Abstract:
An radio frequency identification (“RFID”) system and RFID tag that include a substrate body having a surface where the substrate body defines a plane of the tag, an RFID integrated circuit disposed on the surface of the substrate body, and an antenna that has an antenna pattern, which is disposed on the substrate body and in electrical communication with the RFID integrated circuit, the antenna generating a radiation pattern with maximum gain along an axis that is substantially coplanar with the tag. The antenna can include a first antenna portion and a second antenna portion, the first antenna portion having a first antenna end and a second antenna end, the first antenna end of the first antenna portion in electrical communication with the RFID integrated circuit and the first antenna portion forming an antenna pattern in a counterclockwise direction, and the second antenna portion having a first antenna end and a second antenna end, the first antenna end of the second antenna portion in electrical communication with the RFID integrated circuit and the second antenna portion forming an antenna pattern in a clockwise direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     n/a 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     n/a 
     FIELD OF THE INVENTION 
     The present invention relates to tag antennas, and, in particular, to tag antennas for radio frequency identification (“RFID”) systems. 
     BACKGROUND OF THE INVENTION 
     Accurately monitoring of the location and flow of the objects associated with inventory, product manufacturing, merchandising, and related operations is challenging. There is a continuing need to determine the location of these objects and to track relevant information about the objects. A tag, marker or label device suitably configured to be associated with any of a variety of objects, including goods, items, persons, or animals, or substantially any moving or stationary and animate or inanimate object, which facilitates location and data tracking, can be used. One such tag tracking system is an electronic identification system, such as RFID. RFID tags are affixed to, connected to, or in some way associated with an object for the purpose of tracking the object, and storing and retrieving information about the object. 
     The RFID tag stores data associated with the object. An RFID reader may scan for RFID tags by transmitting an interrogation signal at a known frequency. The RFID tags may respond to the interrogation signal with a response containing, for example, data associated with the object or an RFID tag ID. The RFID reader detects the response signal and decodes the data or the RFID tag ID. The RFID reader may be a handheld reader, or a fixed reader by which items carrying an RFID tag pass. A fixed reader may be configured as an antenna located in a pedestal similar to an electronic article surveillance (“EAS”) system. 
     Antennas collect and emit energy in the form of electromagnetic waves. The units for this transfer take the form of power-per-unit area. Many tags for use in such tag detection systems have a single favored orientation with respect to the stimulating field where they exhibit a maximum response, i.e., they are directional. Most tags are somewhat rectangular in shape and are variations of a dipole antenna, with a high length-to-width ratio. These tags give a maximum response when oriented within an incident field orthogonal to the long axis of the tag. This property is commonly referred to as “read orientation sensitivity”. 
     For example,  FIG. 1  illustrates an example of a RFID tag  100  with an antenna  102  disposed upon substrate  104 . Substrate  104  is substantially rectangular in shape. The antenna  102  comprises multiple antenna portions, i.e., antenna  102  has a first antenna portion  106  and a second antenna portion  108 . The first antenna portion  106  is connected to a first side  112 A of lead frame  112 . Second antenna portion  108  may be connected to a second side  112 B of lead frame  112 . RFID chip  110  may be connected to lead frame  112  by ultrasonically bonding lead frame  112  to the conductive pads on RFID chip  110 . RFID chip  110  and lead frame  112  are placed directly in the geometric center of the dielectric substrate material of substrate  104 . The ends of lead frame  112  can be physically and electrically bonded to the foil antenna pattern of antenna  102 . The RFID chip also can be bonded directly to antenna  102  at the conductive pads by use of conductive adhesive to eliminate the need for lead frame  112 . 
     The first antenna portion  106  has a first antenna end  106 A and a second antenna end  106 B. Similarly, second antenna portion  108  has a first antenna end  108 A and a second antenna end  108 B. The first antenna end  106 A of first antenna portion  106  is connected to lead frame  112 A. First antenna portion  106  is disposed on substrate  104  and forms an inwardly spiral pattern from RFID chip  110  in a first direction, with second antenna end  106 B to terminate on the inner loop of the inwardly spiral pattern on one half of the substrate  104 . Similarly, first antenna end  108 A of second antenna portion  108  is connected to lead frame  112 B. Second antenna portion  108  is disposed on substrate  104  to form an inwardly spiral pattern from RFID chip  110  in a second direction, with second antenna end  108 B to terminate on the inner loop of the inwardly spiral pattern on the other half of the substrate  104 . As illustrated in  FIG. 1 , the two clockwise spiral sections  106 ,  108  of antenna  102  basically are rotationally symmetrical with respect to each other. The RFID tag  100  generates a radiation pattern  200  ( FIG. 2 ) similar to the radiation pattern of a conventional dipole antenna. 
     The RFID tag  100  receives and emits best when perpendicular (e.g., along the z-axis) to its y-axis and not at all along that y-axis (also referred to as the “dipole axis”), as illustrated by the radiation pattern  200  graph of  FIG. 2 . The dead area in the radiation pattern  200  of the antenna  102  is referred to as a null  202 . Antenna directivity is important for RFID tags because if the tag  100  is oriented where its null  202  is pointed at the tag reader, the tag  100  receives no power for excitation and therefore is not read. In general, the radiation pattern describes the sensitivity of the receiving antenna to the direction of travel or the propagation of an electromagnetic (“EM”) wave. Since the EM wave is a transverse wave, the E-field component of the EM wave is perpendicular to the direction of the wave propagation. 
     Another situation that causes additional null regions in the radiation pattern  200  of the tag antenna  102  is when the RFID tag  100  is applied to a conductive surface, e.g., a metal surface. In order to couple energy into a “dipole-like” antenna, an excitation field (“E-field”) parallel to the length of the dipole-like antenna that has the proper frequency is required. The conductive nature of the metal dictates that the tangential e-field, which is aligned with length of the dipole, will be zero on the metal surface. This effect prevents coupling of energy into the RFID tag  100 , which causes a full or partial degradation of the detection performance of the RFID tag  100 . 
     Once removed from the surface of the metal, the electric field can be non-zero. Therefore, a dielectric spacer, which provides separation between the dipole antenna and the metal surface, enables some degree of an excitation field reaching the RFID tag  100 . However, a large spacer, e.g., larger than ten millimeters, is required even for ultra-high frequency (“UHF”) RFID tags to regain comparable exposure to the excitation field, and thus making the packaging and application impractical. In addition, the typical dielectric spacer is relatively expensive. 
     In view of the above, it is desirable to provide an RFID device having a radiation pattern that is minimally affected by a conductive surface, such as a metal surface, EAS tag, etc. 
     SUMMARY OF THE INVENTION 
     The present invention advantageously provides a radio frequency identification (“RFID”) system and RFID tag for operation with conductive elements. 
     In accordance with one aspect, the present invention provides an RFID tag for use with conductive elements that includes a substrate body having a surface and defining a plane of the tag. An RFID integrated circuit is disposed on the surface of the substrate body. An antenna that has an antenna pattern is disposed on the substrate body and is in electrical communication with the RFID integrated circuit. The antenna generates a radiation pattern with maximum gain along an axis that is substantially coplanar with the tag. The antenna can include a first antenna portion and a second antenna portion. The first antenna portion has a first antenna end and a second antenna end. The first antenna end of the first portion is in electrical communication with the RFID integrated circuit. The first antenna portion forms an antenna pattern in a counterclockwise direction. The second antenna portion has a first antenna end and a second antenna end. The first antenna end of the second antenna portion in electrical communication with the RFID integrated circuit. The second antenna portion forms an antenna pattern in a clockwise direction. 
     In accordance with another aspect, the present invention provides an RFID system for use with conductive elements that includes a RFID reader that generates interrogation signals, and a security tag to receive the interrogation signal and transmit a response signal. The security tag includes a substrate body having a surface and defining a plane of the tag. An RFID integrated circuit is disposed on the surface of the substrate body. An antenna that has an antenna pattern is disposed on the substrate body and is in electrical communication with the RFID integrated circuit. The antenna arranged to generate a radiation pattern with maximum gain along an axis that is substantially coplanar with the tag. 
     In accordance with another aspect, the present invention provides an RFID tag for use with conductive elements that includes a substrate body having a surface and defining a plane of the tag, an RFID integrated circuit disposed on the surface of the substrate body, a conductive element, the conductive element proximate the substrate body, and an antenna that has an antenna pattern. The antenna is disposed on the substrate body and in electrical communication with the RFID integrated circuit, the antenna arranged to generate a radiation pattern with maximum gain along an axis that is substantially coplanar with the tag. 
     Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The aspects of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a diagram of a conventional RFID tag; 
         FIG. 2  is a diagram illustrating an example of a three-dimensional radiation pattern of the conventional tag antenna of  FIG. 1 ; 
         FIG. 3  is a diagram of a RFID system constructed in accordance with the principles of the present invention; 
         FIG. 4  is a diagram of another embodiment of a RFID system constructed in accordance with the principles of the present invention; 
         FIG. 5  is a diagram of an exemplary tag having an antenna constructed in accordance with the principles of the present invention; 
         FIG. 6  is a diagram illustrating an example of a three-dimensional radiation pattern of the antenna of the tag of  FIG. 5  constructed in accordance with the principles of the present invention; 
         FIG. 7  is a diagram of another exemplary tag having an antenna constructed in accordance with the principles of the present invention; and 
         FIG. 8  is a diagram illustrating an example of a three-dimensional power gain radiation pattern of the antenna of the tag of  FIG. 7  constructed in accordance with the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawing figures in which like reference designators refer to like elements, there is shown in  FIG. 3  a diagram of an exemplary system constructed in accordance with the principles of the present invention and designated generally as “ 300 ”. Communication system  300  provides an electronic identification system in the embodiment described herein. Further, the described communication system  300  is configured for backscatter communications as described in detail below. It is contemplated that other communication protocols can be utilized in other embodiments. 
     The depicted communication system  300  includes at least one reader  302  having at least one electronic wireless remote communication device  306 . Radio frequency (“RF”) communications can occur between a reader  302  and remote communication devices  306  for use in identification systems and product monitoring systems as exemplary applications. 
     Remote communication devices  306  include radio frequency identification (“RFID”) devices in the embodiments described herein. Multiple wireless remote communication devices  306  typically communicate with reader  302  although only one such device  306  is illustrated in  FIG. 3 . 
     Although multiple communication devices  306  can be employed in communication system  300 , there is typically no communication between the multiple communication devices  306  themselves. Instead, the multiple communication devices  306  communicate with reader  302 . Multiple communication devices  306  can be used in the same field of reader  302 , i.e., within the communication range of reader  302 . Similarly, multiple readers  302  can be in proximity to one or more of devices  306 . 
     Remote communication device  306  is configured to interface with reader  302  using a wireless medium in one embodiment. More specifically, communication between communication device  306  and reader  302  occur via an electromagnetic link, such as an RF link, e.g., at microwave frequencies in the described embodiment. Reader  302  is configured to output forward link wireless communication signals  308 . Further, reader  302  is operable to receive return link wireless communication signals  310 , e.g., a reply signal, from devices  306  responsive to the forward link communication signals  308 . In accordance with the above, forward link communication signals and return link communication signals are wireless signals, such as radio frequency signals. Other forms of communication signals, such as infrared, acoustic, and the like are contemplated. 
     Reader unit  302  includes at least one antenna  312  as well as transmitting and receiving circuitry, similar to that implemented in devices  306 . Antenna  312  comprises a transmit/receive antenna connected to reader  302 . In an alternative embodiment, reader  302  can have separate transmit and receive antennas. 
     In operation, reader  302  transmits a forward link communication signal  308 , e.g., an interrogation command signal, via antenna  312 . Communication device  306  is operable to receive the incoming forward link signal  308 . Upon receiving signal  308 , communication device  306  responds by communicating the responsive return link communication signal  310 , e.g., a responsive reply signal. Communications within system  300  are described in greater detail below. 
     In one embodiment, responsive return link communication signal  310 , e.g., a responsive reply signal is encoded with information that uniquely identifies or labels the particular device  306  that is transmitting so as to identify any object, animal, or person with which communication device  306  is associated. Communication devices  306  can be RFID tags that are attached to objects or people where each tag is programmed with information relating to the object or person to which it is attached. The information can take a wide variety of forms and can be more or less detailed depending on the needs to be served by the information. For example, the information may include merchandise identification information, such as a universal product code. A tag may include identifying information and security clearance information for an authorized person to whom the tag has been issued. A tag may also have a unique serial number, in order to uniquely identify an associated object or person. Alternatively, a tag may include more detailed information relating to an object or person, such as a complete description of the object or person. As a further exemplary alternative, a tag may store a single bit, in order to provide for theft control or simple tracking of entry and departure through the detection of an object or person at a particular reader, without necessarily specifically identifying the object or person. 
     Remote device  306  is configured to output a reply signal within reply link communication  310  responsive to receiving forward link wireless communication  308 . Reader  302  is configured to receive and recognize the reply signal within the reply link communication signal  310 , e.g., return signal. The reply signal can be utilized to identify the particular transmitting communication device  306  and may include various types of information corresponding to the communication device  306  including but not limited to stored data, configuration data or other command information. 
     An exemplary embodiment of a reader  302  is explained with reference to  FIG. 4 . In this embodiment, the reader  302  has a RF module or unit  400  and a controller module or unit  402 . The RF module  400  includes a radio signal source  404  for synthesizing radio frequency signals, e.g., an interrogating RF signal, that outputs a RF signal to transceiver  406  of the reader  302 . The interrogating RF signal from the source  404  uses a suitable frequency such as 915 MHz. When the radio signal source  404  is energized, transceiver  406  transmits the interrogating RF signal (typically after the RF signal has been modulated with an information signal) through antenna  312  to a suitable antenna  314  such as a dipole antenna at the wireless communication device  306 . 
     Modulated signals are received from communication device  306  via antenna  312  and passed to transceiver  406 . Controller module  402  of reader  302  receives the digital equivalent of the modulated signal. In one embodiment, controller module  402  produces signals in a sequence having a pattern identifying the pattern of the 1&#39;s and 0&#39;s in read only memory (“ROM”)  408  of communication device  306 . For example, the received and processed sequence may be compared in reader  302  with a desired sequence to determine whether the object being identified is being sought by reader  302  or not. 
     Continuing to refer to  FIG. 4 , one embodiment of remote communication device  306  is explained. The depicted communication device  306  includes a modulator  410  having a receiver/transmitter as described below and a data source such as ROM  408 , which provides a sequence of binary 1&#39;s and binary 0&#39;s in an individual pattern to identify the object. In this embodiment, a binary “1” in ROM  408  causes a modulator  410  to produce a first plurality of signal cycles and a binary “0” in ROM  408  causes the modulator  410  to produce a second plurality of signal cycles different from the first plurality of signals. The pluralities of signals cycles are sequentially produced by the modulator  410  to represent the pattern of binary 1&#39;s and binary 0&#39;s which identify the object are introduced to the dipole antenna  314  for transmission to antenna  312  at reader  302 . In another embodiment, the communication device  306  can have separate receive and transmit antennas. Communication device  306  may further include an optional power source (not shown) connected to modulator  410  to supply operational power to modulator  410 . 
       FIG. 5  illustrates a RFID tag  500  constructed in accordance with the principles of the present invention. In this embodiment, an antenna  502  can be disposed upon substrate  504 . Substrate  504  can be substantially rectangular in shape but also may have various other geometrical shapes to meet packaging and performance parameters. Substrate  504  can define a latitudinal axis  503  that is parallel to the proximal and distal longer edges of substrate  504  and intersects the center point of substrate  504 . Thus, latitudinal axis  503  lies along the y-axis and divides the substrate  504  into a distal half and a proximal half. Substrate  504  also can define a longitudinal axis  505  that is parallel to the left and right short edges of substrate  504  and intersects the center point of substrate  504 . Thus longitudinal axis  505  lies along the x-axis and divides the substrate  504  into a left half and a right half. Substrate  504  can comprise any type of material suitable for mounting antenna  502 , optional lead frame  512 , and RFID chip  510 . For example, material for substrate  504  may include base paper, polyethylene, polyester, and so forth. The particular material implemented for substrate  504  may impact the RF performance of RFID tag  500 . More particularly, the dielectric constant and the loss tangent may characterize the dielectric properties of an appropriate substrate material for use as substrate  504 . 
     The antenna  502  can have multiple antenna portions, such as a first antenna portion  506  and a second antenna portion  508 . The first antenna portion  506  can be connected to a first side  512 A of lead frame  512 . Second antenna portion  508  can be connected to a second side  512 B of lead frame  512 . RFID chip  510  may be connected to lead frame  512  by ultrasonically bonding lead frame  512  to the conductive pads on RFID chip  510 . As illustrated in  FIG. 5 , RFID chip  510  and lead frame  512  can be placed near the proximal longer edge of the dielectric substrate material of substrate  504 . In this embodiment, RFID chip  510  and lead frame  512  can be placed 1 to 5 mm from the proximal longer edge of the substrate  504 . The ends of lead frame  512  may be physically and electrically bonded to the antenna pattern of antenna  502 . 
     The first antenna portion  506  can have a first antenna end  506 A and a second antenna end  506 B. Similarly, second antenna portion  508  can have a first antenna end  508 A and a second antenna end  508 B. The first antenna end  506 A of first antenna portion  506  is connected to lead frame  512 A. The first antenna portion  506  can include several segments  514 A,  514 B,  514 C and  514 D to define a section of the antenna pattern of antenna  502 . The second antenna portion  508  can include several segments  516 A,  516 B and  516 C to define a second section of the antenna pattern of antenna  502 . In this embodiment, segment  514 A is disposed on substrate  504  and extends outward from RFID chip  510  toward the right short edge of substrate  504  in a substantially parallel direction to the proximal longer edge of substrate  504 . Segment  514 B is disposed on substrate  504  and extends outward from the end of segment  514 A toward the distal longer edge of substrate  504  in a substantially parallel direction to the right edge of substrate  504 . Segment  514 C is disposed on substrate  504  and extends inward from the end of segment  514 B toward the left short edge of substrate  504  in a substantially parallel direction to the distal longer edge of substrate  504 . Segment  514 D is disposed on substrate  504  and extends inward from the end of segment  514 C toward the proximal longer edge of substrate  504  in a substantially parallel direction to the left short edge of substrate  504 . 
     Continuing to refer to  FIG. 5 , segment  516 A is disposed on substrate  504  and extends outward from RFID chip  510  toward the left short edge of substrate  504  in a substantially parallel direction to the proximal longer edge of substrate  504 . Segment  516 B is disposed on substrate  504  and extends outward from the end of segment  516 A toward the distal longer edge of substrate  504  in a substantially parallel direction to the left short edge of substrate  504 . Segment  516 C is disposed on substrate  504  and extends inward from the end of segment  516 B toward the right edge of substrate  504  in a substantially parallel direction to the distal longer edge of substrate  504 . In this embodiment, segment  516 C can extent substantially the full length of the substrate  504  from the left short edge of substrate  504  to the right edge of substrate  504 . In this embodiment, the segment  516 C of second antenna portion  508  can be positioned closer to the distal longer edge of substrate  504  than the segment  514 C of the first antenna portion  506  and at least partially enclose the second end  506 B of the first antenna portion  506 . The segment  516 C can be modified by further extension and wrapping or by further reduction to achieve the appropriate resonance frequency for wireless communication. 
     The antenna pattern of  FIG. 5  advantageously generates the antenna radiation pattern  600  as illustrated in  FIG. 6 . The antenna radiation pattern  600  of tag  500  has a direction of sensitivity in an orthogonal direction, e.g., the z-axis, to the substrate  504  plane, e.g., the y-axis. A comparison of the graph of  FIG. 6  and the graph of  FIG. 2 , illustrates that the radiation pattern  600  of tag  500  is rotated approximately 90 degrees to the left about the x-axis as opposed to the radiation pattern  200  of tag  100 . In other words, the null of the radiation pattern  600  is orthogonal to the plane defined by the substrate  504 . Thus, unlike the radiation pattern  200  of conventional tag  100 , the direction of sensitivity of tag  500 , as evidenced by the null  602 , is orthogonal or normal to the tag plane. Therefore, the effects of a conductive element or surface, e.g., a metal surface or EAS tag (not shown), to which the tag  500  can be attached is minimized, since the external excitation field couples into tag  500  along the orthogonal axis normal to the plane defined by the conductive element or surface. 
       FIG. 7  illustrates an embodiment of a RFID tag  700  constructed in accordance with the principles of the present invention. In this embodiment, an antenna  702  can be disposed upon substrate  704 . Substrate  704  can be similar to substrate  504  in material and geometric shape as described above with respect to substrate  504 . Substrate  704  can define a latitudinal axis  703  that is parallel to the proximal and distal longer edges of substrate  704  and intersects the center point of substrate  704 . Thus latitudinal axis  703  lies along the y-axis and divides the substrate  504  into a distal half and a proximal half. Substrate  704  also can define a longitudinal axis  705  that is parallel to the left and right short edges of substrate  704  and intersects the center point of substrate  704 . Thus longitudinal axis  703  lies along the x-axis and divides the substrate  704  into a left half and a right half. 
     The antenna  702  can have multiple antenna portions, such as a first antenna portion  706  and a second antenna portion  708 . The first antenna portion  706  can be connected to a first side  712 A of lead frame  712 . Second antenna portion  708  can be connected to a second side  712 B of lead frame  712 . RFID chip  710  may be connected to lead frame  712  by ultrasonically bonding lead frame  712  to the conductive pads on RFID chip  710 . As illustrated in  FIG. 7 , RFID chip  710  and lead frame  712  can be placed near the proximal longer edge of the dielectric substrate material of substrate  704 . In this embodiment, RFID chip  710  and lead frame  712  can be placed 1 to 5 mm from the proximal longer edge of the substrate  704 . The ends of lead frame  712  may be physically and electrically bonded to the antenna pattern of antenna  702 . 
     The first antenna portion  706  can have a first antenna end  706 A and a second antenna end  706 B. Similarly, second antenna portion  708  has a first antenna end  708 A and a second antenna end  708 B. The first antenna end  706 A of first antenna portion  706  is connected to lead frame  712 A. The first antenna portion  706  can include several segments  714 A,  714 B,  714 C,  714 D and  714 E to define a section of the antenna pattern of antenna  702 . The second antenna portion  708  can include several segments  716 A,  716 B,  716 C,  716 D and  716 E to define a second section of the antenna pattern of antenna  702 . In this embodiment, segment  714 A is disposed on substrate  704  and extends outward from RFID chip  710  toward the right edge of substrate  704  in a substantially parallel direction to the proximal longer edge of substrate  704 . Segment  714 B is disposed on substrate  704  and extends outward from the end of segment  714 A toward the distal longer edge of substrate  704  in a substantially parallel direction to the right edge of substrate  704 . Segment  714 C is disposed on substrate  704  and extends inward from the end of segment  714 B toward the center portion of substrate  704  in a substantially parallel direction to the distal longer edge of substrate  704 . Segment  714 D is disposed on substrate  704  and extends inward from the end of segment  714 C toward the proximal longer edge of substrate  704  and segment  714 A in a substantially parallel direction to the left short edge of substrate  704 . Segment  714 E is disposed on substrate  704  and extends outward from the end of segment  714 D toward the right edge of substrate  704 . 
     Continuing to refer to  FIG. 7 , segment  716 A is disposed on substrate  704  and extends outward from RFID chip  710  toward the left short edge of substrate  704  in a substantially parallel direction to the proximal longer edge of substrate  704 . Segment  716 B is disposed on substrate  704  and extends outward from the end of segment  716 A toward the distal longer edge of substrate  704  in a substantially parallel direction to the left short edge of substrate  704 . Segment  716 C is disposed on substrate  704  and extends inward from the end of segment  716 B toward the center portion of substrate  704  in a substantially parallel direction to the distal longer edge of substrate  704 . Segment  716 D is disposed on substrate  704  and extends inward from the end of segment  716 C toward the proximal longer edge of substrate  704  and segment  716 A in a substantially parallel direction to the left short edge of substrate  704 . Segment  716 E is disposed on substrate  704  and extends outward from the end of segment  716 D toward the left short edge of substrate  704 . In this embodiment, the first antenna portion  706  and the second antenna portion  708  are substantially symmetrical. 
     The antenna pattern  702  illustrated in  FIG. 7  can be overlaid on or incorporated with a conductive element or surface  718 , e.g., an electronic article surveillance (“EAS”) tag such as the UltraMax® manufactured by Sensormatic Electronics Corporation, to form RFID tag  700 , which advantageously generates the antenna radiation pattern  800  as illustrated in  FIG. 8 . In this embodiment, the electronic article surveillance device can be, for example, a magneto-acoustic device. The antenna radiation pattern  800  of antenna pattern  702  overlaid on the conductive element or surface  718  has a direction of sensitivity in an orthogonal direction, e.g., the z-axis, to the substrate  704  plane, e.g., the y-axis. The field effects of the symmetrical geometry of the first antenna portion  706  and the second antenna portion  708  combined with the RFID chip  710  and optional lead frame  712  positioned near the proximal longer edge of substrate  704  generate a radiation pattern with a maximum gain that is coplanar with the tag. A comparison of the graph of  FIG. 8  and the graph of  FIG. 6 , illustrates similar rotational orientation and field strength for the radiation patterns of tag  800  and tag  600 . 
     A comparison of the graph of  FIG. 8  and the graph of  FIG. 2 , illustrates that the radiation pattern  800  of tag  700  is rotated approximately 90 degrees to the left about the x-axis as opposed to the radiation pattern  200  of tag  100 . In other words, the null of the radiation pattern  800  is orthogonal to the plane defined by the substrate  704 . Thus, unlike the radiation pattern  200  of conventional tag  100 , the direction of sensitivity of tag  700 , as evidenced by the null  802 , is orthogonal or normal to the tag plane and the plane of the conductive element or surface  718 . Therefore, the effects of a conductive element or surface, e.g., a metal surface or EAS tag, to which the tag antenna  702  can be combined, are used to generate the desired radiation pattern  800  with a maximum gain that is coplanar with the tag. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.