Abstract:
The present invention relates to a SiP having reduced influence between a conductor and an antenna, and a method of designing the SiP. The SiP includes an antenna configured to function to transmit or receive data and mounted in the SiP to be integrated in the SiP, and a first planar conductor having at least one slit formed therein. Therefore, the present invention minimizes the amount of current or electromagnetic field induced on the conductor by the current or electromagnetic field of the antenna, thus reducing the influence of the conductor on the operating characteristics of the antenna.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates, in general, to a System-in-Package (SiP) having reduced influence between a conductor and an antenna, and a method of designing the SiP, and, more particularly, to a SiP, which can reduce the influence of a planar conductor on the operating characteristics of an antenna in a SiP in which the antenna is integrated, and a method of designing the SiP. 
   2. Description of the Related Art 
   Recently, in mobile devices, such as mobile phones and Personal Digital Assistants (PDAs), technology for System-in-Package (SiP), in which various systems and passive devices are implemented in the form of a single package to realize the small size of the mobile devices, and in which an antenna for data transmission/reception is also integrated in the package, has been variously used. 
   For example, a Radio-Frequency Identification (RFID) system has been widely used for traffic cards, entrance control cards, etc. Recently, a mobile RFID system has been standardized, and the necessity to mount an RFID reader in a mobile device has increased, so that the importance of SiP technology has gradually increased in order to reduce the size of a large RFID reader. 
     FIG. 1  is a view showing the structure of a conventional RFID reader package. 
   As shown in  FIG. 1 , an RFID reader package is typically implemented in a four-layer structure. That is, the RFID reader package is composed of a top layer  102 , on which a plurality of chips and passive devices is mounted, a bottom layer  104  connected to ball or lead frames required to mount the package on a test board, a power layer  106  for supplying power to the chips and devices in the package, and a ground layer  108  for grounding. 
   In typical cases, as shown in  FIG. 1 , conductors for supplying power and providing ground are formed both on the power layer  106  and on the ground layer  108  in the shape of planes, rather than lines, in order to realize power integrity. 
   The term ‘power integrity’ means the pure and stable supply of the power and ground to prevent noise from occurring in the power and the ground. In order to stably supply power and provide ground, which are Direct Current (DC) voltages, and to decrease DC loss, it is preferable that a power conductor and a ground conductor be implemented in the shape of small planes, having a low impedance value, rather than the shape of lines, having a high impedance value, from the standpoint of power integrity. 
     FIGS. 2A and 2B  are views showing an example in which a conventional RFID reader, in which an antenna is also integrated, is implemented in the form of a SiP. 
     FIG. 2A  is a plan view of an RFID reader SiP in which an antenna is integrated, and  FIG. 2B  is a sectional view thereof. Referring to  FIG. 2A , an antenna  202  is integrated on the top layer of the package and has a spiral shape. Meanwhile, as shown in  FIG. 2B , the above-described conductors  204  and  206  for power and ground are disposed below the antenna  202 . In this case, the power and ground conductors  204  and  206  negatively influence the antenna  202  in such a way that an electric field and a magnetic field are induced on the conductors  204  and  206 , and thus eddy current is generated. 
   Therefore, in order to decrease the influence between the conductors  204  and  206  and the antenna  202 , a structure in which magnetic material, such as a ferrite  208 , is interposed between the antenna  202  and the conductors  204  and  206  has been proposed. However, a package having such a structure is also problematic in that the operating characteristics desired by the antenna cannot be exhibited in simulation and measurement, and the size of the package is increased. 
     FIGS. 3A and 3B  are views showing comparison results obtained through the simulation of the influence on the antenna in a conventional RFID reader SiP, in which the antenna is integrated. 
     FIG. 3A  illustrates magnetic flux density distribution, which is the result of the simulation of an antenna in a free space, and  FIG. 3B  illustrates magnetic flux density distribution obtained when a metal plane is disposed below the antenna. 
   When the antenna is disposed in a free space, as shown in  FIG. 3A , it can be seen that the magnetic flux density is regularly distributed above and below the antenna. However, when the metal plane is disposed below the antenna, as shown in  FIG. 3B , the antenna on the metal plane is influenced by the metal plane, so that the magnetic flux density is strongly distributed only in the direction in which the metal plane is placed, and thus the characteristics of the antenna, which must have excellent radiation characteristics, are deteriorated. That is, it can be seen that, when an antenna is integrated in a package, a conductor plane placed below the antenna very negatively influences the operating characteristics of the antenna. 
   Therefore, a package design method for preventing an influence from being exerted on an antenna that is integrated in the package, as a result of the design itself of the package, is required, in addition to the insertion of magnetic material, such as a ferrite. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a SiP having reduced influence between a conductor and an antenna, which can minimize an electromagnetic field induced on a planar conductor in a SiP in which the antenna is integrated, thus reducing the influence of the conductor on antenna characteristics. 
   In accordance with one aspect of the present invention to accomplish the above object, there is provided a System-in-Package (SiP) having a reduced influence between a conductor and an antenna, comprising an antenna configured to function to transmit or receive data and mounted in the SiP to be integrated in the SiP; and a first planar conductor having at least one slit formed therein. 
   In accordance with another aspect of the present invention to accomplish the above object, there is provided a planar conductor for a System-in-Package (SiP), comprising at least one slit formed therein to reduce current or an electromagnetic field induced on the conductor by current or an electromagnetic field of an antenna integrated in the SiP. 
   In accordance with a further aspect of the present invention to accomplish the above object, there is provided a method of designing a System-in-Package (SiP) having a reduced influence between a conductor and an antenna, comprising forming at least one slit in a first planar conductor included in the SiP to reduce current or an electromagnetic field induced on the conductor by current or an electromagnetic field of the antenna integrated in the SiP. 
   In accordance with yet another aspect of the present invention to accomplish the above object, there is provided a System-in-Package (SiP) having a reduced influence between a conductor and an antenna, comprising an antenna configured to function to transmit or receive data and mounted in the SiP to be integrated in the SiP; and a layer for supplying power or providing ground through a linear conductor. 
   In accordance with still another aspect of the present invention to accomplish the above object, there is provided a method of designing a System-in-Package (SiP) having a reduced influence between a conductor and an antenna, comprising allowing power to be supplied or ground to be provided into the SiP through a linear conductor. 
   In accordance with still another aspect of the present invention to accomplish the above object, there is provided a System-in-Package (SiP) having reduced influence between a conductor and an antenna, comprising an antenna configured to function to transmit or receive data and mounted in the SiP to be integrated in the SiP; and a planar conductor having a cutout formed therein at a feeding point of the antenna. 
   In accordance with still another aspect of the present invention to accomplish the above object, there is provided a method of designing a System-in-Package (SiP) having a reduced influence between a conductor and an antenna, comprising forming a cutout in a planar conductor, included in the SiP, at a feeding point of an antenna integrated in the SiP. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a view showing the structure of a conventional RFID reader package; 
       FIGS. 2A and 2B  are views showing an example in which a conventional RFID reader, in which an antenna is also integrated, is implemented in the form of a SiP; 
       FIGS. 3A and 3B  are views showing comparison results obtained through the simulation of the influence on the antenna in a conventional RFID reader SiP, in which the antenna is integrated; 
       FIGS. 4A and 4B  are views showing a mechanism in which an antenna induces current on a conductor in a conventional SiP; 
       FIG. 5  is a view showing a structure in which current, induced by an antenna, is cut off by a slit formed in a conductor in a SiP according to an embodiment of the present invention; 
       FIGS. 6A and 6B  are views showing an antenna and a conductor having slits formed therein in a SiP according to an embodiment of the present invention; 
       FIGS. 7A and 7B  are views showing conductors, having slits symmetrically and asymmetrically formed therein, in a SiP according to an embodiment of the present invention; 
       FIG. 8  is a view showing a structure in which power and ground are supplied in a linear shape in a SiP according to an embodiment of the present invention; 
       FIG. 9  is a view showing the distribution of the magnitude of surface current induced by an antenna on a conductor in a conventional SiP; and 
       FIGS. 10A and 10B  are views showing the formation of a cutout in a conductor in a SiP according to an embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. Further, detailed descriptions may be omitted if it is determined that the detailed descriptions of related well-known functions and construction may make the gist of the present invention unclear. 
     FIGS. 4A and 4B  are views showing a mechanism in which an antenna induces current on a conductor in a conventional SiP. 
     FIG. 4A  shows the case where an antenna  402  is placed on the top surface of a SiP package, and a planar conductor  404  is placed below the antenna  402  when current Iantenna flows through the antenna  402 . 
   In this case, a magnetic flux density (H-field) is induced in the direction indicated in the drawing by the current lantenna flowing through the antenna  402  depending on the direction of the current lantenna. The magnetic flux density induces current linduced on the planar conductor  404 , placed below the antenna, in the direction indicated in the drawing. The directivity, in which the current linduced is induced, is obtained by Maxwell&#39;s equation, which is a basic equation in the electromagnetic field, and is shown in  FIG. 4B  in a sectional view. 
   In this way, electromagnetic waves radiated from the antenna induce eddy current on the conductor, and thus negatively influence the performance of the antenna. Accordingly, there is a need to prevent the current induced by the antenna. 
     FIG. 5  is a view showing a structure in which current induced by an antenna is cut off by a slit formed in a conductor in a SiP according to an embodiment of the present invention. 
   Referring to  FIG. 5 , a magnetic flux density (H-field) is induced by current I-antenna flowing through an antenna  502 , similar to  FIG. 4A , and then induces current linduced on a planar conductor  504  placed below the antenna  502 . However, when a slit  506  is formed in the planar conductor  504 , as shown in  FIG. 5 , the current linduced on the planar conductor  504  is cut off by the slit  506 , thus decreasing the magnitude of the induced current linduced. 
   That is, the induced current Iinduced is cut off by the slit  506  formed in the planar conductor  504 , and is formed to be smaller than that of the case in which no slit is formed, as shown in  FIG. 4A . In this case, the direction in which the slit is formed in the planar conductor  504  may be preferably taken to be perpendicular to the direction of current flowing through the antenna  502 , as shown in  FIG. 5 . 
     FIGS. 6A and 6B  are views showing an antenna and a conductor having slits formed therein in a SiP according to an embodiment of the present invention. 
     FIG. 6A  illustrates an antenna  602  integrated in a SiP. In  FIG. 6A , the antenna  602  is integrated and has a spiral shape. Moreover, antennas having various shapes can be formed. 
     FIG. 6B  illustrates slits  606  formed in a planar conductor  604  in a SiP. Referring to  FIGS. 6A and 6B , the slits  606  are formed in the shape of a plus sign without a central portion to be perpendicular to the direction of the current path of the antenna  602  so as to reduce induced current. Of course, the shape of the slits shown in  FIG. 6B  is only an example, and it will be apparent to those skilled in the art that various modifications are possible. That is, the shape and number of slits can be determined in various forms depending on the shape of the antenna included in the SiP. 
     FIGS. 7A and 7B  are views showing conductors, having slits symmetrically or asymmetrically formed therein, in a SiP according to an embodiment of the present invention. 
     FIG. 7A  illustrates the case where slits  706  are symmetrically formed in the conductors  702  and  704  of a SiP according to an embodiment of the present invention. For example, as shown in  FIG. 7A , the plus sign-shaped slits  706  may be symmetrically formed in planar conductors  702  and  704 , respectively formed on a power layer for supplying power and a ground layer for providing ground. When slits are symmetrically formed in this way, current induced by the antenna can be cut off double. 
     FIG. 7B  illustrates the case where slits  706  are asymmetrically formed in conductors  702  and  704  in a SiP according to an embodiment of the present invention. For example, as shown in  FIG. 7B , slits  706 , having the shape of a plus sign without a central portion, can be formed in the conductor  702  on a power layer, and slits  706  can be formed in the conductor  704  on a ground layer in shapes other than the shape of a plus sign without a central portion. When the slits are asymmetrically formed in this way, a complementary effect can be expected to enable induced current, which cannot be sufficiently cut off by the slits of any one conductor, to be completely cut off by the slits of the remaining conductor. 
     FIG. 8  is a view showing a structure in which power and ground are supplied in a linear shape in a SiP according to an embodiment of the present invention. 
   As described above, it can be seen that a planar conductor placed in a SiP very badly influences the operating characteristics of an antenna, as shown in  FIGS. 3A and 3B , and that the operating characteristics of the antenna are excellent when the planar conductor is completely removed. Therefore, the removal of the planar conductor may be the best solution, but, if the planar conductor cannot be completely removed, a conductor may be formed in a linear shape, rather than a planar shape, thus decreasing the influence of the conductor on the antenna. 
   Referring to  FIG. 8 , it can be seen that all planar conductors placed on power and ground layers are removed, and only required parts of the conductors are formed in linear shapes, and thus power and ground are supplied. 
     FIG. 9  is a view showing the distribution of the magnitude of surface current induced by an antenna on a conductor in a conventional SiP. 
   Referring to  FIG. 9 , the distributions of magnitudes of surface currents, induced by electromagnetic waves radiated from an antenna  902  on the surface of a planar conductor  900 , when the planar conductor  900  is placed below the antenna  902  integrated in a SiP, are indicated by different colors. As shown in  FIG. 9 , the portion most influenced by the electromagnetic waves attributable to the antenna  902  (red portion) is the feeding point  904  of the antenna  902 . Therefore, a method of sufficiently decreasing the influence of induced current around the feeding point  904  is required, and is described with reference to  FIGS. 10A and 10B . 
     FIGS. 10A and 10B  are views showing the formation of a cutout in a conductor in a SiP according to an embodiment of the present invention. 
   Referring to  FIG. 10A , a planar conductor  1000  is placed below an antenna  1002  integrated in a SiP, and a feeding point  1004  is connected to the antenna  1002 . 
   As described above with reference to  FIG. 9 , since the influence of induced current is greatly exerted around the feeding point  1004  of the antenna  1002 , it will be efficient to eliminate part of the conductor  1000  present around the feeding point  1004 . Therefore, part of the conductor  1000  present around the feeding point  1004  is cut away, that is, a cutout is formed, and thus the influence of the induced current around the feeding point  1004  can be decreased. 
     FIG. 10B  shows that a cutout  1006  is formed in a conductor  1000  near the feeding point  1004 . In  FIG. 10B , the corner of the conductor  1000  is cut away to form the cutout, but it will be apparent that this structure is only an example, and that the shape and size of the cutout can be variously modified. 
   Meanwhile, in the SiP according to the embodiments of the present invention, described with reference to  FIGS. 6 to 10 , an example in which both a slit and a cutout can be formed together in the conductor so as to decrease the influence of induced current can be presented as another embodiment of the present invention, wherein the application of both a slit and a cutout is obvious, and thus a detailed description thereof is omitted. 
   Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but are intended to describe the invention. The technical spirit of the present invention is not limited to such embodiments. The scope of the present invention must be defined by the following claims, and all equivalents thereof should be interpreted as being included in the technical spirit and scope of the present invention. 
   According to the SiP having reduced influence between a conductor and an antenna, and a method of designing the SiP, there are advantages in that a slit or a cutout is formed in the planar conductor of the SiP, or alternatively a conductor is formed in a linear shape, rather than a planar shape, so that the amount of current or the electromagnetic field induced on the conductor by the electromagnetic field of the antenna is minimized, thus greatly decreasing the influence of the conductor on the operating characteristics of the antenna.