Patent Publication Number: US-6992633-B2

Title: Multi-band multi-layered chip antenna using double coupling feeding

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a multi-band multi-layered chip antenna, which can be mounted in GSM (Global System for Mobile communication), DCS (Digital Europe Cordless Telephone) and BT (Bluetooth) terminals, and particularly to a multi-band multi-layered chip antenna using double coupling feeding, which realizes multi-band characteristics using a feeding radiation element and double parasitic radiation elements in the chop antenna, so that with impedance adjustment between the double parasitic elements, control of frequency and bandwidth, enhancement of impedance characteristics and radiation efficiency, and minimized influence of mutual impedance between the radiation elements can be realized. 
   2. Description of the Related Art 
   In general, as for an antenna applicable to mobile communication terminals, such as GSM, DCS, BT and the like, a helical antenna formed as an outward protrusion on the communication terminal or a linear monopole antenna retractable into the communication terminal are mainly used. Although such a helical antenna or a monopole antenna has an advantage of a non-directional radiation characteristic, since these antennas are an external type in which the antenna is protruded outward from the terminal, there are worries about damage of an appearance due to an external force, leading to deterioration of the characteristics, and these antennas have a low Specific Absorption Rate (SAR), which has been proposed recently. 
   Meanwhile, recent requirements of the mobile communication terminals are miniaturization, lightweight and multi-functionality. In order to satisfy these requirements, built-in circuits and components to be employed in the communication terminal also have tendencies toward the miniaturization as well as the multi-functionality. These tendencies of miniaturization and multi-functionality are also required of the antenna, one of the most important components of the communication terminal. 
   As for conventional built-in type antennas, there are micro-strip patch antennas, planar inverted F-type antennas, chip antennas, and the like. There are suggested methods of effectively miniaturizing these built-in type antennas. For instance, there is a method by which the micro-strip patch antenna having a relatively high gain and wide bandwidth characteristics is reduced in size using an aperture coupled feeding structure. According to this method, with an electric field distribution of TM 01  mode of the micro-strip patch antenna, the dielectrics are inserted in the longitudinal direction of a resonance patch to a lower portion of an edge of the patch where the electric field distribution is highest, effectively reducing the size of the antenna and minimizing gain reduction in the antenna, which can occur due to an increase of the dielectric constant, thereby providing a lightweight, miniaturized antenna. 
   However, since the method of miniaturizing the currently available antenna is based on a planar structure, there is a limitation in miniaturization, and when considering the current tendency of reducing space for the antenna to be mounted in a PDA (Personal Digital Assistant) caused by an increase in service of the PDA, there is a need to provide an enhanced method. 
   Further, although inverse L-type, inverse F-type and the like are used as feeding type antennas used in the conventional antennas, there is a need to enhance the feeding type in view of space efficiency. 
     FIG. 1  is a perspective view illustrating the structure of a conventional multi-layered chip antenna. 
   The conventional multi-layered chip antenna shown in  FIG. 1  is an antenna miniaturized such that the antenna can be used in the multi-band, in which first and second radiation patches  30  and  40  of the antenna are coupled to each other via a feeding part  20  at an upper portion of one edge of a ground metal plate  10 , and the feeding part  20  is coupled to the ground metal plate  10  in the perpendicular direction. 
   The first radiation patch  30  defining the top surface of the antenna has a labyrinth-shaped fold slit patch structure, and is parallel to the planar upper surface of the ground metal plate  10 . 
   The second radiation patch  40  is positioned between the first radiation patch  30  and the ground metal plate  10  while being parallel to the first radiation patch  30  and the ground metal plate  10 . The secondary radiation patch  40  comprises a plurality of strip patches  41  and  43  having lengths and widths different from each other, respectively, and each of the strip patches  41  and  44  can be positioned on an identical plane, or can be laminated with each other. 
   The feeding part  20  comprises a feeding pattern  21 , a feeding pattern extension  22 , a feeding pattern ground portion  23 , and the like. The feeding pattern  21  acts to transmit signals between a body of the PDA and the first and second radiation patches  30  and  40  of the antenna, and is perpendicularly coupled to a feeding metal conductor provided at one side of the ground metal plate  10 . The feeding pattern extension  22  extends perpendicular to the feeding pattern  21  from a predetermined portion of the feeding pattern  21 , and the length of the feeding pattern extension  21  can be varied. The feeding pattern extension  22  is bent toward the ground metal plate  10  at the end of the feeding pattern extension  22 , grounded to the ground metal plate  10 . 
   Meanwhile, although the conventional multi-layered chip antenna can be available in multi-band and have a miniaturized structure, there are problems as follows. 
   First, since the first radiation patch  30  constituting the antenna has patterns, almost all of which are formed on one plane, and the second radiation patch  40  has the other patterns, almost all of which are formed on the other plane, there is a problem in that the miniaturization of the antenna is limited. 
   Further, since both patterns of the first and second radiation patches  30  and  40  constituting the antenna respectively have shapes of a substantially straight line, there is a problem in that the miniaturization of the antenna is limited. 
   Additionally, since both the first and second radiation patches are directly coupled to the feeding line, if there is a need to adjust a frequency due to a process variation after manufacturing the antenna according to a predetermined design, change of one patch has a direct influence on the other patch connected to the patch, thereby making frequency operation difficult. 
   SUMMARY OF THE INVENTION 
   The present invention has been made to solve the above problems, and it is an object of the present invention to provide a multi-band multi-layered chip antenna using double coupling feeding, which realizes multi-band characteristics using a feeding radiation element and double parasitic radiation elements of a chip antenna, so that controls of frequency and bandwidth, enhancement of impedance characteristics and radiation efficiency, and minimized influence of mutual impedance between the radiation elements can be realized through impedance adjustment between the double parasitic elements. 
   In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a multi-band multi-layered chip antenna using double coupling feeding, comprising: a first feeding radiation element including a first feeding electrode connected at one side of the first feeding electrode to a feeding line and connected at the other side thereof to a ground surface while being formed on a first plane in a predetermined direction, the first feeding radiation element being connected to the first feeding electrode so that the first feeding radiation element has a spatial meander line structure; a second feeding radiation element connected to a portion of the first feeding electrode on a second plane parallel to the first plane so that the second feeding radiation element has a planar meander line structure; a second feeding electrode connected to a portion of the first feeding electrode on a third plane parallel to the first plane; a first parasitic radiation element electrically coupled to the second feeding electrode; and a second parasitic radiation element electrically coupled to the first parasitic radiation element and comprising a plurality of parasitic patterns. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and features 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 perspective view illustrating the structure of a conventional multi-layered chip antenna; 
       FIG. 2  is a perspective view illustrating the structure of a multi-layered chip antenna according to the present invention; 
       FIG. 3  is a front view of the multi-layered chip antenna of  FIG. 2 ; 
       FIG. 4  is a perspective view of a first feeding radiation element of the present invention; 
       FIG. 5  is an enlarged perspective view illustrating a portion A of  FIG. 4 ; 
       FIG. 6  is a perspective view of a second feeding radiation element of the present invention; 
       FIG. 7  is a perspective view of double parasitic elements of the present invention; 
       FIG. 8  is an enlarged perspective view illustrating a portion B of  FIG. 7 ; and 
       FIGS. 9   a  and  9   b  are graphical representations of VSWR characteristic of the chip antenna according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments will now be described in detail with reference to the accompanying drawings. 
   Like components, which have substantially identical structures and functions, will be denoted by like reference numerals. 
   A multi-layered chip antenna of the present invention is not a general PIFA-type antenna but a built-in type multi-layered ceramic chip antenna, wherein a GSM band is basically realized using a meander line and an inverse F-type provided in the chip antenna and a DCS band is realized using parasitic elements provided at the upper layer of the antenna. Further, the multi-layered chip antenna of the present invention has advantages in that with a structural modification for adjusting coupling of the parasitic elements at the upper layer, embodiment of triple bands, adjustment of a central frequency, and enlargement of the bandwidth can be realized. 
     FIG. 2  is a perspective view illustrating the structure of a multi-layered chip antenna according to the present invention, and  FIG. 3  is a front view of the multi-layered chip antenna of  FIG. 2 . 
   Referring to  FIGS. 2 and 3 , the multi-layered chip antenna according to the present invention comprises: a first feeding radiation element  100  including a first feeding electrode  110  connected at one side of the first feeding electrode to a feeding line and connected at the other side thereof to a ground surface while being formed on a first plane in a predetermined direction, the first feeding radiation element being connected to the first feeding electrode so that the first feeding radiation element has a spatial meander line structure; a second feeding radiation element  200  connected to a portion of the first feeding electrode  110  on a second plane parallel to the first plane so that the second feeding radiation element has the a planar meander line structure; a second feeding electrode  300  connected to another portion of the first feeding electrode  110  on a third plane parallel to the first plane; a first parasitic radiation element  400  electrically coupled to the second feeding electrode  300 ; and a second parasitic radiation element  500  electrically coupled to the first parasitic radiation element  400  and comprising a plurality of parasitic patterns  510 – 590  and  595 . 
   The multi-band chip antenna of the present invention comprises the feeding radiation elements  100  and  200  and double parasitic radiation elements  400  and  500 , by which resonance frequencies of GSM, DCS, and BT are generated, respectively. Further, the multi-band chip antenna of the present invention improves the bandwidth in a single frequency by adjoining the resonance frequencies thereof to each other. Specifically, the multi-band chip antenna comprises the second feeding radiation element  200  having the meander line structure for providing a GSM band of 880˜960 MHz and a Bluetooth band of 2.4˜2.48 GHz, the first feeding radiation element  100  having an inverse F structure and the spatial meander line structure, and double parasitic radiation elements  400  and  500  for providing a DCS band of 1,710˜1,880 MHz. 
   Here, the second feeding radiation element  200  has the meander line structure, in which the frequency can be adjusted by controlling a width and a space of the lines in this structure. Further, the first feeding radiation element  100  has the inverse F structure and the spatial meander line structure, in which the operating frequency can be adjusted by controlling a width of the lines in these structures. 
   Thus, the GSM band of 880˜960 MHz and the Bluetooth band of 2.4˜2.48 GHz are provided by a combined structure of the meander line structure of the second feeding radiation structure  200 , and the inverse F structure and the meander line structure of the first feeding radiation structure  100 . 
     FIG. 4  is a perspective view of the first feeding radiation element of the present invention. 
   Referring to  FIG. 4 , the first feeding radiation element  100  is parallel to the first feeding electrode  110 , and comprises a plurality of strip lines  120  ( 120   a  ˜ 120   m ) spaced from each other by a predetermined distance while being parallel to each other, a first connecting pattern  131  for connecting one strip line  120   a  adjacent to the first feeding electrode  110  among the plurality of strip lines  120  to the first feeding electrode  110 , and a second connecting pattern  132  comprising a plurality of patterns  132   a  ˜ 132   l , which respectively connect two adjoining strip lines among the plurality of strip lines  120 , thereby forming the meander line structure. 
   Here, the first connecting pattern  131  and the second connecting pattern  132  are formed on the plane different from the first plane while being parallel to the first plane. That is, as shown in  FIGS. 2 and 4 , the connecting patterns for connecting the plurality of strip lines are formed on the plane different from the first plane on which the strip lines are formed, so that the first feeding radiation element  100  forms the spatial meander line structure. 
   The first feeding electrode  110  of the first feeding radiation element  100  is connected at one side of the first feeding electrode  110  to the feeding line, and connected at the other side thereof to the ground plane. The first feeding electrode  110  comprises two feeding patterns  111  and  112  parallel to the first plane, and a feeding connecting pattern  113  for connecting adjacent ends of the feeding patterns  111  and  112 . The first feeding electrode  110  has the inverse F shape. 
     FIG. 5  is an enlarged perspective view illustrating a portion A of  FIG. 4 . 
   Referring to  FIG. 5 , the first connecting pattern  131  of the first feeding radiation element  100  comprises a first vertical connecting pattern  1311  formed upward from the end of the first feeding electrode  110 , a second vertical connecting pattern  1311  formed upward from the end of the strip line  120   a  adjacent to the first feeding electrode among the plurality of strip lines  120   a  ˜ 120   m , and a horizontal connecting pattern  1313  connecting the first and second vertical connecting patterns  1311  and  1312  on the plane different from the first plane while being parallel to the first plane. 
   Further, referring to  FIG. 5 , the second connecting pattern  132  of the first feeding radiation element  100  comprises a plurality of vertical connecting patterns  1321  formed upward from each end of the plurality of strip lines  120   a  ˜ 120   m , a plurality of horizontal patterns connecting two adjacent vertical patterns to each other as a pair of the vertical patterns among the plurality of vertical connecting patterns  1321  on the other plane parallel to the first plane. The plurality of horizontal patterns are a plurality of horizontal connecting patterns  1322 , which do not overlap and/or connect to each other but are separated from each other in a zigzag shape. 
   The plurality of horizontal connecting patterns  1322  of the first feeding radiation element  100  is formed on the plane between the second plane formed with the second feeding radiation element  200  and the third plane formed with the second feeding electrode  300 . Further, the horizontal connecting patterns  1322  of the first feeding radiation element  100  can be formed in a non-linear pattern or in a linear pattern. 
     FIG. 6  is a perspective view of the second feeding radiation element of the present invention. 
   Referring to  FIG. 6 , the second feeding radiation element  200  comprises a feeding pattern  210  connected to one pattern of the first feeding element  110  and a radiation pattern  220  connected to the other pattern  112  of the first feeding element  110  to have the meander line structure. 
   Further, the second feeding electrode  300  is formed in parallel to one feeding pattern  111  of the first feeding element  110  in the same direction as that of one feeding pattern  111  on the plane different from the first plane while being parallel to the first plane. 
     FIG. 7  is a perspective view of the double parasitic radiation element of the present invention. 
   As shown in  FIG. 7 , the first parasitic radiation element  400  is formed perpendicular to the second feeding electrode  300 , thereby forming a first coupling along with the second feeding electrode  300 . The second parasitic radiation element  500  is formed perpendicular to the first feeding electrode  400 , thereby forming a second coupling along with the first parasitic radiation element  400 . 
     FIG. 8  is an enlarged perspective view illustrating a portion B of  FIG. 7 . 
   Referring to  FIG. 7 , the plurality of parasitic patterns  510 ˜ 590  and  595  of the second parasitic radiation element  500  comprise lower patterns  502  formed at a lower part of the first parasitic radiation element in the perpendicular direction to the first parasitic radiation element  400 , respectively. 
   Further, in addition to the lower pattern  502  formed at the lower part of the first parasitic radiation element  400  in the direction perpendicular to the first parasitic radiation element  400 , each of the plurality of parasitic patterns  510 ˜ 590  and  595  of the second parasitic radiation element  500  comprises: both sides patterns  501  including first and second patterns  501   a  and  501   b  spaced from the first parasitic radiation element  400  by a predetermined distance at either side of the first parasitic radiation element  400  while having a predetermined length, respectively, in the direction perpendicular to the first parasitic radiation element  400 ; a first connecting pattern  503  connecting one end of the first pattern  501   a  and one end of the lower pattern  502  so that they are perpendicular to each other; and a second connecting pattern  504  connecting one end of the second pattern  501   b  and the other end of the lower pattern  502  so that they are perpendicular to each other. 
   Here, the second parasitic radiation element  500  has a structure for realizing a second coupling feeding. For instance, the coupling can be controlled only with the lower patterns  502  perpendicularly formed at the lower part of the first parasitic radiation element  400 . Further, it is desirable that second parasitic radiation element  500  further comprises both sides patterns  501  connected to the lower patterns  502  via the first and second connecting patterns  503  and  504 . With the coupling having the above structure, the bandwidth in the DCS band, the radiation characteristics, the impedance between parasitic elements, and the total impedance of the antenna can be adjusted. 
   Here, the plurality of parasitic patterns  510 ˜ 590  and  595  of the second parasitic radiation element  500  can be uniformly spaced from each other. 
   That is, referring to  FIGS. 7 and 8 , the first and second parasitic radiation elements  400  and  500  of the present invention are the parasitic radiation elements for providing the DCS band. The first parasitic radiation element  400  is extended in the lengthwise direction of the antenna, whereas the plurality of parasitic patterns  510 ˜ 590  and  595  of the second parasitic radiation element  500  are uniformly spaced from each other centering on the first parasitic radiation element  400  while being perpendicular to the first parasitic radiation element  400 . 
   The first parasitic radiation element  400  is coupled to the second feeding electrode  300 , which is connected to the first feeding electrode via a feeding via hole, and resonates in the DCS band, of which the central frequency can be adjusted by controlling the spaces between the plurality of parasitic patterns of the second parasitic radiation element  500  perpendicular to the first parasitic radiation element  400  and the number of the parasitic patterns of the second parasitic radiation element  500 . 
   Further, referring to  FIGS. 7 and 8 , the first and second parasitic radiation elements of the present invention are the parasitic radiation elements for realizing the DCS band. Unlike a feeding radiation element for controlling an operating frequency according to a length of the conductor&#39;s pattern (that is, Inductance), the first and second parasitic radiation elements of the present invention can adjust the frequency using the coupling (that is, Capacitance) in order to realize the DCS band. That is, since electric current is induced in the first parasitic radiation element  400  by mutual coupling (a first coupling feeding), inductance can be adjusted with the second parasitic radiation element formed perpendicular to the first parasitic radiation element  400  to form capacitance together with the first parasitic radiation element  400 , and thus the operating frequency can be controlled therewith. 
   When the DCS band is realized using the double parasitic radiation elements consisting of the first and second parasitic radiation elements  400  and  500 , for instance, when the DCS band is realized using the radiation element connected to the feeding electrode, change of one feeding radiation element can prevent a total impedance of the antenna from being deformed, and the central frequency can be easily provided and controlled with an influence of the mutual impedance between the radiation elements. As a result, when realizing the double parasitic radiation elements, not only can control of frequency and the central frequency be obtained through a structural modification (such as dimension, shape and the number) of the parasitic element only in consideration of the mutual impedance caused by the parasitic element, but the bandwidth can also be widened using the coupling. 
   Further, the bandwidth can be adjusted by varying the number of the plurality of parasitic patterns  510 ˜ 590  and  595  of the second parasitic radiation element  500 , and the operating frequency can be controlled by adjusting the space between the parasitic elements formed in the perpendicular direction, with the plurality of parasitic patterns  510 – 590  and  595  maintained in an identical structure in the lengthwise direction. For instance, the space of the second parasitic element formed in the perpendicular direction can be set in the range of about 2/λ˜8/λ. 
   In the present invention, a bandwidth characteristic of the multi-layered chip antenna according to an increase of the number of the second parasitic radiation elements coupled to the first parasitic radiation element is shown in  FIGS. 9   a  and  9   b.    
     FIGS. 9   a  and  9   b  are graphical representations of a VSWR characteristic of the chip antenna according to the present invention. 
   The VSWR characteristic of the chip antenna of the present invention were measured after mounting the first and second parasitic radiation elements realizing in the DCS bandwidth in a real set, with the GSM and BT bandwidth fixed, and the results are shown in  FIGS. 9   a  and  9   b . The results show that when the chip antenna is mounted in the real set, the operating frequency is varied from the operating frequency designed to operate in respective operating bands. 
     FIG. 9   a  shows the result when using the double parasitic radiation elements of the present invention, by which it can be seen that at a point VSWR[1:1.1480], the frequency formed with an upper pole of the band is at about 1.87 GHz. In  FIG. 9   b , it can be seen that as the number of the second parasitic radiation elements formed in the perpendicular direction is increased, at a point VSWR[2:1.2460], the frequency formed with an upper pole of the band is at about 1.915 GHz, which is higher about 45 MHz, compared with the frequency of  FIG. 9   b.    
   According to the results, the band of the multi-layered chip antenna according to the increase of the number of the second parasitic radiation element coupled to the first parasitic radiation element can be adjusted, and the bandwidth thereof can be widened. 
   Since the feeding radiation element and the parasitic radiation elements are realized in one chip, the ceramic chip antenna of the present invention must adjust difficult characteristics, such as mutual coupling effects, the mutual impedance and the radiation characteristic in each band. Thus, the present invention realizes these characteristics to an applicable level. 
   As apparent from the above description, according to the present invention, there are advantageous effects in that the multi-band multi-layered chip antenna, which can be mounted in the GSM, DCS and BT terminals, realizes the multi-band characteristics using the feeding radiation element and the double parasitic elements of the chip antenna, so that control of the frequency and the bandwidth, enhancement of the impedance characteristics and the radiation efficiency, minimized influence of mutual impedance between the radiation elements can be obtained by adjusting the impedance between the double parasitic elements. 
   It should be understood that the embodiments and the accompanying drawings as described above have been described for illustrative purposes and the present invention is limited by the following claims. Further, those skilled in the art will appreciate that various modifications, additions and substitutions are allowed without departing from the scope and spirit of the invention as set forth in the accompanying claims.