security tag exciter signal. These modes will be described in more detail below.

Referring now to fig. 3 and 4, exemplary

antenna field patterns

300, 400 of the

antennas

302, 402 contained in the

pedestals

102a, 102b are shown. As is known in the art, an antenna radiation pattern is a graphical representation of the radiation (or reception) properties of a given antenna as a function of spacing. The properties of the antenna are the same in the transmit and receive modes of operation. As such, the illustrated antenna radiation patterns are applicable to both transmit and receive operations as described herein. The exemplary

antenna field patterns

300, 400 shown in fig. 3-4 are azimuth plane patterns, representing antenna patterns in the x, y coordinate plane. The orientation pattern is represented in polar form and is sufficient for understanding the inventive arrangement. The azimuth antenna field patterns shown in figures 3-4 are a useful way to visualize the direction in which the

antennas

302, 402 will transmit and receive signals at a particular power level.

The antenna field pattern 300 shown in fig. 3 includes a peak at

Main lobe 304 and peak at

The back field lobe 306. In contrast, the antenna field pattern 400 shown in fig. 4 includes a peak at

Main lobe 404 and peak at

The back field lobe 406. In EAS detection system 100, each

pedestal

102a, 102b is positioned such that the main lobe of the antenna contained therein is directed into detection region 108. Thus, a pair of

pedestals

102a, 102b in the EAS detection system 100 will create an overlap in the

antenna field patterns

300, 400, as shown in fig. 5. Note that the

antenna field patterns

300, 400 shown in fig. 5 are scaled for purposes of understanding the present invention. In particular, the pattern shows the outer boundaries or limits of the area in which an exciter signal of a particular amplitude applied to the

antennas

302, 402 will produce a detectable response in an EAS security tag. It should be understood, however, that a security tag within the confines of at least one

antenna field pattern

300, 400 will produce a detectable response when stimulated by an exciter signal.

The overlapping

antenna field patterns

300, 400 in fig. 5 will include a region a in which the

main lobes

304, 404 overlap. However, it can be observed in fig. 5 that the main lobe of each pedestal and the back field lobe associated with the other pedestals may also have some overlap. For example, it can be observed that in region B, the main lobe 404 overlaps the back field lobe 306. Similarly, in region C, the main lobe 304 overlaps the back field lobe 406. The area a between

pedestals

102a, 102b defines an EAS detection zone 108 where active security tags should cause the EAS detection system 100 to generate an alarm response in the detection zone 108. The security tags in region a are stimulated by the energy associated with the exciter signal within the

main lobes

304, 404 and will produce a response that can be detected at each antenna. The response produced by the security tags in zone a is detected within the main lobe of each antenna and processed in the system controller 110. Note that security tags in either region B or C will also be excited by the

antennas

302, 402. The response signals generated by the security tags in these areas B and C will also be received at one or both of the antennas. This response signal is referred to herein as the "security tag signal".

Referring again to fig. 1-2, a plurality of proximity sensors (e.g., ultrasonic transducers) 108a, 108b are beneficially mounted on each

base

102a or 102 b. Proximity sensors and ultrasonic transducers are well known in the art and will not be described herein. Additionally, it should be understood that each

proximity sensor

108a, 108b is generally configured to detect the presence of a person and/or object located on a given side of the respective pedestal and his/her/its distance from the pedestal.

Thus, the

proximity sensors

108a, 108b are arranged to point to both the top and bottom fields of each

respective pedestal

102a, 102 b. As such, the first proximity sensor points in a first direction, shown by arrow 110, and thus detects a person located in the back field of the respective pedestal. The second proximity sensor points in a second opposite direction, shown by arrow 112, and thus detects a person located in the forecourt of the respective pedestal.

In the case of an ultrasound transducer, each proximity sensor: generating high-frequency sound waves; transmitting a high frequency sound wave in a given direction; and receiving echo signals from people and/or objects within the range of the transmitted high frequency sound waves. Next, the system controller 110 determines a time interval between a first time that the respective high frequency acoustic wave is transmitted from the proximity sensor and a second time that the echo signal is received by the proximity sensor. The system controller 110 then uses the time interval to determine the distance from the respective base to the person/object based on the previously determined time interval. The determined distance is then used individually and/or independently for each pedestal to control EAS transmitter power. After the person moves a certain distance from the pedestal (e.g., a sufficient distance so as to no longer be within the interrogation zone), the EAS transmitter power returns to its original level.

By controlling the EAS transmitter power of the pedestal, the size of the pedestal's antenna field pattern is dynamically adjusted based on proximity information about a person located close to the pedestal. Since the EAS transmitter power of each pedestal is adjusted independently of the EAS transmitter power of the other pedestal, the antenna field patterns of the two pedestals may be the same or different at any given time. For example, let us assume that the person is located closer to the base 102a than to the base 102 b. In this case, the antenna field pattern of the pedestal 102a is adjusted to reduce its overall size by an amount greater than that of the antenna field pattern of the pedestal 102 b.

In some cases, distance information associated with people located within the backyard is ignored, i.e., not used to control EAS transmitter power. As such, only the distance information associated with the person located between the

pedestals

102a, 102b is used to adaptively control the antenna field patterns of the two

pedestals

102a, 102 b. In other cases, this is not the case, and the distance information associated with the people located within the fore and aft fields is used to control the strength of the transmitter field.

In those and other cases, the

sensors

108a and 108b may generate conflicting information regarding the distance of a particular person relative to a given

base

102a or 102 b. For example, the proximity sensor 108a generates information indicating that the person is 3 feet from the base 102 a. Conversely, the proximity sensor 108b generates information indicating that the person is 2 feet from the base 102 a. As such, the information generated by the two proximity sensors is conflicting. Thus, the transmitter power of the base 102a is adjusted based on the information generated by the proximity sensor 108b rather than the information generated by the proximity sensor 108a, i.e., based on the sensor information indicating the minimum distance to the base 102 a.

In most cases, only one person with an active security tag will be located near the

pedestals

102a, 102 b. However, there are some instances where two or more persons possessing active security tags are located proximate to the

pedestals

102a, 102 b. In this case, it is determined which person is closer to a given base. The distance information associated with that person (i.e., the closest person) is then used to adaptively control the transmitter field for a given pedestal.

In all cases, the antenna field patterns of

pedestals

102a and 102b are selectively reduced to obtain the following advantages: (1) power is saved; (2) reducing back field detection; and/or (3) improve detection consistency. With respect to advantage (1), in some cases (e.g., when a person is located close to the base), power savings are achieved by simply reducing transmitter power. For advantage (2), reduced backfield detection is achieved by ignoring security tag signals associated with people located within the backfield. With respect to advantage (3), it should be appreciated that when the security tag is in close proximity to the pedestal, the security tag signal may not be detected because the transmitter field is relatively strong at that location. The relatively strong transmitter field causes the amplitude of the security tag signal to exceed a given threshold and thus be deemed by the system 100 as not constituting a detected security tag signal. By reducing the antenna field pattern and/or the transmitter field, the transmitter field strength near the transmitter is reduced, thereby also reducing the amplitude of the security tag signal. In effect, the amplitude of the security tag signal falls below the threshold. Thus, the security tag signal is properly detected within the system 100.

Referring now to fig. 6, a flow diagram of an exemplary method 600 for adaptively controlling a transmitter field in an EAS detection system is provided. The method 600 begins at step 602 and proceeds to step 604. In step 604, the presence of a person positioned proximate to a pedestal (e.g.,

pedestal

102a or 102b of fig. 1) of an EAS detection system is detected. Next, the distance from the base to the person is determined, as shown in step 606.

Thereafter, it is determined whether or not a person is present in the back field of the radiation pattern of the antenna of the base. If no one is located in the backyard [ 608: no ], step 610 is performed. Step 610 involves using the determined distance to adaptively control the transmitter field for the transmitter of the pedestal such that the overall size of the antenna field pattern is reduced. Method 600 then continues with step 618. Step 618 involves detecting when a person has moved out of the antenna pattern. In response to this detection, step 620 is performed, in step 620, the base's transmit power level is reset, i.e., returned to its initial value. Subsequently, step 622 is performed, and in step 622, the method 600 returns to step 604.

If a person is located within the backyard [ 608: yes ], decision step 612 is performed to determine whether the distance information associated with the person in the back field should be used to control transmitter power. If the distance information associated with the person in the back field should not be used to control the transmitter power [ 612: no ], step 614 is performed, and in step 614, the method 600 returns to step 604. Conversely, if the distance information associated with the person in the back field should be used to control the transmitter power [ 612: yes ], then the determined distance is used to adaptively control the transmitter field for the base's transmitter such that the overall size of the antenna field pattern is reduced, as shown at step 616. Next, step 618 involves detecting when the person has moved out of the antenna pattern. In response to this detection, step 620 is performed, in step 620, the base's transmit power level is reset, i.e., returned to its initial value. Subsequently, step 622 is performed, and in step 622, the method 600 returns to step 604.

Referring now to fig. 7, a flow diagram of an exemplary method 700 for adaptively controlling a transmitter field in an EAS detection system is provided. Method 700 illustrates an exemplary process when two proximity sensors provide the same or conflicting distance measurements. For example, in the case of conflicting distance measurements, the first proximity sensor indicates that the person is 2 feet from the base. The second proximity sensor indicates that the person is 3 feet from the base. The following process describes how conflicting distance information may be handled in system 100.

As shown in fig. 7, the method 700 begins at step 702 and continues with step 704. In step 704, detection is performed by at least two proximity sensors of the EAS detection system. More specifically, each proximity sensor detects the presence of a person positioned proximate to a pedestal of the EAS detection system. Then, the distance from each sensor to the detected person is determined in step 706. Thereafter, a decision step 708 is performed to determine whether the two distances are the same.

If the two distances are the same [ 708: yes ], then either of these two determined distances is selected. Conversely, if the two distances are not the same [ 708: no ], then the determined distance having the minimum value of the two determined distances is selected, as shown in step 712. Upon completion of

steps

710 or 712, a determination is made as to whether the person is located within the back field of the radiation pattern of the antenna of the base.

If the detected person is not located in the back field [ 714: no ], then step 716 is performed. Step 716 involves using the selected determined distance to adaptively control the transmitter field for the transmitter of the EAS detection system such that the overall size of the antenna field pattern is reduced. Thereafter, in step 724, it is detected when the person has moved out of the antenna field pattern. When such detection is made, the base's transmit power is increased to its initial value, as shown at step 726. Subsequently, step 728 is performed, and in step 728, method 700 returns to step 704.

If the detected person is located within the backyard [ 714: yes ], then in step 718 it is determined whether the distance information associated with the person located in the back field should be used to control the transmitter power. If the distance information should not be used to control transmitter power [ 720: no ], then the method 700 returns to step 704, as shown in step 720. Conversely, if the distance information should be used to control the transmitter power [ 720: yes ], then step 722 is performed, and in step 722 the selected determined distance is used to adaptively control the base's transmitter field such that the overall size of the antenna field pattern is reduced. In a next step 724, it is detected when the person moves out of the antenna field pattern. When such detection is made, the base's transmit power is increased to its initial value, as shown at step 726. Subsequently, step 728 is performed, and in step 728, method 700 returns to step 704.

Referring now to fig. 8, a flow diagram of an exemplary method 800 for adaptively controlling a transmitter field in an EAS detection system is provided. Method 800 illustrates an exemplary process when performing a detection indicating that a location of two or more individuals is proximate to a base. For example, a first proximity sensor detects the presence of a first person, while a second proximity sensor detects the presence of a second person. The following method 800 describes how the system 100 may handle such a scenario: when two people are located in the back field, two people are located in the front field, and/or only one person is located in the back field or the front field.

As shown in fig. 8, method 800 begins at step 802 and continues with step 804. Step 804 involves detecting the presence of at least two persons located proximate to a pedestal (e.g.,

pedestal

102a or 102b of fig. 1) of an EAS detection system (e.g., system 100 of fig. 1). In a next step 806, the distance from the base to each detected person is determined. If the determined distances are the same [ 808: yes ], then either of the two determined distances is selected in step 810. If the determined distances are not the same [ 808: no ], the determined distance having the minimum value of the two determined distances is selected in step 812. Upon completion of either

step

810 or 812, the method 800 continues with step 814-828.

In decision step 814, it is determined whether the person associated with the selected determined distance is located within the back field of the radiation pattern of the antenna of the pedestal. If the person is not located within the backyard [ 814: no ], the selected determined distance is used to adaptively control the transmitter field for the base's transmitter such that the overall size of the antenna field pattern is reduced. Subsequently, step 824 is performed, detecting when the person moves out of the antenna field pattern in step 824. Upon this detection, the base's transmit power is increased to its initial value, as shown in step 826. Thereafter, step 828 is performed, and in step 828, the method 800 returns to step 804.

If a person is located within the backyard [ 814: yes ], decision step 818 is performed, and in decision step 818, it is determined whether the distance information associated with the person located in the back field should be used to control the transmitter power. If the distance information should not be used in the manner described [ 818: no ], then step 820 is performed. In step 820, another determined distance information (i.e., another detected person's determined distance information) is selected. Thereafter, the method 800 returns to step 814, as shown at step 821.

If the distance information should be used in the manner [ 818: yes ], then step 822 is performed, in which step 822 the selected determined distance information is used to adaptively control the transmitter field for the base's transmitter such that the overall size of the antenna field pattern is reduced. In a next step 824, it is detected when the person has moved out of the antenna field pattern. Upon this detection, the base's transmit power is increased to its initial value, as shown in step 826. Thereafter, step 828 is performed, and in step 828, the method 800 returns to step 804.

Referring now to fig. 9, a block diagram is provided that may be used to understand the arrangement of the system controller 110. The system controller includes a processor 916, such as a microcontroller or central processing unit ("CPU"). The system controller also includes a computer-readable storage medium, such as the memory 918, having stored thereon one or more sets of instructions (e.g., software code) configured to implement one or more methods, processes, or functions described herein. The instructions (i.e., computer software) may include an EAS detection module 920 to facilitate EAS detection and to perform methods of selectively issuing an alarm based on the detected location of an EAS security tag, as described herein. The instructions may also include a person detection module 950 to facilitate detecting a person positioned proximate to the base, determining a distance from the base to the person, and adaptively controlling the transmitter field based on the determined distance. The instructions may also reside, completely or at least partially, within the processor 916 during execution thereof.

The system also includes at least one EAS transceiver 908, the EAS transceiver 908 including a transmitter circuit 910 and a receiver circuit 912. The transmitter and receiver circuits are electrically coupled to the antenna 302 and the antenna 402. A suitable multiplexing arrangement may be provided to facilitate both receive and transmit operations using a single antenna (e.g., antenna 302 or 402). The transmit operation may occur simultaneously at the

antennas

302, 402, after which the receive operation may occur simultaneously at each antenna to listen for the tag tags that have been energized. Alternatively, the transmission operation may be selectively controlled as described herein such that only one antenna is active when transmitting the security tag exciter signal for the purpose of executing the various algorithms described herein. The

antennas

302, 402 may include upper and lower antennas similar to those shown and described with respect to fig. 1. The input exciter signals applied to the upper and lower antennas may be controlled by the transmitter circuitry 910 or processor 916 such that the upper and lower antennas operate in a phase-assisted or anti-phase configuration as desired.

Additional components of system controller 110 may include a communication interface 924, communication interface 924 configured to facilitate wired and/or wireless communication from system controller 110 to a remotely located EAS system server. The system controller may further include: a real-time clock for timing purposes; an alarm 926 (e.g., an audible alarm, a visual alarm, or both) may be activated when an active EAS security tag is detected within the EAS detection zone 108. A power supply 928 provides the necessary power to the various components of the system controller 110. Electrical connections from the power supply to the various system components have been omitted from fig. 9 to avoid obscuring the invention.

Those skilled in the art will appreciate that the system controller architecture illustrated in FIG. 9 represents one possible example of a system architecture that may be used with the present invention. However, the invention is not limited in this regard and any other suitable architecture may be used in any case without limitation. Dedicated hardware implementations including, but not limited to, application specific integrated circuits, programmable logic arrays and other hardware devices can similarly be constructed to implement the methods described herein. It should be understood that the apparatus and systems of various inventive embodiments broadly include a variety of electronic and computer systems. Some embodiments may implement functions in two or more specific interconnected hardware modules or devices with related control and data signals communicated between and among the modules, or as portions of an application-specific integrated circuit. Thus, the exemplary system is applicable to software, firmware, and hardware implementations.

Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Thus, the breadth and scope of the present invention should not be limited by any of the above-described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.

Claims

1. A method for adaptively controlling a transmitter field in an Electronic Article Surveillance (EAS) detection system, comprising:

detecting, by at least one first proximity sensor, a presence of a first person located proximate to a pedestal of the EAS detection system;

determining, by the first proximity sensor, a first distance from the base to the first person;

determining, by a second proximity sensor, a second distance from the base to the first person or a second person;

comparing the first distance to the second distance; and

using the results of the comparison to adaptively control the transmitter field of the EAS detection system, wherein the transmitter field is controlled to ensure that the amplitude of a signal produced by a tag located proximate to the pedestal when excited by the transmitter field does not exceed a threshold value.

2. The method of claim 1, further comprising: determining whether the first person is located in a back field of a radiation pattern of an antenna of the pedestal.

3. The method of claim 2, further comprising: using the result of the comparison to adaptively control the transmitter field of the EAS detection system only if it is determined that the first person is not located in the back field of the radiation pattern of the antenna of the pedestal.

4. The method of claim 1, further comprising: when the first person moves out of the antenna field pattern, the transmit power of the pedestal is returned to the previous level.

5. A method for adaptively controlling a transmitter field in an Electronic Article Surveillance (EAS) detection system, comprising:

determining, by the first proximity sensor, a first distance from the base to the first person; and

determining whether the first person is located in a back field of a radiation pattern of an antenna of the pedestal; and

using the first distance to adaptively control the transmitter field of the EAS detection system if it is determined that the first person is located in the back field of the radiation pattern of the antenna of the pedestal and if distance information associated with a person located in the back field should be used to control transmit power of the pedestal.

6. A method for adaptively controlling a transmitter field in an Electronic Article Surveillance (EAS) detection system, comprising:

determining, by a second proximity sensor, a second distance from the base to the first person;

determining whether the first distance and the second distance are the same;

selecting either one of the first distance and the second distance for controlling transmission power if it is determined that the first distance and the second distance are the same, or selecting a minimum distance from the first distance and the second distance if it is determined that the first distance and the second distance are not the same; and

adaptively controlling the transmitter field of the EAS detection system using the previously selected minimum distance, the first distance, or the second distance, wherein the transmitter field is controlled to ensure that an amplitude of a signal produced by a tag located proximate to the pedestal when excited by the transmitter field does not exceed a threshold value.

7. The method of claim 6, further comprising:

(A) if it is determined that the person associated with the minimum distance is not located in the back field of the radiation pattern of the antenna of the pedestal, or

(B) If it is determined that the person associated with the minimum distance is located in the back field of the radiation pattern of the antenna of the pedestal, and if distance information associated with the person located in the back field should be used to control the transmit power of the pedestal,

the minimum distance is used to control the transmit power.

8. A method for adaptively controlling a transmitter field in an Electronic Article Surveillance (EAS) detection system, comprising:

detecting a presence of a second person located proximate to a pedestal of the EAS detection system when the first person is located proximate to the pedestal;

determining a second distance from the base to the second person; and

determining that the first distance and the second distance are not the same;

selecting a minimum distance from the first distance and the second distance; and

the minimum distance is used to adaptively control a transmitter field of the EAS detection system, wherein the transmitter field is controlled to ensure that an amplitude of a signal produced by a tag located proximate to the pedestal when excited by the transmitter field does not exceed a threshold value.

9. An Electronic Article Surveillance (EAS) detection system, comprising:

at least one proximity sensor for detecting the presence of a first person positioned proximate to a pedestal of the EAS detection system; and

system controller for

Determining a first distance from the base to the first person by a first proximity sensor,

determining a second distance from the base to a second person by a second proximity sensor,

comparing the first distance with the second distance, and

using the result of the comparison to adaptively control a transmitter field of the EAS detection system, wherein the transmitter field is controlled to ensure that an amplitude of a signal produced by a tag located proximate to the pedestal when excited by the transmitter field does not exceed a threshold value.

10. The EAS detection system according to claim 9, wherein the system controller further determines whether the first person is located in a back field of a radiation pattern of an antenna of the pedestal.

11. The EAS detection system according to claim 10, wherein the system controller uses the first distance to adaptively control the transmitter field only if it is determined that the first person is not located in the back field of the radiation pattern of the antenna of the pedestal.

12. The EAS detection system according to claim 9, wherein the system controller further returns the pedestal's transmit power to a previous level when the first person moves out of the antenna field pattern.

13. An Electronic Article Surveillance (EAS) detection system, comprising:

a system controller to determine a first distance from the pedestal to the first person via a first proximity sensor and to use the first distance to adaptively control a transmitter field of the EAS detection system;

wherein the system controller further determines whether the first person is located in a back field of a radiation pattern of an antenna of the pedestal; and is

Wherein the system controller uses the first distance to adaptively control the transmitter field if it is determined that the first person is located in the back field of the radiation pattern of the antenna of the pedestal and if distance information associated with a person located in the back field should be used to control transmit power of the pedestal.

14. An Electronic Article Surveillance (EAS) detection system, comprising:

system controller for

Determining, by a first proximity sensor, a first distance from the base to the first person;

determining whether the first distance and the second distance are the same;

selecting either the first distance or the second distance for controlling transmit power if it is determined that the first distance and the second distance are the same, or selecting a minimum distance from the first distance and the second distance if it is determined that the first distance and the second distance are not the same; and is

Adaptively controlling a transmitter field of the EAS detection system using the previously selected minimum distance, the first distance, or the second distance, wherein the transmitter field is controlled to ensure that an amplitude of a signal produced by a tag located proximate to the pedestal when excited by the transmitter field does not exceed a threshold value.

15. An Electronic Article Surveillance (EAS) detection system, comprising:

system controller for

determining a second distance from the base to the second person; and is

Determining that the first distance and the second distance are the same;

16. The EAS detection system according to claim 15, wherein

the minimum distance is used to control the transmit power.