Patent Publication Number: US-2013234897-A1

Title: Mobile terminal apparatus and method for performing wireless communication using an indirect feeding antenna

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2012-0023172, filed on Mar. 7, 2012, the entire disclosure of which is incorporated herein by reference for all purposes. 
     BACKGROUND 
     1. Field 
     Exemplary embodiments relate to mobile terminal apparatuses and methods for performing wireless communication using an indirect feeding antenna to additionally support a desired frequency band. 
     2. Discussion of the Background 
     Development of antenna technologies has contributed to development of small-size, slim mobile communication terminals. 
     Known first-generation mobile communication terminals may have stud type antennas that protrude out of their housings, the stud type antennas may be easily broken and limiting the design of the terminal. 
     However, recently, an antenna, sometimes called an “intenna,” that is installed in a housing to be invisible externally has been introduced and popularized. 
     However, such “intenna” also needs to meet requirements of excellent radiation characteristics and a wide bandwidth while having a small size to be installed in a small-sized, slim mobile communication terminal. Particularly, a space for an antenna gets more limited as mobile terminals get slimmer and smaller and, accordingly, the importance of designing an antenna having excellent characteristics without increasing its size becomes greater. Furthermore, recently developed terminals may need to cover two or more frequency bands. 
     For example, in the case of a mobile communication terminal based on the Long Term Evolution (LTE) technology according to the 3GPP specification, which is a representative 4G mobile communication technology, the mobile communication terminal has to basically support frequency bands of 700 MHz through 960 MHz and 2.5 GHz through 2.7 GHz. 
     In order to support multiple bandwidths with a single antenna, a method of forming a plurality of patterns in a radiating element for transmission/reception to cause double resonance can be used. However, such method may have difficulty in acquiring a wide receiving bandwidth. 
     SUMMARY 
     Exemplary embodiments of the present invention provide apparatuses and methods for performing wireless communication by a mobile terminal apparatus, such as handheld, portable or tablet computer or communication devices, with an indirect feeding sub antenna to support a desired frequency band, such as may be used for voice or data communications. 
     Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. 
     Exemplary embodiments of the invention provide a mobile terminal apparatus with an indirect feeding antenna, capable of supporting multiple frequency bands and a wide frequency band range by additionally supporting a desired second frequency band or bands, as well as a first frequency band or bands supported by a main antenna, by feeding a sub antenna indirectly through coupling with a feeding pad of the main antenna to produce an additional resonance when the main antenna produces a resonance. 
     Exemplary embodiments of the invention provide a mobile terminal apparatus with an indirect feeding antenna, of a multi-band antenna, by producing an additional resonance by a sub antenna without changing a resonance frequency band of a main antenna. 
     The following description also relates to a mobile terminal apparatus with an indirect feeding antenna, capable of providing a sub antenna without increasing the volume of the mobile terminal apparatus by forming the sub antenna in a space or area of the mobile terminal apparatus for a main antenna. 
     Exemplary embodiments of the invention provide a mobile terminal apparatus to perform wireless communication, including a main antenna to transmit or receive signals at one or more first frequency bands, a sub antenna to transmit or receive signals at least at one second frequency band, and a feeding pad connected to the main antenna to directly feed signals to the main antenna to transmit or receive signals at the one or more first frequency bands, the feeding pad being disposed within a reference proximity to and electrically coupled to the sub antenna to indirectly feed signals to the sub antenna to transmit or receive signals in the at least one second frequency band. 
     Exemplary embodiments of the invention further provide a method for performing wireless communication in a mobile terminal apparatus, including feeding signals at one or more first frequency bands directly by a feeding pad to a main antenna to transmit or receive signals at the one or more first frequency bands, and feeding signals at least at one second frequency band indirectly by the feeding pad to a sub antenna, by electrically coupling the feeding pad to the sub antenna disposed within a reference proximity to the feeding pad, to transmit or receive signals in the at least one second frequency band. 
     Exemplary embodiments of the invention additionally provide a method for performing wireless communication in a mobile terminal apparatus, including selectively feeding signals at one or more first frequency bands directly by a feeding pad to a main antenna to selectively transmit or receive signals at the one or more first frequency bands, and selectively feeding signals at least at one second frequency band indirectly by the feeding pad to a sub antenna, by electrically coupling the feeding pad to the sub antenna disposed within a reference proximity to the feeding pad, to selectively transmit or receive signals in the at least one second frequency band. 
     Other features and aspects of exemplary embodiments of the invention will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a plan view of a mobile terminal apparatus with an indirect feeding antenna according to exemplary embodiments of the present invention. 
         FIG. 2  is a perspective view showing an arrangement structure of a main antenna and a sub antenna according to exemplary embodiments of the present invention. 
         FIG. 3  is a perspective view showing an arrangement structure of a main antenna, a sub antenna, and a circuit substrate according to exemplary embodiments of the present invention. 
         FIG. 4  is a perspective view showing an arrangement structure of a main antenna and a sub antenna according to exemplary embodiments of the present invention. 
         FIG. 5  is a perspective view showing the main antenna, the sub antenna, the circuit substrate, and an antenna carrier unit of  FIG. 3  according to exemplary embodiments of the present invention. 
         FIG. 6  is a cross-section view showing the main antenna, the sub antenna, and the circuit substrate of  FIG. 5  according to exemplary embodiments of the present invention. 
         FIG. 7  is a circuit diagram illustrating an example of a mobile terminal apparatus with an indirect feeding antenna according to exemplary embodiments of the present invention. 
         FIG. 8  is a graph showing a VSWR (Voltage Standing Wave Ratio) with respect to frequency of a main antenna that supports multiple bands when no sub antenna is provided as a comparison to exemplary embodiments of the present invention. 
         FIG. 9  is a graph showing a VSWR with respect to frequency when a sub antenna supporting a high frequency band is formed or disposed on a lower face of a circuit substrate through an indirect feeding method according to exemplary embodiments of the present invention. 
         FIG. 10  and  FIG. 11  are graphs showing VSWRs with respect to frequency when a sub antenna supporting a low frequency band is formed or disposed on the lower surface of a circuit substrate through an indirect feeding method according to exemplary embodiments of the present invention. 
     
    
    
     Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience, and should not be construed in a limiting sense. 
     DETAILED DESCRIPTION 
     The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. Also, descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness. 
     It will be understood that when an element is referred to as being “connected to” or “coupled to” another element, it may be directly connected or coupled to the other element or it may be indirectly connected or coupled to another element, or intervening elements may be present. 
       FIG. 1  is a plan view of a mobile terminal apparatus with an indirect feeding antenna according to exemplary embodiments of the present invention. 
     Referring to  FIG. 1 , the mobile terminal apparatus  20  with an indirect feeding antenna includes a main antenna  100  that receives or transmits electromagnetic waves or signals of the corresponding one or more first frequency bands, a circuit substrate  200  on which a circuit for processing signals received/transmitted through the main antenna  100  may be mounted, a feeding pad  300  that connects the main antenna  100  to the circuit substrate  200  directly and may be formed or disposed on the circuit substrate  200 , and a sub antenna  400  spaced apart from or disposed within a reference proximity to the feeding pad  300  in such a way to face the feeding pad  300 , the indirect feeding antenna or sub antenna  400  being indirectly connected by being electrically coupled to the feeding pad  300  for indirect feeding of power or signals to transmit or receive electromagnetic waves or signals at least at one desired second frequency band. 
       FIG. 2  is a perspective view showing an arrangement structure of the main antenna  100  and the sub antenna  400  according to exemplary embodiments of the present invention. 
     In  FIG. 2  circuit substrate  200  is not illustrated for clarity, and the main antenna  100  may be an antenna which resonates in a single frequency band or in multiple frequency bands. If the main antenna  100  supports multiple frequency bands, a plurality of radiating patterns  101  and  102  may be formed or disposed each of which has a length of λ/4 with respect to the wavelength of the corresponding frequency band such that a resonance is caused in each frequency band. The radiating patterns  101  and  102  are used to receive and transmit RF signals, for example. That is, the radiating patterns  101  and  102  resonate in a predetermined resonance frequency band to receive and transmit electromagnetic waves. The radiating patterns  101  and  102  are arranged over the circuit substrate  200 . Also, the radiating patterns  101  and  102  may be spaced apart from or disposed within a reference proximity to the circuit substrate  200  by a distance corresponding to the thickness of an antenna carrier unit  600  (See,  FIG. 5  and  FIG. 6 , for example). The radiating patterns  101  and  102  each may have a structure with at least one bent portion. Here, each of the radiating patterns  101  and  102  may have a meander structure, a spiral structure, a step structure, a loop structure, etc., for example. 
     In order to enable the radiating patterns  101  and  102  to radiate the corresponding frequencies, respectively, the length of the radiating pattern  101  corresponding to a low frequency band may be formed or disposed to be longer than that of the radiating pattern  102  corresponding to a high frequency band, since the length of a radiating pattern is inverse-proportional to frequency magnitude and proportional to wavelength length. Also, the main antenna  100  includes a feeding line  110  connected to the circuit substrate  200  (See  FIG. 1 , for example) to feed the radiating patterns  101  and  102 , and a ground line  120  for grounding the feeding line  110 , wherein the feeding line  110  and the ground line  120  may be integrated into one body. 
     For example, the main antenna  100  may include a low-band radiating pattern  101  that supports a frequency band ranging from 700 MHz to 960 MHz (LTE, CELL, G850, G900), and a high-band radiating pattern  102  that supports a frequency band ranging from 1700 MHz to 2100 MHz (DCS1800/PCS1900/US PCS/WCDMA). 
     The circuit substrate  200  may be used to process signals received/transmitted through the main antenna  100 , and may be a main printed circuit board (PCB) or a sub PCB, for example. The circuit substrate  200  also acts to support electronic components in the mobile terminal apparatus  20 . That is, electronic components, such as, for example, a processor or controller  212 , a memory or storage  216 , a transceiver  216 , and a battery or other power supply  250 , etc., are packaged and supported on the circuit substrate  200 . Also, the circuit substrate  200  may include a ground  240  for grounding the circuit substrate  200  to a board body of the circuit substrate  200 . The various electronic components, structures, and arrangement of the circuit substrate  200  of the mobile terminal apparatus  20 , such as illustrated in  FIG. 1 , are exemplary of any of various suitable arrangements, structures, components and configurations and, therefore, should not be construed in a limiting sense. 
     The processor or controller  212  may include any of various processors, computers or application specific integrated circuits (ASICs) for example, to implement various operations in performing wireless communication by an indirect feeding antenna or sub antenna  400  in a mobile terminal apparatus  20 , as described herein. The memory or storage  214  may include any of various memory or storage media for storing software, program instructions, data files, data structures, and the like. The software, media and program instructions may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may, for example, include hardware, firmware or other modules to perform the operations of the described embodiments of the present invention. 
     The circuit substrate  200  includes a substrate body  205  including a battery or other power supply  250  to supply power to electronic components or elements on the circuit substrate  200 . The substrate body  205  may have a plane structure. One surface of the substrate body  205  may be divided into a ground region  208  and a device region  209 . Also, the substrate body  205  may be made of a dielectric in which a plurality of feeding lines may be included. In this case, the substrate body  205  may be implemented by stacking a plurality of dielectric plates. Also, both ends of each feeding line are exposed to the outside of the mobile terminal apparatus  20 , and one end thereof may be connected to an external power supply. The other end of the feeding line may be exposed to the outside of the mobile terminal apparatus  20  through the device region  209 . Thereby, when power from the external power supply is supplied to the end of the feeding line, the feeding line may transfer the power or signals to its other end. 
     The ground  240  is used to ground the circuit substrate  200 . The ground  240  may be formed or disposed in the ground region  208  of the substrate body  205 . Here, the ground  240  may have a plane structure, and may be formed or disposed horizontally or vertically on one surface of the substrate body  205  in the entire or a part of the ground region  208 . Also, the ground  240  may be implemented as a plane structure in which various shaped grooves or holes are formed or disposed, for example. 
     The feeding pad  300  is formed or disposed on the circuit substrate  200 , and connects the main antenna  100  to the circuit substrate  200 . The main antenna  100  includes the feeding line  110  connected to the feeding pad  300 . 
     The radiating patterns  101  and  102  of the main antenna  100  contact the other end of the feeding line  110 . The feeding pad  300  is formed or disposed at a contact between the radiating patterns  101  and  102  and the feeding line  110 , that is, at one end of the radiating patterns  101  and  102 . The radiating patterns  101  and  102  are grounded by contacting the ground  240 . A ground pad  500 , such as illustrated in  FIG. 3 , may be formed or disposed at a contact between the radiating patterns  101  and  102  and the ground  240 , that is, at the other end of the radiating patterns  101  and  102 . 
     Thereby, when power is supplied from the power supply  250  through the feeding pad  300 , the radiating patterns  101  and  102  resonate in the corresponding resonance frequency band. At this time, a magnetic field may be formed or generated in the peripheral area of the radiating patterns  101  and  102 . 
     The sub antenna  400  is spaced apart from or is disposed within a reference proximity to the feeding pad  300  in such a manner to face the feeding pad  300 , and is indirectly connected to the feeding pad  300  through the electrical coupling for indirect feeding of power or signals indicated at  412 , such as in  FIG. 5 . The sub antenna  400  is coupled with the feeding pad  300  to be fed indirectly. Also, the sub antenna  400  is connected to the ground  240  for matching with the main antenna  100 . The main antenna  100  and the sub antenna  400  may support the same resonance frequency band, or different resonance frequency bands. The sub antenna  400  resonates in the resonance frequency band to receive and transmit RF signals, for example. 
     For example, in order to additionally support the LTE frequency band, the sub antenna  400  may transmit or receive frequency bands of 700 MHz through 900 MHz and 2.5 GHz through 2.7 GHz as resonance frequency bands. Generally, an antenna resonates when it has at least a pattern length of λ/4. For example, in order to configure a sub antenna  400  for a high band of 2.5 GHz through 2.7 GHz, a multi-band antenna having a total pattern length of λ/4 with respect to a frequency band of 2.5 GHz through 2.7 GHz may be configured with the sub antenna  400  on a second or lower surface  202  of the circuit substrate  200  from that of the main antenna  100  on a first or upper surface  201  of the circuit substrate  200  without increasing the volume of the main antenna  100  or modifying the pattern of the main antenna  100 . 
     Meanwhile, in order to configure a sub antenna  400  for a low band of 700 MHz through 900 MHz, a sub antenna  400  having a total pattern length of λ/4 with respect to a frequency band of 700 MHz through 900 MHz may be configured on the other second or lower surface  202  of the circuit substrate  200 . However, since a low frequency band has a longer wavelength than a high frequency band, the low frequency band may have a relatively great influence on the main antenna  100 , which may cause the frequency band of the main antenna  100  to be shifted to the low band or a change in impedance of the main antenna  100 . 
     In order to cause the mobile terminal apparatus  20  antenna or antennas to support a new resonance frequency, it may be typical to configure a new antenna by changing the shape of a main antenna  100 . However, configuring a new antenna may increase the volume of the entire antenna inevitably. Accordingly, as described above, according to exemplary embodiments, by implementing the sub antenna  400  that may be fed indirectly through the feeding pad  300  of the main antenna  100  to cause a resonance in multiple frequency bands and in a wide frequency band range, it may be possible to support a desired frequency band as well as the frequency band of the main antenna  100 , without changing the volume of the main antenna  100 . 
     Also, the main antenna  100  and the sub antenna  400  may be ones selected from among a Planar Inverted-F Antenna (PIFA), a meander antenna, a loop antenna, an Inverted-F antenna, a wire type antenna, etc., according to a communication environment of the corresponding mobile terminal, for example. 
       FIG. 3  is a perspective view showing an arrangement structure of the main antenna  100 , the sub antenna  400 , and the circuit substrate  200  according to exemplary embodiments of the present invention. 
     Referring to  FIG. 1  and  FIG. 3 , the main antenna  100  and the feeding pad  300  may be formed or disposed on the first or upper surface  201  of the circuit substrate  200 , and the sub antenna  400  may be formed or disposed on the second or lower surface  202  of the circuit substrate  200 . The circuit substrate  200  may be generally in the shape of a planar board, and the main antenna  100  may be directly connected to the feeding pad  300 . However, since the sub antenna  400  and the feeding pad  300  may be formed or disposed on different surfaces of the circuit substrate  200 , the sub antenna  400  may not directly connect to the feeding pad  300 . That is, the sub antenna  400  is electrically coupled with the feeding pad  300  through the circuit substrate  200  and fed power or signals indirectly. And the feeding pad  300  may be formed or disposed to feed the main antenna  100 . 
     However, if the thickness of the circuit substrate  200  is sufficiently thin, the sub antenna  400  may be electrically connected to the feeding pad  300  through electrical coupling to be fed power or signals indirectly. If the thickness of the circuit substrate  200  is about 0.3 mm through about 0.5 mm, for example, such indirect feeding of power or signals may be possible. Accordingly, it may be possible to implement the sub antenna  400  in the mobile terminal apparatus  20  without providing a separate feeding line (that is, a feeding pad) for supplying power or signals to the sub antenna  400 , and also to receive and transmit data signals or voice signals in the at least one resonance frequency band of the sub antenna  400 , as well as in the one or more resonance frequency bands of the main antenna  100 . 
     According to exemplary embodiments, the sub antenna  400  and the main antenna  100  may be formed or disposed in substantially parallel or in facing relation to face each other in the upper and lower surfaces or first and second surfaces  201  and  202  of the circuit substrate  200 . In this case, the radiating patterns  101  and  102  of the main antenna  100  may overlap the radiating pattern of the sub antenna  400 , and it may be preferable or desirable that the sub antenna  400  may be applied to support an additional frequency band for a high frequency band, for example. 
     If the sub antenna  400  supports a high frequency band, the length of the radiating pattern of the sub antenna  400  may be reduced, so that an area where the radiating pattern  402  of the sub antenna  400  overlaps the radiating patterns  101  or  102  of the main antenna  100  also may be minimized. Accordingly, since interference of the sub antenna  400  with respect to the main antenna  100  may be minimized, the configuration described above may be preferably or desirably applied to the sub antenna  400  supporting a high frequency band. Meanwhile, if the sub antenna  400  supports a low frequency band, the radiating pattern  402  of the sub antenna  400  may be lengthened relative to a length of at least one radiating pattern  101  or  102  of the main antenna  100 , so that an area where the radiating pattern of the sub antenna  400  overlaps the radiating patterns of the main antenna  100  may also be widened. Accordingly, a possibility may exist that radiation of the sub antenna  400  may cause interference of the main antenna  100  to increase. 
       FIG. 8  is a graph showing a VSWR (Voltage Standing Wave Ratio) with respect to frequency of the main antenna  100  that supports multiple bands when no sub antenna  400  is provided as a comparison with exemplary embodiments of the present invention. 
       FIG. 9  is a graph showing a VSWR with respect to frequency when the sub antenna  400  supporting a high frequency band is formed or disposed on the a lower or second surface  202  of the circuit substrate  200  through an indirect feeding method according to exemplary embodiments of the present invention. 
     As to  FIG. 9 , the circuit substrate  200  may be a main printed circuit board (PCB)  210  or a sub PCB  230  (See  FIG. 1 , for example). Exemplary embodiments where the sub antenna  400  is formed or disposed on the rear surface of the sub PCB  230  on circuit substrate  200  are described below. 
     Referring to  FIG. 8 , when only a main antenna  100  is provided, antenna efficiency may be maintained only in a frequency band ranging from about f 5  to f 6 , and antenna efficiency in a frequency band ranging from about f 7  to f 8  may be very low. Meanwhile, referring to  FIG. 9 , when a sub antenna  400  is provided, antenna efficiency in the frequency band from about f 7  to f 8 , as well as in the frequency band from about f 5  to f 6 , may be maintained. That is, referring to  FIG. 1 ,  FIG. 2 ,  FIG. 3  and  FIG. 9 , by adding the sub antenna  400  as an indirect feeding antenna to the second or lower surface  202  of the circuit substrate  200 , it may be possible to maintain antenna efficiency in the frequency band from about f 7  to f 8 , as well as in the frequency band from about f 5  to f 6 , without substantially changing or affecting the resonance frequency characteristics of the main antenna  100 . Accordingly, by producing an additional resonance by the sub antenna  400 , without substantially increasing the volume of the main antenna  100 , a multi-band antenna for mobile terminal apparatus  20  may be implemented. 
       FIGS. 10 and 11  are graphs showing VSWRs with respect to frequency when the sub antenna  400  supporting a low frequency band is formed or disposed on the lower or second surface  202  of the circuit substrate  200  through the indirect feeding method according to exemplary embodiments of the present invention. 
     Referring to  FIGS. 10 and 11 , in the case of the sub antenna  400  supporting a low frequency band, if the sub antenna  400  is implemented to have a long wavelength similar to that of the main antenna  100 , the sub antenna  400  may influence the low band resonance frequency of the main antenna  100  to thereby shift the resonance frequency or change the impedance of the main antenna  100 . Accordingly, when the low band resonance frequency of the main antenna  100  may have to be shifted, the sub antenna  400  may be implemented to have a resonance frequency adjacent to the corresponding low band resonance frequency. 
       FIG. 4  is a perspective view showing an arrangement structure of the main antenna  100  and the sub antenna  400  according to exemplary embodiments of the present invention. 
     Referring to  FIG. 4 , the sub antenna  400  is formed or disposed in perpendicular or substantially perpendicular relation to the main antenna  100  so as not to be in substantially facing relation to the main antenna  100 . In  FIG. 4 , for ease of illustration, the circuit substrate  200  is not shown. The arrangement structure shown in  FIG. 4 , where the sub antenna  400  does not substantially overlap the main antenna  100 , and is formed or disposed substantially perpendicular thereto, may be efficiently applied to the case where the frequency band of the sub antenna  400  is a low frequency band. 
     However, the radiating pattern  402  of the sub antenna  400  may have to be lengthened, relative to a length of at least one radiating pattern  101  or  102  of the main antenna  100 . If the sub antenna  400  may have to cover a low frequency band having a relatively long wavelength, the sub antenna  400  may therefor influence the frequency characteristics of the main antenna  100  and may have a high possibility of interfering with the transmission or reception of signals by the main antenna  100 . 
     Accordingly, in such case, increasing a separation distance between the main antenna  100  and the sub antenna  400  may minimize interference between the main antenna  100  and the sub antenna  400 . As illustrated in  FIG. 4 , for example, a feeding part  404  of the sub antenna  400  is formed or disposed in a relatively close spaced relation to and spaced apart from or disposed within a reference proximity to the feeding pad  300  to overlap the feeding pad  300  such that electromagnetic coupling with the feeding electrode of the feeding pad  300  occurs by coupling electrically to indirectly feed power or signals to the sub antenna  400 , and the remaining part of the sub antenna  400  is formed or disposed relatively distant from the main antenna  100  in substantially perpendicular relation thereto. 
     And, as such, at least one radiating pattern  402  of the sub antenna  400  may be increased in length relative to one or more radiating patterns  101  or  102  of the main antenna  100 . For example, as generally illustrated in  FIG. 4 , the main antenna  100  may be formed or disposed in a generally horizontal direction (H) in the lower portion of the corresponding mobile terminal apparatus  20 , and the sub antenna  400  may be formed or disposed in a generally vertical direction (V) in the left or right side of the mobile terminal apparatus  20 . 
     The exemplary embodiments described in relation to  FIG. 4  above correspond to where a feeding part  404  of the sub antenna  400  is formed or disposed in facing or substantially facing to and spaced apart from or disposed within a reference proximity to the feeding pad  300  of the main antenna  100 , and the radiating pattern  402  of the sub antenna  400  is spaced and generally extends in a direction away from the main antenna  100  in order to minimize interference of the sub antenna  400  with respect to the main antenna  100 . However, the main antenna  100  and the sub antenna  400  may be arranged in any other of various directions or orientations, according to exemplary embodiments of the invention. 
     According to exemplary embodiments referring again to  FIG. 1  and  FIG. 3 , the circuit substrate  200  may include the main PCB  210  formed or disposed in one side of the mobile terminal apparatus  20 , the sub PCB  230  formed or disposed in the other side of the mobile terminal apparatus  20  and may have the feeding pad  300  connected to the main PCB  210  through a cable, such as RF cable  220 , to receive/transmit signals from/to the main PCB  210 . And the ground  240  may be spaced apart from or disposed within a reference proximity to the sub PCB  230  near one edge of the sub PCB  230  so as not to overlap the area of the main antenna  100 . 
     Generally, the mobile terminal apparatus  20  may have the main PCB  210  in the upper portion thereof, and the sub PCB  230  and a battery or other power supply  250  in the lower portion thereof. The main antenna  100  may be positioned over the sub PCB  230 , and the main PCB  210  may be connected to the feeding pad  300  of the sub PCB  230  through the RF cable  220  to transfer power or signals to the main antenna  100  and to the sub antenna  400 . The main antenna  100  may be directly connected to the feeding pad  300 . 
     The sub antenna  400  may be positioned below the sub PCB  230 , and may functions as an antenna by being indirectly fed power or signals through electrical coupling with the feeding pad  300  with the sub PCB  230  positioned in between, instead of being directly connected to the feeding pad  300 . At least one part of the sub antenna  400 , such as feeding part  404 , may be arranged in parallel or substantially parallel relation with the feeding pad  300  to face the feeding pad  300 . Thereby, the sub antenna  400  may operate as an indirect feeding line of the feeding pad  300 . Accordingly, through the arrangement structure of the main antenna  100  and the sub antenna  400 , a multi-band antenna may be implemented according to exemplary embodiments. 
     The ground  240  (See  FIG. 3  and  FIG. 5 , for example) may be generally in the shape of rectangle, and may be formed or disposed separately from the main PCB  210  or the sub PCB  230 . Or, the ground  240  may be integrated into the main PCB  210  or the sub PCB  230  so that the main PCB  210  or the sub PCB  230  itself may function as the ground  240 . The ground  240  may block a radiating beam from the main antenna  100  and may thereby reduce the radiating efficiency of the main antenna  100 . Accordingly, in order to maximize the radiating efficiency of the main antenna  100 , the ground  240  may be formed or disposed relatively close to one edge of the sub PCB  230  while being spaced apart from or disposed within a reference proximity to the sub PCB  230 , such that the ground  240  does not overlap or substantially overlap the main antenna  100 . 
     According to exemplary embodiments, the ground  240  may include a plurality of layers stacked on top of each other, wherein the individual layers may be connected to each other through a via hole or aperture  243 . 
     The ground  240  may include a first ground  241  in the front side of the ground  240 , and a second ground  242  in the rear side of the ground  240 . The second ground  242  may be electrically connected to the first ground  241  through the via hole or aperture  243 . The via hole or aperture  243  may electrically connect the first and second grounds  241  and  242  formed or disposed on the circuit substrate  200  to each other. The via hole or aperture  243  may be formed or disposed by making a hole or aperture with a predetermined or reference diameter at a predetermined or reference location, such as by photo etching of the circuit substrate  200  and plating the via hole or aperture  243 , for example. 
     According to exemplary embodiments, the sub PCB  230  may have a ground pad  500  (See  FIG. 3 , for example) electrically connected to a part of the ground  240  (See  FIG. 1 , for example) through a micro strip line  510 , and the main antenna  100  may be connected to the ground pad  500 , such as by the ground line  120 . 
     The ground pad  500  may be selectively electrically connected or disconnected to or from the ground  240  through the micro strip line  510 . The micro strip line  510  may have a ground in the rear side, and a signal line in the front side to transfer electromagnetic signals However, the micro strip line  510  may be used to selectively electrically connect or disconnect the ground pad  500  from the ground  240 , such as by the processor  212 , without having any signal line or ground to selectively supply power, such as from the power supply  250 , or signals to the main antenna  100 , so as to selectively transmit or receive signals or electromagnetic waves at one or more first frequency bands through the main antenna  100 . The micro strip line  510  may be implemented as a short, thin line with high impedance, whose length may be relatively short compared to the wavelength X in its operating frequency band, for example. 
     Accordingly, signals, or current, or power, such as from power supply  250 , that may be supplied from the main PCB  210  may be transferred to the main antenna  100  through the feeding pad  300 , and the current, or power, or signals may be circulated through the radiating patterns  101  and  102  of the main antenna  100  to reach the other end of the main antenna  100 , and then return to the ground  240  through the ground pad  500 , thereby forming a first transmission path or line for transmitting and receiving electromagnetic waves or signals at the one or more first frequency bands in the air. 
       FIG. 5  is a perspective view showing the main antenna  100 , the sub antenna  400 , the circuit substrate  200 , and an antenna carrier unit  600  of  FIG. 3  according to exemplary embodiments of the present invention. 
     And  FIG. 6  is a cross-section view showing the main antenna  100 , the sub antenna  400 , and the circuit substrate  200  of  FIG. 5  according to exemplary embodiments of the present invention. 
     Referring to  FIGS. 5 and 6 , in the mobile terminal apparatus  20  with the indirect feeding antenna or sub antenna  400 , the antenna carrier unit  600  may be formed or disposed on or over an upper side  232  of the sub PCB  230  to fix the main antenna  100  on the sub PCB  230  of the circuit substrate  200 . The antenna carrier unit  600  may be formed or disposed between the sub PCB  230  and the main antenna  100 . 
     The antenna carrier unit  600  may be in the shape of a generally hollow rectangular parallelepiped such that it can be installed in the mobile terminal apparatus  20 . The antenna carrier unit  600  may have a generally planar board structure spaced apart by a predetermined or reference distance from the sub PCB  230 . And the radiating patterns  101  and  102  of the main antenna  100  may be formed or disposed on the surface of the antenna carrier unit  600  to provide antenna characteristics according to exemplary embodiments. The sub antenna  400  may be formed or disposed on the second or lower surface  202  of the circuit board  200  toward a lower side  231  of the PCB  230 . 
     Also, the antenna carrier unit  600  may be made of a polyethylene resin including a polyolefin, an acrylonitrile butadiene styrene (ABC) resin, a polyvinyl chloride (PVC) resin, a plastic polymer such as a polycarbonate resin, etc., wherein the plastic polymer may have excellent tensile strength and surface elasticity 
     If the radiating patterns  101  and  102  of the main antenna  100  may be formed or disposed on the surface of the antenna carrier unit  600  made of a Polycarbonate resin by pad printing, etc., the radiating patterns  101  and  102  may be prevented from being damaged, due to the relatively excellent surface elasticity of the antenna carrier unit  600 . However, a conductive ink which may be a material used for forming the radiating patterns  101  and  102  may be pressurized during the after process, which may contribute to performance maintenance of the main antenna  100 . 
     According to exemplary embodiments, the sub antenna  400  may be connected to the second ground  242  on the rear side of the main ground  240  to be grounded. 
     Accordingly, current, or power, or signals supplied from the main PCB  210  may be transferred by electrical coupling to the sub antenna  400  through the feeding pad  300  through the indirect feeding, and the current, or power, or signals, may be circulated along the radiating pattern  402  of the sub antenna  400  formed or disposed, such as in a generally linear path or paths, to reach the other end of the sub antenna  400 , and then return to the main ground  240  through the ground line  410  connecting the sub antenna  400  to the ground  240 , thereby forming a second transmission path or line for receiving and transmitting electromagnetic waves or signals at least at one second frequency band in the air. 
       FIG. 7  is a circuit diagram illustrating a mobile terminal apparatus  20  with an indirect feeding antenna or sub antenna  400 , according to exemplary embodiments of the present invention. 
     Referring to  FIG. 7 , the mobile terminal apparatus  20  with the indirect feeding antenna includes the sub antenna  400 , the feeding point or feeding pad  300 , and a switch or switch device  700  for selectively connecting/disconnecting the sub antenna  400  to/from the main ground  240  (See  FIG. 3 , for example) to selectively supply power, such as from the power supply  250 , or signals indirectly through electrical coupling to the sub antenna  400  to indirectly feed power or signals indicated at  412 , so as to selectively transmit or receive signals at the at least one second frequency band. 
     The switching device  700  may be formed or disposed between the sub antenna  400  and the main ground  240  to selectively connect/disconnect the sub antenna  400  to/from the main ground  240 . Since the switch or switching device  700  may be connected to the main ground  240  through a ground line  710 , the switching device  700  may electrically selectively connect/disconnect the sub antenna  400  to/from the main ground  240 . The switching device  700  may be a RF switch device, such as a diode, a transistor, a Field Effect Transistor (FET), a Micro Electro Mechanical Systems (MEMS), and a Complementary Metal Oxide Semiconductor (CMOS) switch device, for example which may perform a switching function using current and voltages, such as from power supply  250  of  FIG. 1 , for example. 
     By selectively turning on/off the switching device  700 , such as by the processor  212 , to selectively connect the sub antenna  400  to the main ground  240 , it may be possible to improve the quality of wireless communication adaptively according to a wireless communication environment including the resonance frequency band of each of the main antenna  100  and the sub antenna  400 . 
     Therefore, in the mobile terminal apparatus with the indirect feeding antenna or sub antenna according to exemplary embodiments described above, by indirectly feeding a sub antenna through electrical coupling with a feeding pad of a main antenna, a resonance may be caused in multiple frequency bands and a wide frequency band range so as to additionally support a desired frequency band, as well as the frequency band of the main antenna and a size of the main antenna may not be increased. 
     Also, since the sub antenna may be formed or disposed in an existing space for the main antenna, it may be unnecessary to increase a size of the mobile terminal to accommodate the sub antenna. 
     In addition, since there may be substantially no interference between the sub antenna and the main antenna, the sub antenna may be selectively used while maintaining the antenna performance of the main antenna, which may thereby increase antenna efficiency according to the characteristics of a given frequency band according to exemplary embodiments. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.