Patent Abstract:
The present invention provides an automated system for asset tracking and management and utilizes near field Radio Frequency IDentification (RFID) technology. RFID tags are attached to the assets, and RFID antennas (and corresponding readers) are strategically located in close proximity to read the tags. As applied to a rack or cabinet, near-field antennas are mounted along one of the mounting posts at each rack unit location such that when a piece of equipment (rack mounted or rail mounted) is installed at a particular rack unit space, the tag will be read and registered in an RFID management system. A magnetic field shaping arrangement ensures that crosstalk between adjacent rack positions is prevented. Ferrite elements are used to control the magnetic field.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/394,924, filed Oct. 20, 2010, the subject matter of which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND  
       [0002]    This invention relates generally to asset tracking systems, and more particularly to Radio Frequency IDentification (RFID) systems that employ ferrite material to shape the magnetic field pattern of an antenna-like source or detector 
         [0003]    Asset tracking within Data Centers is important for the assistance in inventory audits, physical location identification of assets that require repair or de-commissioning, and for rack environmental management. The industry currently addresses this problem largely by the implementation of manual techniques (handwritten or Excel® spreadsheet-based physical location of assets). Some data center managers have improved upon these techniques by incorporating barcode systems into their asset tracking methods. Nevertheless, the bar code methods are manually implemented, and therefore have cost and accuracy issues, notwithstanding that they are certainly better than processes that are completely manual. 
         [0004]    There is, therefore, a need in the IT data center market for a system that tracks assets automatically. There are a number of solutions that are emerging to satisfy this particular need (e.g., solutions that rely on wireless, GPS, image processing, and/or far field RFID). Another method or technology for automatic asset tracking utilizes near field RFID technology and can resolve where a particular asset is located down to the rack unit level within a rack or cabinet. 
         [0005]    RFID technology offers the following benefits over manual techniques: 1) an automated method of asset tracking and reporting; 2) a lower life cycle cost; 3) numerous different types of rack IT assets that can be tracked (e.g., patch panels, blanking panels, absence of equipment); 4) greater accuracy for asset rack unit location with accurate asset attributes; and 5) automated monitoring of rack inventory for accurate environmental management Important attributes for near-field RFID methods to gain wide acceptance in the market place are low cost and simple installation (in existing and new data centers). 
       SUMMARY. 
       [0006]    In one aspect, there is provided an automated system that, when employed for asset tracking and management, utilizes near field Radio Frequency IDentification (RFID) technology. In accordance with this aspect of the invention, RFID tags are attached to assets, and RFID antennas (and corresponding readers) are strategically located in close proximity to read the tags. To apply an RFID system to a rack or cabinet, near-field antennas are mounted along one of the mounting posts at each rack unit location such that when a piece of equipment (rack mounted or rail mounted) is installed at a particular rack unit space, the tag will be read and registered in an RFID management system. 
         [0007]    In one aspect of the invention, there is provided a method of tracking equipment installed on a rack. The method includes attaching an RFID tag to a mounting portion of the equipment; attaching an antenna system to the rack, the antenna system issuing a magnetic field that impinges upon the RFID tag; and shaping the magnetic field issued by the antenna system in response to a distance between the antenna system and the RFID tag. 
         [0008]    In one embodiment of this aspect, the step of attaching an antenna system to the rack is performed on a mounting post of the rack. In one embodiment of this aspect, the step of attaching an RFID tag is performed on a mounting ear of the equipment in close proximity of the mounting post of the rack. 
         [0009]    In one aspect of the invention, there is provided a method of manufacturing a RFID tag. The method includes attaching a RFID integrated circuit to a first printed circuit board and bonding the first printed circuit board to a substrate. In one embodiment of this aspect, the first printed circuit board is a flex printed circuit board, whereby an RFID strap is formed. In some embodiments, prior to performing the step of bonding the first printed circuit board to a substrate there are provided the further steps of adhering the flex printed circuit board to an antenna flex printed circuit board, to form an inlay and adhering the inlay to a substrate. 
         [0010]    In one aspect of the invention, there is provided a system for protecting equipment that is to be installed on a rack. The system includes a near field RFID tag installed in a mounting portion of the equipment that is to be protected. There is additionally provided an antenna array installed on the rack in predetermined relation to the near field RFID tag for issuing a magnetic field. In one embodiment of this aspect, there is further provided a magnetic field shaping arrangement for controlling the magnetic field issued by the antenna array. The magnetic field shaping arrangement includes, in some embodiments, a ferrite element installed on the near field RFID tag. In one embodiment, the magnetic field shaping arrangement is provided with a ferrite member installed in the vicinity of the antenna array distal from the near field RFID tag. 
         [0011]    The scope of the present invention is defined solely by the appended claims and is not affected by the statements within this summary. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0013]      FIGS. 1   a  to  1   d  depict simplified isometric and plan representations of a specific illustrative embodiment of the invention; 
           [0014]      FIGS. 2   a  to  2   c  depict simplified schematic and isometric representations that are useful in describing a near field magnetic coupling technique that is used to communicate between an antenna array and an IT equipment tag, in accordance with the invention; 
           [0015]      FIGS. 3   a  to  3   d  depict plan and side view simplified representations useful to describe a construction that utilizes ferrite material for magnetic field shaping of an antenna array module and an IT equipment tag for a rack-unit-based near field RFID system, in accordance with the invention; 
           [0016]      FIGS. 4   a  to  4   d  depict simplified schematic representations of magnet field lines between an antenna array and an IT equipment tag for the embodiments with and without a ferrite material within the IT equipment tag; 
           [0017]      FIGS. 5   a  to  5   c  depict graphical and simplified isometric representations that are useful to illustrate the RFID system sensitivity as a function of physical proximity between a printed circuit board (PCB) antenna and the IT equipment tag; 
           [0018]      FIG. 6  depicts a simplified schematic representation of the shape of the near field magnetic field pattern; 
           [0019]      FIG. 7  depicts a simplified representation that is useful to illustrate the components of a specific illustrative embodiment of the invention of far field IT equipment RFID tags, as well as an illustrative manufacturing technique; 
           [0020]      FIGS. 8   a  and  8   b  depict an IT equipment tag that consists of two sections, and the optimization of the circuit to achieve maximum power transfer from the source into the IC load; 
           [0021]      FIGS. 9   a  and  9   b  depict a specific illustrative embodiment of a tag in which the reactance of an antenna and the input impedance of an RFID IC cancel one other; 
           [0022]      FIGS. 10   a  to  10   d  depict a specific illustrative embodiment of an IT equipment RFID tag in which ferrite is used to enhance received coupled power; 
           [0023]      FIGS. 11   a  and  11   b  depict structural representations of a further specific illustrative embodiment of an IT equipment RFID tag that employs ferrite to enhance the received coupled power; and 
           [0024]      FIGS. 12   a  and  12   b  depict yet another illustrative embodiment of an IT equipment RFID tag that employs ferrite to enhance the received coupled power. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    With reference to  FIGS. 1   a  to  1   d,  simplified isometric and plan representations of a specific illustrative embodiment of the invention are depicted along with an illustrative asset tracking system.  FIG. 1   a  illustrates the use of RFID at the rack unit level of granularity. More specifically, RFID tagged equipment is illustrated in use with a rack unit  110 . 
         [0026]    The technique of the present invention relies on near field magnetic coupling between an antenna array  112  mounted on the rack&#39;s mounting post  114  and an RFID tag  120  that is installed on RFID tagged equipment  130 . Referring to  FIG. 1   b,  there is shown in isometric representation RFID tag  120  that is attached to IT equipment  130  that mounts in the rack.  FIGS. 1   a  through  1   d  illustrate two key components of the RFID rack-unit-based asset tracking management system of the present invention, specifically antenna array  112  and RFID tag  120  attached to the IT equipment. Antenna array  112 , which as stated is mounted onto the rack&#39;s mounting post  114 , contains one near field coupling antenna  132  (or sensor) per rack unit space. The IT equipment tags are mounted as shown on the IT equipment assets that are to be tracked. These tags can be placed on equipment that is mounted on a rail  140 , as shown in  FIG. 1   b,  or mounted on a post  150 , as shown in  FIG. 1   c.  Since the IT equipment RFID tags are typically mounted on metallic surfaces, such as surface  155  shown in  FIG. 1   d,  the performance of a tag directly on a metallic surface will be poor unless special design considerations are applied. 
         [0027]    Referring again to  FIGS. 1   a  to  1   d,  when an equipment asset is mounted onto the rack, the previously provisioned RFID tag mounted on equipment mounting ear  160  is interrogated by a reader (not shown in this figure) via post mounted antenna array  112 . The reader reports that a piece of equipment has been inserted into a particular rack at a particular rack unit level to an asset tracking management software. Conversely, when the equipment is removed from the rack, the reader also notifies the asset tracking management software (not shown). RFID tags  120  are, in some embodiments, located on the equipment&#39;s mounting ears  160  as shown in  FIG. 1   a  through  FIG. 1   d . As indicated above, these equipment tags communicate to an RFID reader via the post-mounted antennas. 
         [0028]    Through the application of this RFID technology, assets within a data center (not shown) can be effectively and automatically tracked and managed. The RFID tags can be mounted on both active and passive equipment that is either front-post-mounted or rail-mounted. The RFID antennas can be mounted at each rack unit location in close proximity to the tagged equipment. This technique allows automatic detection of any tagged equipment that is mounted within the rack. Software can then be utilized to provide a complete and visible configuration of the rack. (Sub-equipment assets like line cards and blade servers are detectable using extensions of the present RFID system. Alternatively, such sub-equipment assets are detectable with the use of equipment chassis network interfaces, such as Integrated Product Lifecycle Management (IPLM) systems. 
         [0029]    The RFID tags discussed above for automatic rack unit detection utilize near-field coupling to establish the detection and communication between a reader and an equipment tag. The definition of electromagnetic near-field and far-field modes of operation is generally related to the distance between the source antenna and the measuring point or region. The near field region is typically within a radius much less than its wavelength r  21  &lt;λ, while the far field region is typically outside a radius much greater than its wavelength r&gt;&gt;λ. Since the most common RFID high-frequency signal transmits at about 900 MHz in free space, the wavelength is about 33.3 cm (13.1 in). For this frequency range, the regions are defined as follows: Near Field, r&lt;1-2 in. and far field, r&gt;5-10 ft. It is to be noted that it is a misnomer to use the phrase “near-field antenna,” as this falsely implies that an electromagnetic wave is launched. In reality, this mechanism is preferably described as a magnetic coupling method. 
         [0030]    Characterization of the magnetic field shape that the antenna emits and the preferred magnetic field shapes that the tag is optimized to are important to the overall performance of the system. 
         [0031]      FIG. 2  is useful to depict the near field magnetic coupling technique that is used in the practice of the invention to communicate between the antenna array and the IT equipment tag. Elements of structure that have previously been discussed are similarly designated. As shown in  FIG. 2   a , magnetic field  210  is generated by a current (not shown) on a trace  215  on PCB  220  of antenna array  112  that couples with the IT equipment tag&#39;s antenna. It is to be noted that the shape of the magnetic field pattern is dependent upon various parameters, illustratively including the dimensions and permeability of a ferrite  225  that is placed behind the current-carrying trace. The length, width, and height of the current carrying trace  215  on the PCB, and any metallic surfaces behind the ferrite, such as metal enclosure  230 , or on the PCB in front of the current carrying trace, will influence the shape and intensity of the magnetic field. 
         [0032]    The antenna formed by the current carrying trace on the PCB is implemented as shown in  FIG. 2   b . As shown in  FIG. 2   b , trace  215  is juxtaposed to ferrite  225  and connected to a PCB transmission line  235 . A ground plane  240  is schematically represented in  FIG. 2   b.    
         [0033]    An electrical equivalent model of this antenna is shown in  FIG. 2   c . It is important in the practice of the invention that the antennas within the antenna array communicate robustly with their associated rack unit IT equipment tags and not with neighboring rack unit IT equipment tags. Hence the shape of the magnetic field generated by each antenna must be properly designed. It is seen from this figure that the equivalent circuit consists of an inductance L and a capacitance C arranged in series with one another and with an impedance matching element  245 . These electrical parameters are represented in  FIG. 2   b.    
         [0034]      FIGS. 3 and 4  illustrate the proposed construction that employs the use of ferrite material to enhance the coupling between the PCB antenna array and the IT equipment tag.  FIGS. 3   a  to  3   d  also depict schematically an IT equipment tag  120  for a rack-unit-based near field RFID system, constructed in accordance with the invention. 
         [0035]    More specifically,  FIGS. 3   a  to  3   d  are plan and side view simplified representations useful to describe a construction that utilizes ferrite material  225  for magnetic field shaping of an antenna array module  112 . Elements of structure that have previously been discussed are similarly designated. More specifically,  FIGS. 3   a  to  3   d  depict a preferred illustrative construction that utilizes ferrite material  225  for magnetic field shaping of an antenna array module  112  and an IT equipment RFID tag  120  for a rack unit based near field RFID system. The antenna array module construction&#39;s top view is depicted in  FIG. 3   a  and the side view is depicted in  FIG. 3   b.    
         [0036]      FIG. 3   a  depicts plural circuit traces  215  which are coupled by respectively associated switches S to a bus  310  that is provided with a coupler  315  that is coupled to receive and transmit RF energy to an RF source (not shown). 
         [0037]    The top view of the structure of IT equipment RFID tag  120  is depicted in  FIG. 3   c , and the side view is depicted in  FIG. 3   d . In both figures, a metal surface  320  is disposed in close proximity to traces  215  that form antenna array  112 . As depicted in  FIG. 3   c , copper trace  215  on PCB  220  is coupled to an integrated circuit  325 . In  FIG. 3   d , RFID tag  120  is separated from metal surface  320  by a ferrite spacer  327  and a filler spacer  330 . 
         [0038]      FIGS. 4   a  to  4   d  depict simplified schematic representations of magnet field lines  210  between an antenna array and an IT equipment tag for the embodiments with and without a ferrite spacer  327  within the IT equipment tag. Elements of structure that have previously been discussed are similarly designated. The embodiment of  FIG. 4   a  illustrates RFID tag  120  separated from metallic surface  320  by an air spacer  410 . Ferrite spacer  327  underneath RFID tag  120  helps to increase the received coupled power from the antenna array by “channeling” or “guiding” the magnetic field away from metallic surface  320 . Thus, it is seen in the air spacer embodiment of  FIG. 4   a  that magnet field lines  210  extend into metal surface  320 . 
         [0039]    The magnetic characteristics of the embodiment depicted in  FIG. 4   a  are depicted in  FIG. 4   b . More specifically, such magnetic characteristics are directed to the metallic material  320 . The magnetic characteristics of the embodiment depicted in  FIG. 4   c  are depicted in  FIG. 4   d , and are directed to the magnetic characteristics of the ferrite spacer  327 . 
         [0040]      FIGS. 5   a  to  5   c  depict graphical and simplified isometric representations that are useful to illustrate the RFID system sensitivity as a function of physical proximity between antenna array  112  and the IT equipment RFID tag  120 . Elements of structure that have previously been discussed are similarly designated. The sensitivity of the system is plotted in the graphical representation of  FIG. 5   a . When IT equipment RFID tag  120  is placed within the area outlined in the RFID system sensitivity graph of  FIG. 5   a , the system will operate correctly. If the tag is placed outside of this region, the tag may not operate satisfactorily. The iso-curves depicted in  FIG. 5   a  are dependent on the tags&#39; physical proximity to the antenna source as well as the overall construction of the system (e.g., the size of the ferrite core material, magnitude of transmit power from the system reader, and the shape and position of the PCB trace that forms the antenna). 
         [0041]      FIG. 6  depicts a simplified schematic representation of the shape of the near field magnetic field pattern that is useful to summarize the preferred operating distances for optimal system performance. It is to be noted that the magnetic field shape is designed to provide tolerance to the actual position of the IT equipment RFID tag  120  while minimizing any crosstalk between rack unit positions. The magnetic field lines associated with respective RFID tag  120  are represented in the figure by the plural X in a circle  620 . Outline  610  illustrates the safe operating region associated with RFID tag  120 . This outline incorporates degrees of freedom corresponding to: PCB trace length, width, and position; ferrite core length, width, and position; proximity to metal behind the ferrite; proximity to metal in front of the PCB trace; and magnitude of the transmission power level. 
         [0042]      FIG. 7  depicts a far field IT equipment RFID tag  710  and an illustrative manufacturing technique, according to one aspect of the invention. The depicted technique uses an RFID IC  720  soldered onto a Flex PCB assembly  725  that is designated an “RFID strap.” The RFID strap is, in some embodiments, glued with electrically conductive adhesive (not shown) onto another flex PCB  730 , that is termed the “antenna flex PCB.” It is to be noted that an RFID IC can be soldered directly onto the antenna flex PCB, thereby obviating the need for the herein-disclosed strap process when using appropriate manufacturing process technologies. Antenna flex PCB  730  implements either a far field antenna as shown in the figure, or a near field antenna (not shown) depending upon the design of the antenna itself. The constructed assembly is termed an “inlay,” represented by inlay  750 . An RFID tag is formed when inlay  750  is bonded onto a substrate (not specifically designated). The inlay constitutes a key component of the RFID tag of the present invention. The manufacturing process steps are illustrated by the function bocks in this figure. Systems  755  and  757  are illustrative of products that are manufactured in accordance with the disclosed manufacturing process. 
         [0043]      FIGS. 8   a  and  8   b  depict an IT equipment RFID tag  820  that consists of two sections, and the optimization of the circuit to achieve maximum power transfer from the source into the IC load. Referring to  FIG. 8   a , the IT equipment tag consists of two sections and hence is modeled in two sections, specifically a near field antenna  830  and an IC  840 . Near field antenna  830  is modeled as an ideal receiver voltage source  832  with a source resistance  834  and the reactance component  836  of the antenna itself. The IC has a complex input impedance  842  that can be represented as a reactance and a resistance  844  that represents the load of the IC. In  FIG. 8   b , when the IT equipment tag&#39;s complex antenna impedance is matched to the complex input impedance of the IC, an optimized circuit is achieved (i.e., maximum power transfer from the source into the IC load occurs when X ANT  and X IC  are conjugates of each other and hence cancel). For example, if X ANT =jωL and X IC =1/jωC (=−jωC), then when L=1/C a cancellation will occur and the circuit will have been reduced to a simple voltage divider, as depicted in  FIG. 8   b.    
         [0044]      FIGS. 9   a  and  9   b  depict an illustrative embodiment of a tag wherein the reactance impedance components of the antenna and the input of the RFID IC cancel each other. Elements of structure that have previously been discussed are similarly designated. As depicted in  FIG. 9   a , the impedance arising from the combination of resistance  934  inductance  936  from the tag&#39;s loop antenna is designed to match (i.e., provide a complex conjugate) the RFID IC&#39;s input impedance, which is the serial combination of equivalence capacitance  942  and resistance  944 , at an illustrative operating frequency of 900 MHz. As depicted in  FIG. 9   b , the impedance of the tag&#39;s loop antenna is influenced by the environment to which it is attached (not shown). In this figure, RFID tag  120  is installed on mounting ear  160  in the vicinity of a metallic surface  960 . In the embodiment, mutual coupling M is essentially the result of mutual inductance. The components designated generally as  965  represent parasitic capacitance and inductance. 
         [0045]      FIGS. 10   a  to  10   d  depict a specific illustrative embodiment of an IT equipment RFID tag  1010  in which ferrite is used to enhance received coupled power. A ferrite spacer  1015  is used under trace  1020  as shown in  FIG. 10   a  to enhance the coupled power received by RFID tag  1010 . As shown, RFID tag  1010  is installed on mounting ear  160  of the IT equipment (not shown in this figure), which is itself installed on mounting post  114 . 
         [0046]    The tag antenna is formed by a PCB trace  1050  that connects to a tag IC  1055  as shown in  FIG. 10   b . The PCB is attached (e.g., adhesive) to a plastic molded component as shown in  FIG. 10   d . A metallic rivet assembly having rivet portions  1030  and  1032 , as shown in  FIG. 10   c , is inserted onto PCB-molded component assembly, which in this embodiment includes a PCB element  1040  and a molded plastic spacer element  1045 . As shown, plastic spacer element  1045  in this specific illustrative embodiment of the invention is provided with a cavity  1047  that accommodates tag IC  1055 . 
         [0047]    The rivet assembly has two functions; first it allows the force from a screw  1060  to transfer to metallic IT equipment mounting ear  160  and mounting post  114 , and secondly it provides an electrical path from the threaded holes in the mounting ear formed by the screw to connect to the metallic post. The function of this molded component is to capture the ferrite material, protect the RFID tag, and provide a robust way for a screw to be inserted through the module as shown in  FIG. 10   c.    
         [0048]      FIGS. 11   a  and  11   b  depict structural representations of a further specific illustrative embodiment of an IT equipment RFID tag that employs ferrite  1110  to enhance the received coupled power. Ferrite  1110  is, as previously discussed, employed in the structure shown in  FIG. 11   a  to enhance the received coupled power. The ferrite is held in place by the two outer PCBs  1120  and  1122  and metallic molded component  1130 . The metallic molded component has features incorporated in to protect the RFID tag and has a raised (proud) feature  1135  that will have functionality similar to that of the rivet assembly depicted in  FIG. 10 . In this specific illustrative embodiment of the invention, feature  1135  has a height above the surface of approximately 10 mil. 
         [0049]      FIGS. 12   a  and  12   b  depict yet another illustrative embodiment an IT equipment RFID tag that employs ferrite to enhance the received coupled power.  FIG. 12   a  depicts mounting posts  1210  and  1212  that support IT equipment  1215 . A ferrite  1220  serves to enhance the received coupled power. The ferrite is held in place onto PCB  1225 , which in this embodiment is a single-sided PCB, by adhesive (not shown) or a mechanical clip (not shown). A metallic washer  1230  is attached to the bottom of solder-coated PCB pad  1232  and functions in a manner analogous to that of the rivet assembly depicted in  FIG. 10 . Also in the embodiment of  FIG. 12   a , there is depicted a tag IC  1240  that is adjoined in this specific illustrative embodiment of the invention to a foam double sided tape  1245 . 
         [0050]      FIG. 12   b  depicts a RFID tag  1250  installed on mounting ear  1255  of the IT equipment. An antenna array  1260  also is mounted in mounting post  1210 . This figure additionally depicts a cross-sectional view, and an alternative cross-sectional view taken along section A-A. 
         [0051]    The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter. 
         [0052]    While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.

Technology Classification (CPC): 6