Abstract:
Methods, systems, and apparatuses for automated manufacturing microstrip element antennas is described. The microstrip element antenna comprises a printed circuit layer, a dielectric layer and a ground plane layer. Mass manufacturing process for such microstrip element antennas without any substantial manual assembly process is described. Automation of the manufacturing steps leads to lower production costs, faster production and a higher yield.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to radio frequency identification (RFID) technology, and in particular, to improved manufacturing process for microstrip element antenna used in RFID tags. 
   2. Background Art 
   Radio frequency identification (RFID) tags are electronic devices that may be affixed to items whose presence is to be detected and/or monitored. Some RFID tags include microstrip element antennas, also known as patch antennas to transmit and receive information. Microstrip element antennas are mass produced multilayered devices requiring a complicated assembly process. Present assembly techniques for microstrip antennas require a considerable degree of manual assembly thereby increasing the cost of the final product and the production time required for manufacturing an individual microstrip antenna. Because of this complicated assembly process, it is not cost effective to use microstrip antennas for high volume tag applications. 
   Thus, what is needed are ways to improve and automate manufacturing process for microstrip antenna to reduce the production time and cost. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
     The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
       FIG. 1  illustrates an exemplary environment in which RFID readers communicate with an exemplary population of RFID tags. 
       FIG. 2  illustrates a microstrip element antenna, according to an embodiment of the present invention. 
       FIG. 3  illustrates a cross-section of a microstrip element antenna showing further details. 
       FIG. 4  illustrates an exemplary assembly process for manufacture of a microstrip element antenna, according to another embodiment of the present invention. 
       FIG. 5  illustrates a flowchart showing a process for automated mass production of microstrip element antenna. 
   

   The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Introduction 
   Methods, systems, and apparatuses for RFID devices are described herein. In particular, methods, systems, and apparatuses for improved automated manufacturing of microstrip element antennas are described. 
   The present specification discloses one or more embodiments that incorporate the features of the invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the claims appended hereto. 
   References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
   Furthermore, it should be understood that spatial descriptions (e.g., “above,” “below,” “up,” “left,” “right,” “down,” “top,” “bottom,” “vertical,” “horizontal,” etc.) used herein are for purposes of illustration only, and that practical implementations of the structures described herein can be spatially arranged in any orientation or manner. Likewise, particular bit values of “0” or “1” (and representative voltage values) are used in illustrative examples provided herein to represent data for purposes of illustration only. Data described herein can be represented by either bit value (and by alternative voltage values), and embodiments described herein can be configured to operate on either bit value (and any representative voltage value), as would be understood by persons skilled in the relevant art(s). 
   Example RFID System 
   Before describing embodiments of the present invention in detail, it is helpful to describe an example RFID communications environment in which the invention may be implemented.  FIG. 1  illustrates an environment  100  where RFID tag readers  104  communicate with an exemplary population  120  of RFID tags  102 . As shown in  FIG. 1 , the population  120  of tags includes seven tags  102   a - 102   g . A population  120  may include any number of tags  102 . One or more tags  102  may include, among other elements, a microstrip element antenna. 
   Environment  100  includes one or more readers  104 . For example, environment  100  includes a first reader  104   a  and a second reader  104   b . Readers  104   a  and/or  104   b  may be requested by an external application to address the population of tags  120 . Alternatively, reader  104   a  and/or reader  104   b  may have internal logic that initiates communication, or may have a trigger mechanism that an operator of a reader  104  uses to initiate communication. Readers  104   a  and  104   b  may also communicate with each other in a reader network. 
   As shown in  FIG. 1 , reader  104   a  transmits an interrogation signal  110  having a carrier frequency to the population of tags  120 . Reader  104   b  transmits an interrogation signal  110   b  having a carrier frequency to the population of tags  120 . Readers  104   a  and  104   b  typically operate in one or more of the frequency bands allotted for this type of RF communication. For example, frequency bands of 902-928 MHz and 2400-2483.5 MHz have been defined for certain RFID applications by the Federal Communication Commission (FCC). 
   Various types of tags  102  may be present in tag population  120  that transmit one or more response signals  112  to an interrogating reader  104 , including by alternatively reflecting and absorbing portions of signal  110  according to a time-based pattern or frequency. This technique for alternatively absorbing and reflecting signal  110  is referred to herein as backscatter modulation. Readers  104   a  and  104   b  receive and obtain data from response signals  112 , such as an identification number of the responding tag  102 . In the embodiments described herein, a reader may be capable of communicating with tags  102  according to any suitable communication protocol, including but not limited to Class 0, Class 1, EPC Gen 2, other binary traversal protocols, or slotted aloha protocols. 
   Example Implementation 
     FIG. 2  shows an example of a low cost light-weight single microstrip element antenna  200 . Such a microstrip element antenna  200  can be used, for example as the antenna for a tag  102  and/or reader  104 , in an environment described by  FIG. 1 , as above. Microstrip element antenna  200  is also known as a patch antenna, as is well known to those skilled in the art. As shown in  FIG. 2 , microstrip element antenna  200  comprises various layers including a radiator layer  202 , a foam core layer  206 , and a ground plane layer  208 . In an embodiment, radiator layer  202  may have graphics printed thereon. Printed graphics  204  can be a hologram, an identification label or a decorative graphic, depending on specific applications where microstrip element antenna  200  may be used. 
   Radiator layer  202  can be made of plastic or other flexible materials, well known to those skilled in the art. Radiator layer  202  can further include additional electrical components, resonating elements, circuit traces, and the like. Such electronics components, circuit traces or resonating elements can be placed on the radiator layer  202  by various fabrication techniques, such as thin-film technology. 
   Foam core  206  can be any dielectric material, for example and not by way of limitation, organic compounds, alloys or plastic. Ground plane layer  208  serves as a ground plane for the components of printed circuit layer  202 . Ground plane layer  208  can be made of, for example and not by way of limitation, any standard metal like copper or a suitable alloy. 
   Microstrip element antenna  200  is described in further detail in  FIG. 3 .  FIG. 3  shows a cross-section  300  of microstrip element antenna  200 , according to embodiments of present invention.  FIG. 3  illustrates a microstrip antenna as a top section  310  and a lower section  320  for ease of description. During the manufacturing process, top section  310  is coupled to lower section  320 . In addition to the elements mentioned immediately above, cross-section  300  of microstrip element antenna  200  further shows a self-adhesive layer  302  coupled to radiator layer  202 . Optionally, radiator layer  202  and/or printed graphics  204  can be covered by a plastic film  322 . 
   In an embodiment, ground plane layer  208  may have self adhesive layer for coupling to foam core layer  206 . Foam core layer  206  may have a component recess for electronic component  338 , conductive traces and/or resonating element  336  residing on radiator layer  202 . The component recess allows for the microstrip antenna to maintain a substantially flat top and bottom surface after assembly. Dimensions of cross-section  300  and therefore, microstrip element antenna  200  can be adjusted and pre-programmed per specific applications. 
   As illustrated in  FIG. 3 , a backing layer  304  may be coupled to a top surface of adhesive layer  302 . Backing layer  304  is removed from lower section  320  to expose adhesive layer  302 . After assembly, foam core layer  206  is coupled to radiator layer  202  via adhesive layer  302 . 
     FIG. 4  illustrates an exemplary assembly system  400  for manufacture of microstrip element antenna  200 , according to one embodiment of the present invention. System  400  receives a roll having a series of lower sections  320  connected in a strip or web (referred to herein as “lower layer strip”). The roll of lower sections  320  is placed on roller  408  such that backing layer  302  is the outermost layer. System  400  also receives a roll having a ground plane strip. 
   As shown in  FIG. 3 , ground plane  208  is a self-adhesive ground plane. Accordingly, a backing layer  432  is coupled to the adhesive surface of ground plane  208  to form the ground plane strip. The roll of ground plane strip is placed on roller  418  such that backing layer  432  is the outermost layer. 
   A foam core strip  404  (also referred to as an extruded foam core strip  404 ) is moved linearly through system  400  at a pre-determined but adjustable velocity. Foam core strip  404  has a first and a second opposing surface. 
   The lower layer strip is moved through system  400  by unrolling lower layer strip from roller  408  at a pre-determined velocity. As lower layer strip  406  is unrolled, backing layer  432   a  is removed (or peeled) from the lower layer strip  406  by roller drum  436   a  and roller drum  402   a . The peeled backing layer  432   a  is deposited on roller drum  402   a . Roller  408  can be rotated at an adjustable angular velocity. Lower layer strip  406  is rolled out to pinch guide roller  410   a  such that the lower layer strip is drawn between the guide roller  410   a  and the first surface of the foam core strip. Pinch guide roller  410   a  is also rotating at an adjustable angular velocity and acts as a guiding mechanism to attach the lower layer strip  406  to the a first surface of foam core strip  404 . 
   In a similar fashion, the ground plane strip is moved through the system by unrolling the ground plane layer from roller  418 . As the ground plane strip is unrolled, backing layer  432   b  is removed (or peeled) from the ground strip by roller drum  436   b  and roller  402   b . The peeled backing layer  432   a  is deposited on a roller drum  402   b . Roller  418  can be rotated at an adjustable angular velocity. Ground plane strip  420  is rolled out to pinch guide roller  410   b  such that the ground plane strip is drawn between pinch guide roller  410   b  and the second surface of the foam core strip. Pinch guide roller  410   b  is also rotating at an adjustable angular velocity and acts as a guiding mechanism to attach ground plane strip  420  to the second surface of foam core strip  404 . 
   First roller  410   a  applies a force to lower section strip  406  causing the adhesive layer to couple to the first surface of foam core strip  404 . At substantially the same time, roller  410   b  applies a force to ground plane strip  420  causing the adhesive to couple to the second surface of foam core strip  404 . 
   After lower section strip  406  and ground plane strip  420  have been coupled to foam core strip  404 , a multi-layered strip  422  is formed on the linearly moving assembly line. Multi-layered strip  422  is then moved to a cutter  414 . Cutter  414  can cut multi-layered strip  422  into a plurality of separate microstrip element antennas, similar to microstrip element antenna  200 . The size of the resulting microstrip element antennas can be adjusted depending on specific application in which microstrip element antenna is to be used in. Further, cutter  414  can be a mechanical cutting device, a heat cutter, a laser cutting tool, or any other cutting mechanism well known to one skilled in the art. In an embodiment, the motion of cutter  414  as shown by arrow  424 , can be adjusted for different speeds of assembly thereby varying the production yield according to a specific need of the application or the environment in which microstrip element antenna  200  is to be used in. In an embodiment, cutter  414  is moving in a direction relatively perpendicular to the linear motion of foam core strip  404 , as shown by an arrow  424  on cutter  414 . 
     FIG. 5  illustrates a flowchart  500  of an exemplary assembly process that can be used to manufacture microstrip element antenna  200 , according to various embodiments of the present invention. Flowchart  500  is described with continued reference to antenna  200  and system  400 . However, flowchart  500  is not limited to those embodiments. Note that the steps in the flowchart  500  do not necessarily have to be in the order shown. 
   In step  502   a , a roll having a self-adhesive ground plane strip is placed on feed roller  418 . Similarly, in step  502   b , a roll having a strip of lower sections is placed on a feed roll  408 . 
   In step  503   a , ground plane strip is unrolled and backing  432  is peeled off. Ground plane roll is also drawn between pinch guide roller  410   b  and the second surface of the foam core strip. 
   Similarly, in step  503   b , the lower section strip is unrolled and backing  432  is peeled off (or removed). Lower section strip is also drawn between pinch guide roller  410   a  and the first surface of foam core strip  404 . 
   In step  506 , ground plane strip  420  is attached to a first surface of foam core strip  404 . Roller  410   b  applies a force to cause a surface of foam core strip  404  and ground plane strip  420  to adhere. At the same time, lower section strip is attached to the opposing surface of foam core strip  404  using roller  410   a . As lower section moves under roller  410   a , roller  410   a  asserts a force on lower section strip causing the strip to adhere to the first surface of foam core strip  404 . 
   The angular velocity of rollers is adjustable such that it substantially matches with the linear velocity of foam core strip  404 , Throughout the steps  502 - 506 , foam core strip  404  is moving linearly in a fixed direction at a fixed velocity. However, as can be easily contemplated by those skilled in the art, the direction and velocity of motion of various elements of the present invention can be adjusted by programming, or other techniques. 
   Step  508  is optional. In step  508 , graphics may be printed on an exposed surface of lower section strip  406 . Alternatively, graphics may be printed on lower section strip prior to the assembly process  500 . 
   In step  510 , individual multi-layered microstrip antenna element  200  are formed by cutting through the assembled strip. The cutting techniques and cutting dimensions may vary as per the need of the application in which microstrip element antenna  200  may be used, as is well known to those skilled in the art. 
   Alternative embodiments of the microstrip element antenna  200  can be contemplated by those skilled in the art after reading this disclosure. Further, microstrip element antenna  200  may be used in conjunction with any type of reader antenna known to persons skilled in the relevant art(s), including a vertical, dipole, loop, Yagi-Uda, or slot antenna type. For description of an example antenna suitable for reader  104 , refer to U.S. Ser. No. 11/265,143, filed Nov. 3, 2005, titled “Low Return Loss Rugged RFID Antenna,” now pending, which is incorporated by reference herein in its entirety. 
   The methods and systems described herein maybe applicable to a manufacturing process of any type of microstrip element antenna  200 , for example a patch antenna. Microstrip element antenna  200  can further include a substrate and an integrated circuit (IC). Further, microstrip element antenna  200  may include any number of one, two, or more separate antennas and thus, can be a part of an antenna array. Further still, in an array configuration, microstrip element antenna  200  can be implemented as any suitable antenna type, including dipole, loop, slot, or patch antenna type. 
   Conclusion 
   While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.