Abstract:
An antenna apparatus for a portable terminal is configured to reduce interference. The antenna apparatus includes a first antenna and a second antenna spaced apart from the first antenna. The antenna apparatus also includes a filter coupled to the first antenna and the second antenna, and configured to increase an isolation between the first antenna and the second antenna by filtering signals transmitted through the first antenna and the second antenna. The antenna apparatus further includes a main board configured to process the filtered signals.

Description:
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY 
       [0001]    The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Sep. 20, 2011 and assigned Serial No. 10-2011-0094642, the entire disclosure of which is hereby incorporated by reference. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to an antenna apparatus for a portable terminal. 
       BACKGROUND OF THE INVENTION 
       [0003]    With the development of electronics communication industries in recent years, a portable terminal has become a necessity of modern life as an important means for delivering information which changes rapidly. Therefore, the portable terminal is developed competitively by those skilled in the art to ensure more users. Further, since a communication service such as Global System for Mobile Communications (GSM), Personal Communications Services (PCS), Digital Multimedia Broadcasting (DMB), Wireless Local Area Network (WLAN), Wireless Broadband (WiBro), Long Term Evolution (LTE), Worldwide Interoperability for Microwave Access (WiMax), 802.11n, and the like, has already been provided, a portable terminal capable of using several communication services without being limited to any specific one service has increased in number. 
         [0004]    In general, a portable terminal includes antennas capable of transmitting and receiving signals of the respective communication services. However, since several antennas are provided in a limited space, interference may occur between the antennas, which results in a problem of performance deterioration.  FIG. 1  illustrates a perspective view of a conventional antenna apparatus. Referring to  FIG. 1 , a conventional antenna apparatus  100  includes a main board  110  for processing signals of respective communication service bands, and first and second antennas  120  and  130  for communicating with the main board  110  and for transmitting and receiving the signals of the respective communication service bands. The first and second antennas  120  and  130  may be attached to the main board  110 , or may be fixed to a molding. To facilitate transmission and reception of the signals of the respective communication services, the two antennas  120  and  130  should be sufficiently spaced apart from each other. However, as illustrated, if the two antennas  120  and  130  are located close to each other, the two antennas  120  and  130  mutually interfere with each other, and disrupt the performance of the portable terminal. 
       SUMMARY OF THE INVENTION 
       [0005]    To address the above-discussed deficiencies of the prior art, it is a primary object to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide an antenna apparatus for a portable terminal capable of reducing mutual interference even if antennas are not placed to be spaced apart from each other. 
         [0006]    Another aspect of the present disclosure is to provide an antenna apparatus for a portable terminal capable of ensuring performance by improving an isolation between neighboring antennas. 
         [0007]    Another aspect of the present disclosure is to provide an antenna apparatus for a portable terminal capable of facilitating transmission and reception of signals in one communication service band or different communication service bands. 
         [0008]    In accordance with an aspect of the present disclosure, an antenna apparatus for a portable terminal is provided. The antenna apparatus includes a first antenna and a second antenna spaced apart from the first antenna. The antenna apparatus also includes a filter coupled to the first antenna and the second antenna, and configured to increase an isolation between the first antenna and the second antenna by filtering signals transmitted through the first antenna and the second antenna. The antenna apparatus also includes a main board configured to process the filtered signals. 
         [0009]    Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
           [0011]      FIG. 1  illustrates a perspective view of a conventional antenna apparatus; 
           [0012]      FIG. 2  illustrates a perspective view of a portable terminal according to an embodiment of the present disclosure; 
           [0013]      FIG. 3  illustrates a block diagram of a portable terminal according to an embodiment of the present disclosure; 
           [0014]      FIG. 4  to  FIG. 11  illustrate a structure of an antenna apparatus according to an embodiment of the present disclosure; 
           [0015]      FIG. 12  illustrates a graph illustrating a Scattering (S) parameter of the conventional antenna apparatus; and 
           [0016]      FIG. 13  illustrates a graph illustrating an S parameter of an antenna apparatus according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIGS. 1 through 13 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Exemplary embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the disclosure in unnecessary detail. Also, the terms used herein are defined according to the functions of the present disclosure. Thus, the terms may vary depending on user&#39;s or operator&#39;s intension and usage. That is, the terms used herein are to be understood based on the descriptions made herein. 
         [0018]    The present disclosure relates to an antenna apparatus for a portable terminal capable of improving an isolation between antennas. The antenna apparatus of the present disclosure does not experience performance deterioration even if antennas are not placed to be spaced apart from each other, and smoothly transmits and receives a signal of a corresponding communication service band. 
         [0019]      FIG. 2  illustrates a perspective view of a portable terminal according to an embodiment of the present disclosure. 
         [0020]    Referring to  FIG. 2 , a portable terminal  20  includes a speaker  21  for outputting an electrical signal into an audio signal, a display  22  for outputting an electrical signal into a video signal, a microphone  24  for converting an audio signal into an electrical signal, and an input key  23 . The display  22  may be a Liquid Crystal Display (LCD), a touch screen in which a touch panel is further attached to the LCD, or any other suitable display. 
         [0021]    The terminal  20  includes an antenna apparatus for performing wireless communication, and has the following structure. The antenna apparatus of the present disclosure includes at least two antennas for transmitting and receiving a signal of a corresponding communication service band and a main board for processing a signal transmitted through the antennas. The main board is a board which contains a basic circuit and components. The main board allows a configuration of an execution environment of the portable terminal and maintains information thereof, allows the portable terminal to operation reliably, and allows to facilitate data input and output exchange of all devices of the portable terminal. The main board includes a communication module for processing signals transmitted through the antennas. 
         [0022]    The antennas are situated at either an upper portion U or a lower portion D of the terminal. Since a user typically grabs a lateral portion of the terminal, it is often not preferable to place the antennas to the lateral portion of the terminal. 
         [0023]    In an embodiment, the antenna apparatus of the present disclosure can ensure its performance even if the antennas are located close to each other since an isolation between the antennas can be improved. The antenna apparatus of the present disclosure includes a filter for removing an interference signal between the antennas, thereby achieving a desired result. The respective antennas of the antenna apparatus of the present disclosure can transmit and receive signals of different communication service bands, or can transmit and receive signals of one communication service band. 
         [0024]      FIG. 3  illustrates a block diagram of a portable terminal according to an embodiment of the present disclosure. 
         [0025]    Referring to  FIG. 3 , a controller  201  includes a modem for processing signals of communication units  202  and  203  to be described below. The communication units  202  and  203  can be implemented as one communication unit such that respective antennas can be processed individually. 
         [0026]    The portable terminal according to this embodiment includes a first antenna  31  for transmitting and receiving a signal of a first communication frequency band and a second antenna  32  for transmitting and receiving a signal of a second communication frequency band. The first antenna  31  is electrically coupled to a first communication unit  202  for processing a signal of a first communication service band, and the second antenna  32  is electrically coupled to a second communication unit  203  for processing a signal of a second communication service band. An antenna having such a structure may be a well-known diversity antenna apparatus or a Multiple Input Multiple Output (MIMO) antenna apparatus. 
         [0027]    In an embodiment, the portable terminal further includes a filter  50  for removing an interference signal generated between the first antenna  31  and the second antenna  32 . Even if the first antenna  31  and the second antenna  32  are located close to each other due to the filter  50 , an isolation between the two antennas can be ensured. The filter  50  has a structure in which the first antenna  31  and the second antenna  32  are electrically coupled, which will be described below in detail with reference to the accompanying drawing. Descriptions on a display unit  204 , a memory  205 , a codex  206 , an input unit  207 , a speaker  21 , and a microphone  24  will be omitted since these components of the terminal are well-known components. 
         [0028]      FIG. 4  to  FIG. 11  illustrate a structure of an antenna apparatus according to an embodiment of the present disclosure. Referring to  FIG. 4  to  FIG. 11 , the antenna apparatus of the present disclosure further includes a filter for removing an interference signal unlike the conventional antenna apparatus. The filter may include a circuit on which at least one of a passive element (e.g., an inductor and a capacitor), an active element (e.g., a diode), and a micro strip line is placed. 
         [0029]    The antenna apparatus illustrated in  FIG. 4  to  FIG. 11  includes antennas which are spaced apart from each other and a main board which is electrically coupled to the antennas and which processes signals transmitted through the antennas. The antennas may be a thin metal film placed on the main board or may be a metal plate attached to a molding fixed to the main board. The antennas have a feeding node through which current is supplied and a ground node for grounding. The feeding node is electrically connected to a feeding line of the main board and the ground node is electrically connected to a around line of the main board. The feeding line is coupled to a communication unit for processing a signal of a corresponding communication service, and the ground line is coupled to a ground. If an element, such as an inductor or capacitor, is not placed to the feeding line or the ground line, a structure in which the feeding node or the ground node is directly coupled to the main board is also possible. 
         [0030]    As described above, the antenna apparatus illustrated in  FIG. 4  to  FIG. 11  includes a first antenna and a second antenna, and the main board constitutes a first feeding line and a first ground line which are electrically coupled to the first antenna and a second feeding line and a second ground line which are electrically coupled to the second antenna. The first feeding line, the first ground line, the second feeding line, and the second ground line do not cross each other. 
         [0031]    The antenna apparatus of  FIG. 4  to  FIG. 6  includes first and second antennas  31  and  32  for transmitting and receiving signals of different communication service bands, and includes a main board  40  for processing signals transmitted through the antennas  31  and  32 . The main board  40  includes a first communication unit (not shown) for performing a first communication service by processing a signal transmitted through the first antenna  31  and a second communication unit (not shown) for performing a second communication service by processing a signal transmitted through the second antenna  32 . The main board  40  constitutes a first feeding line  411  and a first ground line  412  electrically coupled respectively to a feeding node  311  and a ground node  312  of the first antenna  31 . Further, the main board  40  constitutes a second feeding line  421  and a second ground line  422  electrically coupled respectively to a feeding node  321  and a ground node  322  of the second antenna  32 . 
         [0032]    The first and second feeding lines  411  and  421  of the antenna apparatus of  FIG. 4  face each other, with the first ground line  412  and the second ground line  422  in the middle. The filter  50  may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the first ground line  412  or the second ground line  422 . In addition, the filter  50  may include at least one line  423  for coupling the first ground line  412  and the second ground line  422  in a parallel manner, and may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the line  423 . Further, the filter  50  includes at least one line  424  for electrically connecting the first antenna  31  and the second antenna  32 , and may further include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the line  424 . 
         [0033]    The first ground line  412  and the second ground line  422  of the antenna apparatus of  FIG. 5  and  FIG. 6  face each other, with the first feeding line  411  and the second feeding line  421  in the middle. The filter  50  may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the first ground line  412  and the second ground line  422 . In addition, the filter  50  may include at least one line  425  for coupling the first ground line  412  and the second ground line  422  in a serial manner, and may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the line  425  in a parallel or serial manner. 
         [0034]    The antenna apparatus of  FIG. 7  to  FIG. 9  includes first and second antennas  41  and  42  for transmitting and receiving signals of one communication service band, and a main board  45  for processing signals transmitted through the antennas  41  and  42 . The main board  45  further includes one communication unit for performing a corresponding communication service by processing signals transmitted through the two antennas  41  and  42 . In an embodiment, the first and second antennas  41  and  42  are symmetrical to each other. The main board  45  constitutes a first feeding line  511  and a first ground line  512  electrically coupled respectively to a feeding node  411  and a ground node  412  of the first antenna  41 . Further, the main board  45  constitutes a second feeding line  521  and a second ground line  522  electrically coupled respectively to a feeding node  421  and a ground node  422  of the second antenna  42 . 
         [0035]    The first and second feeding lines  511  and  521  of the antenna apparatus of  FIG. 7  face each other, with the first ground line  512  and the second ground line  522  in the middle. The filter  60  may include one or more lines  523  and  524  for coupling the first ground line  512  or the second ground line  522  in a parallel manner, and may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the lines  523  and  524 . Further, the filter  60  includes at least one line for electrically connecting the first antenna  41  and the second antenna  42 , and may further include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the line. 
         [0036]    The first ground line  512  and the second ground line  522  of the antenna apparatus of  FIG. 8  and  FIG. 9  face each other, with the first feeding line  511  and the second feeding line  521  in the middle. The filter  60  may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the first ground line  512  and the second ground line  522 . In addition, the filter  60  may include at least one line  525  for coupling the first ground line  512  and the second ground line  522  in a serial manner, and may include a circuit on which at least one of a passive element, an active element, and a micro strip line is placed to the line  525  in a parallel or serial manner. 
         [0037]    The filters  50  and  60  of the antenna apparatus may be a Band Elimination Filter (BEF) for stopping a signal of a certain frequency band to improve an isolation between antennas. However, the present disclosure is not limited thereto, and thus the antenna apparatus according to embodiments of the present disclosure may further include one of a Low Pass Filter (LPF), a High Pass Filter (HFP), and a Band Pass Filter (BPF) to improve an antenna resonance characteristic in addition to the isolation. 
         [0038]    The antenna apparatus of  FIG. 10  includes first and second antennas  71  and  72  for transmitting and receiving signals of different communication service bands and a main board  80  for processing signals transmitted through the antennas  71  and  72 . The antenna apparatus of the present disclosure illustrated in  FIG. 10  has a similar structure as that of the antenna apparatus of the present disclosure illustrated in  FIG. 4 . The antenna apparatus constitutes a first feeding line  811  and a first ground line  812  which are electrically coupled to the first antenna  71  and a second feeding line  821  and a second ground line  822  which are electrically coupled to the second antenna  72 . However, the first antenna  71  and the second antenna  72  of the antenna apparatus of  FIG. 10  do not additionally constitute a feeding node and a ground node. The present disclosure is not limited thereto, and thus the antenna apparatus consisting of the antennas which do not constitute the feeding node and the ground node may conform to the structure of  FIG. 5  and  FIG. 6 . Importantly, the antenna apparatus of  FIG. 10  constitutes a circuit on which at least one of a passive element, an active element, and a micro strip line is placed. The circuit constitutes a filter  90 . 
         [0039]    The antenna apparatus of  FIG. 11  includes first and second antennas  71  and  72  which are symmetrical to each other and a main board  80  for processing signals transmitted through the antennas  71  and  72 . The antenna apparatus of the present disclosure illustrated in  FIG. 11  has a similar structure as that of the antenna apparatus of the present disclosure illustrated in  FIG. 7 . The antenna apparatus constitutes a first feeding line  811  and a first ground line  812  which are electrically coupled to the first antenna  71  and a second feeding line  821  and a second ground line  822  which are electrically coupled to the second antenna  72 . However, the first antenna  71  and the second antenna  72  of the antenna apparatus of  FIG. 11  do not additionally constitute a feeding node and a ground node. The present disclosure is not limited thereto, and thus the antenna apparatus consisting of the antennas which do not constitute the feeding node and the ground node may conform to the structure of  FIG. 8  and  FIG. 9 . Importantly, the antenna apparatus of  FIG. 11  constitutes a circuit on which at least one of a passive element, an active element, and a micro strip line is placed. The circuit constitutes a filter  90 . 
         [0040]      FIG. 12  illustrates a graph illustrating a Scattering (S) parameter of the conventional antenna apparatus.  FIG. 13  illustrates a graph illustrating an S parameter of an antenna apparatus according to an embodiment of the present disclosure. 
         [0041]    Referring to  FIG. 12 , among S parameters of the conventional antenna apparatus, an isolation has a value −8.88 dB at a predetermined resonance frequency 0.87 GHz. In contrast, referring to  FIG. 13 , among S parameters of the antenna apparatus according to this disclosure, an isolation has a value −19.61 dB at a predetermined resonance frequency 0.885 GHz. The antenna apparatus according to this disclosure shows an improved isolation in comparison with the conventional antenna apparatus. 
         [0042]    In conclusion, the antenna apparatus of the portable terminal according to the present disclosure can ensure its performance by reducing mutual interference between antennas. 
         [0043]    While the present disclosure has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims.